Genetic Variability and Recombination of the NSP2 Gene of PRRSV-1 Strains in China from 1996 to 2022

Genetic Variability and Recombination of the NSP2 Gene of PRRSV-1 Strains in China from 1996 to 2022 | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Genetic Variability and Recombination of the NSP2 Gene of PRRSV-1 Strains in China from 1996 to 2022 Hang Zhang, Qin Luo, Yajie Zheng, Huiyang Sha, Gan Li, Weili Kong, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3012980/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Porcine reproductive and respiratory syndrome (PRRS) has been present in China for over 20 years. Due to the continuous mutation of PRRS virus (PRRSV), it causes significant economic losses to the pig industry annually. This study aimed to understand the genetic variation of the PRRSV-1 NSP2 gene in China. A total of 69 PRRSV-1 NSP2 strains, consisting of 25 Chinese and 44 foreign strains, were collected and their nucleotide and amino acid homology were analyzed. Results indicated that the nucleotide homology of NSP2 ranged 42.1–97.0%, while the amino acid homology ranged from 59.4–100.0%. Multiple sequence alignments of NSP2 amino acids from the 69 PRRSV-1 strains were conducted to compare differential sites of NSP2 amino acids between PRRSV-1 and PRRSV-2. The study revealed that PRRSV-1 had more missing and replaced sites compared to PRRSV-2. A phylogenetic analysis of the NSP2 sequence of 90 PRRSV strains revealed that the genetic relationships between BJEU06-1-like and NMEU09-1-like are relatively close, but far from Amervac-like and HKEU-16-like. Additionally, recombinant analysis showed that four recombination events occurred in the 90 selected PRRSVs, with two occurring in the Chinese PRRSV-1 NSP2 sequence. These findings provide a deeper understanding of the prevalence of PRRSV-1 in China over the past 20 years and will serve as a theoretical basis for the evolution and epidemiology of PRRSV.The abstract serves both as a general introduction to the topic and as a brief, non-technical summary of the main results and their implications. Authors are advised to check the author instructions for the journal they are submitting to for word limits and if structural elements like subheadings, citations, or equations are permitted. Genetic variability recombination PRRSV-1 NSP2 gene China Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1 Introduction Porcine reproductive and respiratory syndrome (PRRS) is a highly contagious disease caused by the porcine reproductive and respiratory syndrome virus (PRRSV). Since its first report in 1987, PRRS has resulted in significant economic losses of up to $ 600 million per year in the United States (approximately $ 1.8 million per day). In China the losses have been even higher, primarily due to secondary infections from other diseases such as swine fever, pseudorabies, and bacterial diseases like porcine infectious pleuropneumonia [ 1 ]. In 1991 and 1992, two strains of Lelystad virus and VR2332 were isolated from infected pigs in Europe and America, respectively. These strains were classified into two genotypes, PRRSV-1 and PRRSV-2, based on their antigenic differences [ 2 , 3 ]. PRRSV-1 and PRRSV-2 are currently classified as two species, Betaarterivirus suid 1 and Betaarterrus suid 2, respectively. The first isolation of type 2 PRRSV was in Harbin, China in 1996 and it was named CH-1a. The entire genome sequence of Ch-1a was uploaded to GenBank in the same year with login number AY032626 [ 4 ]. Type 1 PRRSV, also known as B13, was initially discovered in Beijing, China in 1997. However, only its ORF5 gene was uploaded to GenBank in 2004 with the login number AY633973 [ 5 ]. Currently, PRRSV-2 is predominantly found in North America and Asia, with PRRSV-1 also being present. South America only has PRRSV-2, while Europe mostly relies on PRRSV-1. However, PRRSV-2 is also found in Western Europe. PRRSV has not yet been reported in Australia. As of 2022, the occurrence and prevalence of PRRS globally has remained stable. PRRSV is a single-stranded positive-sense RNA virus with a capsule. Its genome consists of 11 open reading frames (ORFs) and has a length of 15 kb and, namely ORF1a, ORF1b, ORF2a, ORF2b, ORF3-7, ORF5a, and ORF1aTF, that overlaps the non-structural protein (NSP)2-coding region of ORF1a [ 6 ]. Among them, ORF1a and ORF1aTF translationally encode at least 12 NSPs, including NSP1α, NSP1β, NSP2 and its related proteins (NSP2N and NSP2TF), NSP3, NSP4, NSP5, NSP6, NSP7α, NSP7β and NSP8; NSP2 at 2.9 kb in length is the longest [ 7 ]. NSP2 and ORF5 are highly variable and ORF5 is associated with the neutralizing epitope. They are usually used as target genes for PRRSV molecular epidemiology surveillance [ 8 , 9 ]. PRRSV NSP2 is not only associated with the genetic variation but also plays a role in multiple biological processes as a multifunctional protein. A comprehensive understanding of NSP2 can greatly contribute to the elucidation of the pathogenesis of this disease. In their study, Shi et al. conducted a phylogenetic analysis on ORF5 sequences available in GenBank and identified three subtypes of PRRSV-1: Subtype I (Global, Russian), Subtype II (Russian, Lithuania, Belarus), and Subtype III [ 10 ]. Subtype I of PRRSV-1 was initially detected in several countries in Western Europe and has since spread to Asia and the Americas. It has 12 evolutionary branches. On the other hand, Subtype II and Subtype III are mainly found in Eastern Europe and Russia. In China, the majority of PRRSV-1 isolates are Subtype I Global. In 2017, Chen et al. classified PRRSV-1 into four gene subgroups in China, namely Amervac-like, BJEU06-1-like, HKEU-16-like, and NMEU09-1-like [ 11 ]. Due to the prevalence of PRRSV-2 in China, most research on NSP2 has focused on this strain. However, there has been an increase in the occurrence of PRRSV-1 in recent years, indicating a need for further investigation into NSP2 and its role in this strain as well [ 12 – 14 ]. This study aims to understand the genetic variation of NSP2 protein in the classic strain NSP2 of PRRSV-1. It does this by comparing the nucleotide and amino acid homology, conducting multiple sequence alignment of amino acids, analyzing the phylogenetic relationship of NSP2 gene, and finally conducting recombination analysis. The findings of this study can help in timely monitoring of the future epidemic trend of PRRSV-1. 2 Materials and Methods 2.1 The Dataset A total of 25 Chinese PRRSV-1 strains (including Amervac-like, BJEU06-1-like, HKEU-16-like, and NMEU09-1-like gene subgroups), 44 foreign PRRSV-1 strains, and 21 PRRSV-2 strains (including lineages 1, 3, 5, and 8) were carefully selected from the GenBank database of the NCBI website (Table 1 ). The selection criteria were based on the inclusion of strains from different years ranging from 1996 to the present, representation of commonly reported PRRSV strains in literature, and the inclusion of commonly used PRRSV-1 vaccine strains.The Dataset 2.2 Nucleotide homology analysis of PRRSV-1 NSP2 To determine the homology between nucleotide sequences of PRRSV-1 NSP2, this study analyzed 69 PRRSV-1 strain NSP2 sequences using the Cluster W method in the MegAlign function of DNAStar software (version 7.0, Madison, WI). The resulting analysis was presented using Sequence Distances. 2.3 Amino acid homology analysis of PRRSV-1 NSP2 To determine the homology between the amino acid sequences of PRRSV-1 NSP2, we translated the above 69 strains of nucleotides into amino acid sequences. The amino acid sequences were analyzed using the Cluster W method in the MegAlign function of DNAStar software (version 7.0, Madison, WI), and the analysis results were displayed using Sequence Distances. 2.4 Alignment of PRRSV-1 NSP2 Amino Acid Sequences In order to compare the differences in NSP2 amino acid sites between PRRSV-1 and PRRSV-2, this study utilized 34 PRRSV-1 and six PRRSV-2 NSP2 sequences from Table 1 for multiple sequence alignment. The sequences were imported into GENEDOC software (version 2.7) for amino acid sequence alignment. 2.5 Phylogenetic Analysis The NSP2 gene phylogenetic analysis was conducted using the sequence information of 90 PRRSV strains as presented in Table 1 . The analysis involved the Cluster W method in the MegAlign function of DNAStar software (version 7.0, Madison, WI), followed by 1000 boot repetitions using the Neighbor Connection (NJ) method of MEGA software (version 7.0.26, Mega Limited, Auckland, New Zealand). Further analysis was conducted using the maximum likelihood (ML) method of PhyloSuite software (version 1.2.2) with 1000 bootstrap repetitions. The resulting phylogenetic tree was annotated using the online software The Interactive Tree Of Life ( https://itol.embl.de ). 2.6 Recombination Analysis To perform recombination analysis, import the processed sequences into RDP (version 4.0) software and use seven methods (RDP, MaxChi, GeneConv, BootScan, SiScan, 3Seq, and Chimaera) with default settings. Only recombination events confirmed by at least 5 of the 7 methods and a p-value threshold of 0.05 are reported. The identified strain is considered a recombinant strain. Additionally, SimPlot (version 3.5.1) was used to confirm the detected recombination events. Table 1 The reference sequence of PRRSV NSP2 strains. Year Aera sequence Strain Genbank Accession number Type 2003 China NSP2 HK3 KF287129 PRRSV-1 2004 China NSP2 HK5 KF287130 PRRSV-1 2004 China NSP2 HK8 KF287128 PRRSV-1 2004 China NSP2 HK10 KF287131 PRRSV-1 2006 China NSP2 BJEU06-1 GU047344 PRRSV-1 2007 China NSP2 HKEU16 EU076704 PRRSV-1 2009 China NSP2 SHE GQ461593 PRRSV-1 2009 China NSP2 NMEU09-1 GU047345 PRRSV-1 2011 China NSP2 GZ11-G1 KF001144 PRRSV-1 2011 China NSP2 NVDC-FJ KC492506 PRRSV-1 2011 China NSP2 NVDC-NM1 JX187609 PRRSV-1 2011 China NSP2 NVDC-NM2 KC492504 PRRSV-1 2011 China NSP2 NVDC-NM3 KC492505 PRRSV-1 2012 China NSP2 LNEU12 KM196101 PRRSV-1 2013 China NSP2 FJEU13 KP860912 PRRSV-1 2014 China NSP2 FJQEU14 KP860913 PRRSV-1 2014 China NSP2 HLJB1 KT224385 PRRSV-1 2015 China NSP2 15HEN1_EU KX967492 PRRSV-1 2017 China NSP2 HENZMD-10 KY363382 PRRSV-1 2018 China NSP2 KZ2018 MN550991 PRRSV-1 2018 China NSP2 EUGDHD2018 MK639926 PRRSV-1 2018 China NSP2 NPUST-2789-3W-2 MN242825 PRRSV-1 2020 China NSP2 SC-2020-1 MW115431 PRRSV-1 2020 China NSP2 TZJ226 OP566682 PRRSV-1 2020 China NSP2 TZJ637 OP566683 PRRSV-1 1991 Netherlands NSP2 Lelystad virus M96262 PRRSV-1 1992 Belgium NSP2 BE_92V058 MW448197 PRRSV-1 1996 Belgium NSP2 96V198 MK876228 PRRSV-1 1999 Netherlands NSP2 MLV-DV KJ127878 PRRSV-1 2001 USA NSP2 SD-01-08 DQ489311 PRRSV-1 2003 USA NSP2 EuroPRRSV AY366525 PRRSV-1 2003 Belgium NSP2 BE_03V140 MW053394 PRRSV-1 2004 Netherlands NSP2 PRRSV LV4.2.1 AY588319 PRRSV-1 2006 United Kingdom NSP2 215-06 OP047897 PRRSV-1 2007 Belarus NSP2 Lena JF802085 PRRSV-1 2008 Belgium NSP2 BE_08V156 MW053397 PRRSV-1 2008 Belarus NSP2 lena JF802085 PRRSV-1 2009 Spain NSP2 Amervac PRRS GU067771 PRRSV-1 2010 Belarus NSP2 SU1-Bel KP889243 PRRSV-1 2011 South Korea NSP2 D40 MZ287330 PRRSV-1 2012 Germany NSP2 GER12-720789 OP529852 PRRSV-1 2013 Russia NSP2 WestSib13 KX668221 PRRSV-1 2013 Belgium NSP2 13V117 KT159249 PRRSV-1 2013 Belgium NSP2 BE_13V246 MW053396 PRRSV-1 2013 Belgium NSP2 BE_13V173 MW053395 PRRSV-1 2013 Belgium NSP2 13V091 KT159248 PRRSV-1 2013 Belgium NSP2 BE_13V200 MW053399 PRRSV-1 2013 Belgium NSP2 BE_13V153 MW053398 PRRSV-1 2013 Spain NSP2 ES13-49_P85 MK024325 PRRSV-1 2013 Belgium NSP2 BE_13V264 MW053400 PRRSV-1 2014 Germany NSP2 DE14-3073_P85 MK024324 PRRSV-1 2014 Denmark NSP2 Porcilis_DV-MLV MT311646 PRRSV-1 2014 Belgium NSP2 BE_14V023 MW053401 PRRSV-1 2014 Poland NSP2 PL14-02_P85 MK024327 PRRSV-1 2014 Italy NSP2 PR40/2014 MF346695 PRRSV-1 2014 Italy NSP2 IT14-32_P85 MK024326 PRRSV-1 2015 South Korea NSP2 JB15-E-M17-JB MZ287329 PRRSV-1 2015 South Korea NSP2 JB15-E-P47-GB MZ287328 PRRSV-1 2016 South Korea NSP2 CBNU0495 MZ287327 PRRSV-1 2016 France NSP2 PRRS-FR-2016-56-11-1 MH018883 PRRSV-1 2016 Hungary NSP2 HU19401/2016 MH463457 PRRSV-1 2016 Hungary NSP2 HU24924/2016 MH463459 PRRSV-1 2016 Hungary NSP2 HU19483/2016 MH463458 PRRSV-1 2016 Hungary NSP2 HU18861/2016 MH463456 PRRSV-1 2016 Hungary NSP2 HU18755/2016 MH463455 PRRSV-1 2016 Russia NSP2 Tyu16 MT008024 PRRSV-1 2019 South Korea NSP2 JBNU-19-E01 MW847781 PRRSV-1 2019 Denmark NSP2 DK-2019-10166-107 MN603982 PRRSV-1 2022 Austria NSP2 AUT22-97 OP627116 PRRSV-1 1992 USA NSP2 VR2332 EF536003.1 PRRSV-2 1996 China NSP2 BJ-4 AF331831 PRRSV-2 2003 China NSP2 HN1 AY457635.1 PRRSV-2 2008 China NSP2 PRRSV01 FJ175687 PRRSV-2 2009 China NSP2 SD1-100 GQ914997 PRRSV-2 2012 China NSP2 HZ-31 KC445138 PRRSV-2 1996 China NSP2 CH-1a AY032626 PRRSV-2 2006 China NSP2 TJ EU860248 PRRSV-2 2006 China NSP2 HUB1 EF075945 PRRSV-2 2006 China NSP2 JXA1 EF112445 PRRSV-2 2006 China NSP2 HUN4 EF635006.1 PRRSV-2 2010 China NSP2 QY2010 JQ743666 PRRSV-2 2011 China NSP2 GM2 JN662424 PRRSV-2 2011 China NSP2 QYYZ JQ308798 PRRSV-2 2012 China NSP2 FJFS KP998476 PRRSV-2 2015 China NSP2 GDsg KX621003 PRRSV-2 2013 China NSP2 JL580 KR706343.1 PRRSV-2 2013 China NSP2 FJW05 KP860911 PRRSV-2 2015 China NSP2 HNjZ15 KT945017 PRRSV-2 2015 China NSP2 FJZ03 KP860909 PRRSV-2 2017 China NSP2 NADC30 MH500776.1 PRRSV-2 3 Results 3.1 Nucleotide Similarity This study aimed to investigate the genetic variation of NSP2 gene in PRRSV-1 by analyzing 25 Chinese PRRSV-1 and 44 foreign PRRSV-1 NSP2 sequences for nucleotide homology. The results indicated that the nucleotide similarity of PRRSV-1 NSP2 ranged from 42.1–97.0% (Fig. 1 ). The highest similarity was found between Amervac PRRS-2009 and SHE-2009, at 97.0%, while the lowest similarity was observed between BE_14V023-2014 and Tyu16-2016, at 42.1%. 3.2 Amino Acid Sequence Similarity After comparing the nucleotide similarity of PRRSV-1 NSP2, we translated the nucleotide sequences of 69 NSP2 strains into amino acids for homology analysis. The results indicated that the amino acid similarity of PRRSV-1 NSP2 ranged from 59.4–100.0% (Fig. 2 ). The highest similarity was found between BE_08V156-2008 and Lena-2007, BE_08V156-2008 and lena-2008, as well as Lena-2007 and lena-2008, at 100.0%, while the lowest similarity was observed between PR40-2014 and WestSib13-2013, at 59.4%. 3.3 Amino Acid Sequence Alignment To compare the variation in NSP2 amino acid sequences between PRRSV-1 and PRRSV-2, this study selected 34 PRRSV-1 and six PRRSV-2 NSP2 sequences for multiple sequence alignment. The results showed that PRRSV-1 NSP2 amino acids had more missing sites compared to PRRSV-2 (as indicated by the red box in Fig. 3 ), and the similarity of PRRSV-1 NSP2 was lower. The missing sites were mainly concentrated at positions 30–40, 150–153, 190–200, 215–220, 240–250, 510–520, 530–580, 620–623, and 790–820 amino acids. The regions with higher mutation rates were mainly concentrated at positions 10–30, 300–410, 420–480, 750–780, and 820–850 amino acids. The variation of NSP2 between PRRSV-1 showed no regularity, with the most significant loss of NSP2 at sites 288–463. 3.4 Phylogenetic Analysis To demonstrate the phylogenetic relationship of the PRRSV-1 NSP2 gene, this study analyzed NSP2 sequences of 90 PRRSVs using the NJ method of MEGA software (version 7.0) and the ML method of PhyloSuite software (version 1.2.2) to construct a phylogenetic tree. The results indicate that PRRSV-1 and PRRSV-2 belong to two different evolutionary branches (Figs. 4 and 5 ). Additionally, the genetic relationships between BJEU06-1-like and NMEU09-1-like in PRRSV-1 are closer, while the genetic relationships with Amervac-like and HKEU-16-like are farther. The vaccine strains Amervac PRRS-2009 and SHE-2009 show relatively close genetic relationships in both algorithms. Similarly, the vaccine strains MLV-DV-1999 and Porcilis_DV-MLV-2014 show a relatively close genetic distance to the European representative Lelystad virus. 3.5 Recombinant Analysis This study aimed to gain a better understanding of the genetic evolution of the PRRSV-1 NSP2 gene, through recombination analysis of the NSP2 sequences of 90 collected PRRSV strains. The analysis, conducted using RDP (version 4.0), revealed a total of four potential recombination events in the NSP2 sequence of the 90 PRRSV strains. All four recombination events were supported by more than five algorithms, indicating high reliability and statistical significance (P < 0.05). The results of the analysis are presented in Table 2 and Fig. 6 . In event 1, the primary and secondary parental strains of the recombinant strain HU18755-2016 are JB15-E-P47-GB-2015 and HU18861-2016, respectively; In event 2, the primary and secondary parental strains of the recombinant strain NVDC-NM1-2011 are HENZMD-10 2017 and BJEU06-1 2006, respectively; In event 3, the primary and secondary parent strains of the recombinant strain 13V091-2013 are NMEU09-1-2009 and HU18861-2016, respectively; In event 4, the primary and secondary parent strains of the recombinant strain HKEU16-2007 are HK5-2004 and HK10-2004, respectively. To verify the four recombination events obtained, we used Simplot (version 3.5.1) and the results showed that all four potential recombination events are valid (Fig. 7 ). Out of these four recombinant events, only NVDC-NM1-2011 and HKEU16-2007 are PRRSVs from China, while HU18755-2016 and 13V091-2013 are PRRSVs from other countries. Table 2 Recombination analysis of NSP2 gene. Recombination event Recombinant strains Main parental strain Minor parental strain Recombinant breakpoint Recombination analysis method 1 HU18755-2016 JB15-E-P47-GB-2015 HU18861-2016 35 ~ 2567 (667 ~ 837) RDP(P = 1.517×10 − 22 ) GENECONV(P = 1.203×10 − 25 ) BootScan(P = 1.290×10 − 26 ) MaxChi(P = 2.041×10 − 13 ) Chimaera(P = 3.549×10 − 9 ) SiScan(P = 8.274×10 − 25 ) 3seq (P = 1.583×10 − 8 ) 2 NVDC-NM1-2011 HENZMD-10-2017 BJEU06-1-2006 35 ~ 2504 (1142 ~ 1212) RDP(P = 5.108×10 − 20 ) GENECONV(P = 9.576×10 − 18 ) BootScan(P = 1.451×10 − 28 ) MaxChi(P = 6.927×10 − 18 ) Chimaera(NS) SiScan(P = 1.591×10 − 36 ) 3seq (P = 2.136×10 − 7 ) 3 13V091-2013 NMEU09-1-2009 HU18861-2016 1449 ~ 1615 (947 ~ 2050) RDP(P = 3.072×10 − 2 ) GENECONV(NS) BootScan(P = 2.299×10 − 3 ) MaxChi(P = 4.189×10 − 5 ) Chimaera(1.268×10 − 4) SiScan(P = 1.043×10 − 7 ) 3seq (P = 2.846×10 − 4 ) 4 HKEU16-2007 HK5-2004 HK10-2004 954 ~ 1062 (1206 ~ 1406) RDP(NS) GENECONV(P = 1.797×10 − 2) BootScan(P = 2.727×10 − 2 ) MaxChi(P = 1.748×10 − 2 ) Chimaera(1.337×10 − 2) SiScan(P = 4.185×10 − 2 ) 3seq (P = 2.443×10 − 2 ) 4 Discussion PRRS is a significant infectious diseases that affects the global pig industry due to the susceptibility of PRRSV genome to mutation, which can lead to immune escape [ 15 ]. The main epidemic strain in China is PRRSV-2, and current domestic vaccines mainly target this strain. Therefore, most research focuses on PRRSV-2. However, the detection rate of PRRSV-1 has been increasing in different regions of China in recent years. Multiple regions, such as 22 provinces including Fujian, Zhejiang, Guizhou, Hong Kong, Liaoning, Heilongjiang, and Henan, have reported the detection of PRRSV-1 [ 16 ]. Monitoring the epidemic trend of PRRSV-1 is crucial for preventing and controlling its occurrence. NSP2, the most mutated non-structural protein in PRRSV, plays a vital role in virus replication, transcription, and regulation of host immune response by interacting with host proteins. [ 17 ]. The NSP2 gene exhibits multiple mutation modes, including deletion, recombination, and insertion leading to significant differences in the size of NSP2 gene fragments [ 18 ]. Due to this, NSP2 is often used as a target gene for analyzing genetic variation and evolution of PRRSV. In this study, only a limited number of Chinese PRRSV-1 sequences were available from NCBI, some of which only had ORF5 sequences. Therefore, we collected a total of 25 Chinese PRRSV-1 NSP2 sequences to better understand the differences between PRRSV-1 in China and foreign countries. To expand our analysis, we also selected 44 NSP2 sequences of PRRSV-1 isolated from abroad, resulting in a total of 69 PRRSV-1 sequences analyzed for nucleotide and amino acid homology. The results showed that the nucleotide and amino acid homology ranged from 42.1–97.0% and 59.4–100.0%, respectively. In comparison, the nucleotide and amino acid homology of PRRSV-2 NSP2 reported by Zhang et al. were 72.5–99.8% and 63.9–99.4%, respectively [ 19 ]. The study reveals that PRRSV-1 NSP2 has lower nucleotide and amino acid homology than PRRSV-2, indicating a higher tendency for mutation. To understand the differences in NSP2 amino acid sites between PRRSV-1 and PRRSV-2, the study conducted multiple sequence alignments of 34 and six PRRSV-2 NSP2 sequences, respectively. The results suggest that PRRSV-1 NSP2 has more deletions and replacement sites compared to PRRSV-2. Furthermore, the deletion sites of PRRSV-1 NSP2 are more irregular, which poses a significant challenge for PRRSV-1 vaccine research. In 2020, Zhang et al. discovered a 6 aa deletion (aa357-360 + aa411 + aa449) in the NSP2 region of a PRRSV-1 strain named KZ2018 [ 20 ]. This study dentified that 13V091-2013, BE_13V153-2013, and HU18755-2016 have the same deletion pattern in the NSP2 region, which can serve as a reference for NSP2 gene classification in PRRSV-1. The NSP2 sequences of 90 PRRSV strains were then subjected to phylogenetic analysis using the NJ and ML methods of MEGA (version 7.0) and Simplot (version 3.5.1) software. The analysis revealed that PRRSV-1 contains closely related BJEU06-1-like and NMEU09-1-like viruses, which are located in the same evolutionary branch. However, Amervac-like and HKEU-16-like strains were found to be genetically distant from them. The genetic relationship between BJEU06-1-like and NMEU09-1-like was relatively close based on the phylogenetic tree of the ORF5 gene reported by Li et al., although they were not in the same branch. Similarity, the genetic relationship between HKEU-16-like and NMEU09-1-like was also relatively close. However, the whole genome-based phylogenetic trees showed different results, with BJEU06-1-like having a closer genetic relationship with HKEU-16-like, and Amervac-like having a closer genetic relationship with NMEU09-1-like [ 21 ]. The reason for this difference may be that there is a notable variation in the PRRSV-1 NSP2 gene, but despite this difference, each strain falls under the same branch as the ORF5 based whole genome sequence. As a result, the findings of this research can serve as a valuable point of reference for the categorization of PRRSV-1 based on the NSP2 gene. This study analyzed 90 PRRSV-1 NSP2 sequences and identified four potential recombination events, of which only two were found in China. Both recombination strains had Chinese parent strains. No recombination was detected between vaccine and wild strains in this study. However, it is worth noting that in a previous study by Chen et al. in 2022, [ 22 ] the HLJB1 isolate was found to be the result of recombination between the Amervac vaccine strain and the BJEU06-1 strain. This discrepancy may be due to the fact that Chen et al. analyzed the full-length sequence for recombination, while this study focused only on NSP2 sequence. PRRSV is known for its high mutation rate, particularly in the ORF5 gene, which makes it prone to recombination or mutation events. In contrast, the NSP4 gene is relatively conservative [ 23 ], while NSP2, like ORF5, shows high variability, as confirmed by the results of this study. PRRSV-2 and PRRSV-1 were first reported in China in 1996 and 1997, respectively [ 4 , 5 ]. Despite the one-year difference, there has been a significant disparity in the prevalence of the two types of PRRSVs over the past 20 years. PRRSV-2 has undergone several highly pathogenic PRRS outbreaks [ 24 ], including lineage 3 represented by QYYZ [ 25 ], NADC30 like [ 26 ], and the current NADC34 outbreak [ 27 ]. PRRSV-1 has always been endemic and sporadic, spreading throughout central, northern, southern, eastern, northeastern, and southwestern regions of China [ 28 , 29 ]. The virulence of PRRSV-2 has evolved from low to high pathogenicity, while the virulence of PRRSV-1 is relatively mild, mainly manifested in reproductive disorders in sows and some cases of fever and respiratory difficulties [ 30 ]. In China, vaccination is an important method for preventing and controlling PRRS. Domestic vaccines primarily target PRRSV-2 [ 31 ], while vaccines targeting PRRSV-1 include Porcilis PRRS (Merck), UNISTRAIN PRRS (Hipra), Ingelvac PRRSFLEX EU (Boehringer Ingelheim), ReproCyc PRRS EU (Boehringer Ingelheim), and Suvaxyn PRRS MLV (Zoetis) from abroad. The use of attenuated live vaccines not only poses a risk of returning to strong virulence, but may also cause recombination with wild strains, making prevention and control more difficult. Despite over 20 years of research, PRRSV remains a mystery and a successful prevention and eradication strategy has yet to be found. Although there is a deep understanding of the clinical pathogenesis, molecular epidemiology, virus proliferation, pathogenesis, immune response, and immune escape mechanism of PRRSV, timely monitoring of genetic variations in PRRSV can serve as a reference for effective control of PRRS in China in the future. 5 Conclusions Between 1996 and 2022, PRRSV-1 isolates in China have been classified into four gene subgroups: Amervac like, BJEU06-1-like, HKEU-16-like, and NMEU09-1-like. Studies have shown that the NSP2 sequence of PRRSV-1 displays more variation, deletion, and replacement regions compared to PRRSV-2. However, the recombination rate of the NSP2 region of PRRSV-1 is lower than that of PRRSV-2. Declarations Author Contributions: Writing—original draft preparation, H.Z. and Q.L.; writing—review and editing, Y.Z. and H.S.; software, G.L.; methodology, W.K.; funding acquisition, L.H.; visualization, M.Z. All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by National Natural Science Foundation of China (31902279). Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: All datasets are available in the main manuscript. The dataset supporting the conclusions of this article is included within the article. Conflicts of Interest: The authors declare no conflict of interest. References Brashishkite DA, Galetsky SA, Kuliffay P, Lizonova A, Tatosyan AG, Urbancikova M, Kisselyov FL, Grofova M. BrdU-induced changes in the provirus of PR-RSV in mammalian cells. Neoplasma. 1988;35:643–50. Wensvoort G, Terpstra C, Pol JM, ter Laak EA, Bloemraad M, de Kluyver EP, Kragten C, van Buiten L, den Besten A, Wagenaar F, et al. Mystery swine disease in The Netherlands: the isolation of Lelystad virus. Vet Q. 1991;13:121–30. Benfield DA, Nelson E, Collins JE, Harris L, Goyal SM, Robison D, Christianson WT, Morrison RB, Gorcyca D. Chladek, D. Characterization of swine infertility and respiratory syndrome (SIRS) virus (isolate ATCC VR-2332). J Vet Diagn Invest. 1992;4:127–33. Snijder EJ, Meulenberg JJ. The molecular biology of arteriviruses. J Gen Virol. 1998;79:961–79. Chen J, Liu T, Zhu CG, Jin YF, Zhang YZ. Genetic variation of Chinese PRRSV strains based on ORF5 sequence. Biochem Genet. 2006;44:425–35. Fang Y, Treffers EE, Li Y, Tas A, Sun Z, van der Meer Y, de Ru AH, van Veelen PA, Atkins JF, Snijder EJ, Firth AE. Efficient – 2 frameshifting by mammalian ribosomes to synthesize an additional arterivirus protein. Proc Natl Acad Sci U S A. 2012;109:2920–8. Johnson CR, Griggs TF, Gnanandarajah J, Murtaugh MP. Novel structural protein in porcine reproductive and respiratory syndrome virus encoded by an alternative ORF5 present in all arteriviruses. J Gen Virol. 2011;92:1107–16. Li P, Shen Y, Wang T, Li J, Li Y, Zhao Y, Liu S, Li B, Liu M, Meng F. Epidemiological survey of PRRS and genetic variation analysis of the ORF5 gene in Shandong Province, 2020–2021. Front Vet Sci. 2022;9:987667. Luo Q, Zheng Y, Zhang H, Yang Z, Sha H, Kong W, Zhao M. Wang, N. Research Progress on Glycoprotein 5 of Porcine Reproductive and Respiratory Syndrome Virus. Animals (Basel); 2023. p. 13. Shi M, Lam TT, Hon CC, Hui RK, Faaberg KS, Wennblom T, Murtaugh MP, Stadejek T, Leung FC. Molecular epidemiology of PRRSV: a phylogenetic perspective. Virus Res. 2010;154:7–17. Chen N, Liu Q, Qiao M, Deng X, Chen X, Sun M. Whole genome characterization of a novel porcine reproductive and respiratory syndrome virus 1 isolate: Genetic evidence for recombination between Amervac vaccine and circulating strains in mainland China. Infect Genet Evol. 2017;54:308–13. Sun Q, Xu H, Li C, Gong B, Li Z, Tian ZJ, Zhang H. Emergence of a novel PRRSV-1 strain in mainland China: A recombinant strain derived from the two commercial modified live viruses Amervac and DV. Front Vet Sci. 2022;9:974743. Hsueh FC, Kuo KL, Hsu FY, Wang SY, Chiu HJ, Wu MT, Lin CF, Huang YH, Chiou MT, Lin CN. Molecular Characteristics and Pathogenicity of Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) 1 in Taiwan during 2019–2020. Life (Basel), 2023. 13. Wang X, Bai X, Wang Y, Wang L, Wei L, Tan F, Zhou Z, Tian K. Pathogenicity characterization of PRRSV-1 181187-2 isolated in China. Microb Pathog, 2023. 106158. An TQ, Li JN, Su CM, Yoo D. Molecular and Cellular Mechanisms for PRRSV Pathogenesis and Host Response to Infection. Virus Res. 2020;286:197980. Chen N, Xiao Y, Ye M, Li X, Li S, Xie N, Wei Y, Wang J, Zhu J. High genetic diversity of Chinese porcine reproductive and respiratory syndrome viruses from 2016 to 2019. Res Vet Sci. 2020;131:38–42. Zhang H, Sha H, Qin L, Wang N, Kong W, Huang L, Zhao M. Research Progress in Porcine Reproductive and Respiratory Syndrome Virus-Host Protein Interactions. Anim (Basel), 2022. 12. Yu LX, Wang X, Yu H, Jiang YF, Gao F, Tong W, Li LW, Li HC, Yang S, Chen PF, Yang DQ, Zhang WC, Tong GZ, Zhou YJ. The emergence of a highly pathogenic porcine reproductive and respiratory syndrome virus with additional 120aa deletion in Nsp2 region in Jiangxi, China. Transbound Emerg Dis. 2018;65:1740–8. Zhang H, Luo Q, Zheng YJ, Sha HY. Genetic Variability and Recombination of the NSP2 gene of PRRSV-2 Strains in China from 1996 to 2021. Vet Sci. 2023;10:325. Zhang Q, Song Z, Yu Y, Huang J, Jiang P, Shan H. Genetic analysis of a porcine reproductive and respiratory syndrome virus 1 strain in China with new patterns of amino acid deletions in nsp2, GP3 and GP4. Microb Pathog. 2020;149:104531. Li C, Xu H, Zhao J, Gong B, Sun Q, Xiang L, Li W, Guo Z, Li J, Tang YD, Leng C, Peng J, Wang Q, An T, Cai X, Tian ZJ, Zhou G, Zhang H. Epidemiological investigation and genetic evolutionary analysis of PRRSV-1 on a pig farm in China. Front Microbiol. 2022;13:1067173. Chen N, Cao Z, Yu X, Deng X, Zhao T, Wang L, Liu Q, Li X, Tian K. Emergence of novel European genotype porcine reproductive and respiratory syndrome virus in mainland China. J Gen Virol. 2011;92:880–92. Sha H, Zhang H, Luo Q, Zheng Y, Zhu Q, Wang N, Qin L, Li H, Huang L, Zhao M. Variations in the NSP4 gene of the type 2 porcine reproductive and respiratory syndrome virus isolated in China from 1996 to 2021. Virus Genes. 2023;59:109–20. Zhou Z, Ni J, Cao Z, Han X, Xia Y, Zi Z, Ning K, Liu Q, Cai L, Qiu P, Deng X, Hu D, Zhang Q, Fan Y, Wu J, Wang L, Zhang M, Yu X, Zhai X, Tian K. The epidemic status and genetic diversity of 14 highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) isolates from China in 2009. Vet Microbiol. 2011;150:257–69. Xie J, Zhu W, Chen Y, Wei C, Zhou P, Zhang M, Huang Z, Sun L, Su S, Zhang G. Molecular epidemiology of PRRSV in South China from 2007 to 2011 based on the genetic analysis of ORF5. Microb Pathog. 2013;63:30–6. Tian K. NADC30-Like Porcine Reproductive and Respiratory Syndrome in China. Open Virol J. 2017;11:59–65. Bao H, Li X. Emergence and spread of NADC34-like PRRSV in China. Transbound Emerg Dis. 2021;68:3005–8. Wang X, Yang X, Zhou R, Zhou L, Ge X, Guo X, Yang H. Genomic characterization and pathogenicity of a strain of type 1 porcine reproductive and respiratory syndrome virus. Virus Res. 2016;225:40–9. Li B, Gao S, Zhou T, Liu X, Lu H, Feng F. Complete Genome Sequence of European Genotype Porcine Reproductive and Respiratory Syndrome Virus Strain LNEU12 in Northern China. Genome Announc, 2014. 2. Ming S, Yongying M, Bohua L, Huiying L, Xiaoyu D, Qiaorong L, Mingming Q, Xi C, Xinyan Y, Xizhao C. Pathogenic Characterization of European Genotype Porcine Reproductive and Respiratory Syndrome Virus Recently Isolated in Mainland China. Open Virol J. 2017;11:83–9. Nan Y, Wu C, Gu G, Sun W, Zhang YJ, Zhou EM. Improved Vaccine against PRRSV: Current Progress and Future Perspective. Front Microbiol. 2017;8:1635. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3012980","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":207249483,"identity":"6351e12b-127f-443d-b730-a1a1a28b89c6","order_by":0,"name":"Hang Zhang","email":"","orcid":"","institution":"Foshan University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Hang","middleName":"","lastName":"Zhang","suffix":""},{"id":207249484,"identity":"dc9d165e-c220-4a28-ad80-02839a310f48","order_by":1,"name":"Qin Luo","email":"","orcid":"","institution":"Foshan University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Qin","middleName":"","lastName":"Luo","suffix":""},{"id":207249485,"identity":"c243cba3-490d-4920-981d-455b563b7628","order_by":2,"name":"Yajie Zheng","email":"","orcid":"","institution":"Foshan University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yajie","middleName":"","lastName":"Zheng","suffix":""},{"id":207249486,"identity":"ca8c6f02-3a0b-42e0-b7b5-600072ffabff","order_by":3,"name":"Huiyang Sha","email":"","orcid":"","institution":"Foshan University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Huiyang","middleName":"","lastName":"Sha","suffix":""},{"id":207249487,"identity":"d8de47e5-5d9c-43cc-988a-1280cc5ae4f8","order_by":4,"name":"Gan Li","email":"","orcid":"","institution":"Foshan University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Gan","middleName":"","lastName":"Li","suffix":""},{"id":207249488,"identity":"c4b75188-da53-4100-986c-3049ee21079b","order_by":5,"name":"Weili Kong","email":"","orcid":"","institution":"University of California","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Weili","middleName":"","lastName":"Kong","suffix":""},{"id":207249489,"identity":"7be2fc6c-bdae-4694-95a5-abfd710a35ab","order_by":6,"name":"Liangzong Huang","email":"","orcid":"","institution":"Foshan University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Liangzong","middleName":"","lastName":"Huang","suffix":""},{"id":207249490,"identity":"728f07d3-d8d9-4a49-9d0b-2da46a38c106","order_by":7,"name":"Mengmeng Zhao","email":"data:image/png;base64,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","orcid":"","institution":"Foshan University","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Mengmeng","middleName":"","lastName":"Zhao","suffix":""}],"badges":[],"createdAt":"2023-06-02 06:44:32","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3012980/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3012980/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":38235706,"identity":"64f5b1cc-ff7b-4462-9c2e-b6a10c232dc8","added_by":"auto","created_at":"2023-06-08 15:12:33","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":756694,"visible":true,"origin":"","legend":"\u003cp\u003eResults of nucleotide homology in NSP2 sequence of 69 PRRSV-1 strains. Clustal W method in MegAlign function of DNAStar software was used to analyze the homology of NSP2 nucleotides. The red font displays the highest homology value, while the blue font displays the lowest homology value.\u003c/p\u003e","description":"","filename":"Fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-3012980/v1/040db828a6f9a8cc55d4828f.png"},{"id":38236713,"identity":"39849570-c942-43f1-beba-8fe4a14bc683","added_by":"auto","created_at":"2023-06-08 15:20:33","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":748152,"visible":true,"origin":"","legend":"\u003cp\u003eResults of amino acid homology in the NSP2 sequence of 69 PRRSV-1 strains. Cluster W method in MegAlign function of DNAStar software was used to analyze the homology of NSP2 amino acids. The red font displays the highest homology value, while the blue font displays the lowest homology value.\u003c/p\u003e","description":"","filename":"Fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-3012980/v1/696bc0b0b506e372e8ec17d6.png"},{"id":38235707,"identity":"bec088c1-bf77-45c4-8d73-9cad8e66a43a","added_by":"auto","created_at":"2023-06-08 15:12:33","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":13399626,"visible":true,"origin":"","legend":"\u003cp\u003eNSP2 amino acid sequence alignment results of representative strains of PRRSV. Using GENEDOC software (version 2.7), NSP2 amino acids were analyzed and divided into three levels based on amino acid similarity. A gray background indicates similarity between 75% and 100%, a yellow background indicates similarity between 50% and 75%, and a white background indicates similarity between 25% and 50%. The green area on the left represents PRRSV-1, and the blue area represents PRRSV-2. “.”represents amino acid homologous sites, “-” represents amino acid deletion sites. The content in the red box represents the missing site of the PRRSV-1 NSP2 amino acid.\u003c/p\u003e","description":"","filename":"Fig3.png","url":"https://assets-eu.researchsquare.com/files/rs-3012980/v1/e8b03e5d0ccd5384a86180d1.png"},{"id":38235704,"identity":"ee0efe9b-5829-400e-b34d-8f4c5bbd1976","added_by":"auto","created_at":"2023-06-08 15:12:33","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":824064,"visible":true,"origin":"","legend":"\u003cp\u003ePhylogenetic analysis based on the PRRSV \u003cem\u003eNSP2\u003c/em\u003egene. 69 PRRSV-1 strains and 21 PRRSV-2 strains were selected for NSP2 sequences, and a NJ phylogenetic tree was constructed using MEGA software (version 7.0), and 1000 bootstrap replications were performed. The red background refers to the PRRSV-2 strains, while the blue background refers to the PRRSV-1 strains. Triangle (▲) refers to the Chinese PRRSV-1 strains, while square (■) refers to the PRRSV-1 vaccine strains.\u003c/p\u003e","description":"","filename":"NJ1.png","url":"https://assets-eu.researchsquare.com/files/rs-3012980/v1/5677d0ee6e4fba4ee9b37826.png"},{"id":38237062,"identity":"edd1f44f-ceeb-4347-b458-97d9cad3e680","added_by":"auto","created_at":"2023-06-08 15:28:33","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":689059,"visible":true,"origin":"","legend":"\u003cp\u003ePhylogenetic analysis based on the PRRSV \u003cem\u003eNSP2\u003c/em\u003egene. 69 PRRSV-1 strains and 21 PRRSV-2 strains were selected for NSP2 sequences, and a ML phylogenetic tree was constructed using PhyloSuite software (version 1.2.2), and 1000 bootstrap replications were performed. The red background refers to the PRRSV-2 strains, while the blue background refers to the PRRSV-1 strains. Triangle (▲) refers to the Chinese PRRSV-1 strains, while square (■) refers to the PRRSV-1 vaccine strains.\u003c/p\u003e","description":"","filename":"CfjuMZoN9k0XolqsB8UAQw.png","url":"https://assets-eu.researchsquare.com/files/rs-3012980/v1/11f200273493add75e1fb43e.png"},{"id":38235705,"identity":"c087c5e5-0cd5-48f6-849b-5faffbf15f51","added_by":"auto","created_at":"2023-06-08 15:12:33","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":524634,"visible":true,"origin":"","legend":"\u003cp\u003eRDP (version 4.0) verification of \u003cem\u003eNSP2\u003c/em\u003e gene recombination events. The horizontal axis represents position in alignment, and the vertical axis represents pairwise identity. (a) is the RDP analysis result of the recombinant strain HU18755-2016; (b) is the RDP analysis result of the recombinant strain NVDC-NM1-2011; (c) is the RDP analysis result of the recombinant strain 13V091-2013; (d) is the RDP analysis result of the recombinant strain HKEU16-2007.\u003c/p\u003e","description":"","filename":"Fig6.png","url":"https://assets-eu.researchsquare.com/files/rs-3012980/v1/b0e513c8904f3a249834a116.png"},{"id":38236712,"identity":"af853ac4-6b2d-4095-a13a-93f30e4377b2","added_by":"auto","created_at":"2023-06-08 15:20:33","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":609198,"visible":true,"origin":"","legend":"\u003cp\u003eSimple (version 3.5.1) verification of \u003cem\u003eNSP2\u003c/em\u003e gene recombination events. The horizontal axis represents position, and the vertical axis represents percentage of permuted trees. (a) is the Simplot validation result of the recombinant strain HU18755-2016; (b) is the Simplot validation result of the recombinant strain NVDC-NM1-2011; (c) is the result of Simplot validation of the recombinant strain 13V091-2013; (d) is the result of Simplot validation of the recombinant strain HKEU16-2007.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-3012980/v1/face1a4fb82f16b2f91002b6.png"},{"id":40223809,"identity":"86575c9b-619f-458c-93d3-d95f8975a41c","added_by":"auto","created_at":"2023-07-19 01:14:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3899996,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3012980/v1/adb50bad-25b5-4b94-99ba-effe66fe7f73.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Genetic Variability and Recombination of the NSP2 Gene of PRRSV-1 Strains in China from 1996 to 2022","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003ePorcine reproductive and respiratory syndrome (PRRS) is a highly contagious disease caused by the porcine reproductive and respiratory syndrome virus (PRRSV). Since its first report in 1987, PRRS has resulted in significant economic losses of up to \u003cspan\u003e$\u003c/span\u003e600\u0026nbsp;million per year in the United States (approximately \u003cspan\u003e$\u003c/span\u003e1.8\u0026nbsp;million per day). In China the losses have been even higher, primarily due to secondary infections from other diseases such as swine fever, pseudorabies, and bacterial diseases like porcine infectious pleuropneumonia [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. In 1991 and 1992, two strains of Lelystad virus and VR2332 were isolated from infected pigs in Europe and America, respectively. These strains were classified into two genotypes, PRRSV-1 and PRRSV-2, based on their antigenic differences [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. PRRSV-1 and PRRSV-2 are currently classified as two species, Betaarterivirus suid 1 and Betaarterrus suid 2, respectively. The first isolation of type 2 PRRSV was in Harbin, China in 1996 and it was named CH-1a. The entire genome sequence of Ch-1a was uploaded to GenBank in the same year with login number AY032626 [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Type 1 PRRSV, also known as B13, was initially discovered in Beijing, China in 1997. However, only its ORF5 gene was uploaded to GenBank in 2004 with the login number AY633973 [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Currently, PRRSV-2 is predominantly found in North America and Asia, with PRRSV-1 also being present. South America only has PRRSV-2, while Europe mostly relies on PRRSV-1. However, PRRSV-2 is also found in Western Europe. PRRSV has not yet been reported in Australia. As of 2022, the occurrence and prevalence of PRRS globally has remained stable.\u003c/p\u003e \u003cp\u003ePRRSV is a single-stranded positive-sense RNA virus with a capsule. Its genome consists of 11 open reading frames (ORFs) and has a length of 15 kb and, namely ORF1a, ORF1b, ORF2a, ORF2b, ORF3-7, ORF5a, and ORF1aTF, that overlaps the non-structural protein (NSP)2-coding region of ORF1a [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Among them, ORF1a and ORF1aTF translationally encode at least 12 NSPs, including NSP1α, NSP1β, NSP2 and its related proteins (NSP2N and NSP2TF), NSP3, NSP4, NSP5, NSP6, NSP7α, NSP7β and NSP8; NSP2 at 2.9 kb in length is the longest [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. NSP2 and ORF5 are highly variable and ORF5 is associated with the neutralizing epitope. They are usually used as target genes for PRRSV molecular epidemiology surveillance [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. PRRSV NSP2 is not only associated with the genetic variation but also plays a role in multiple biological processes as a multifunctional protein. A comprehensive understanding of NSP2 can greatly contribute to the elucidation of the pathogenesis of this disease.\u003c/p\u003e \u003cp\u003eIn their study, Shi et al. conducted a phylogenetic analysis on ORF5 sequences available in GenBank and identified three subtypes of PRRSV-1: Subtype I (Global, Russian), Subtype II (Russian, Lithuania, Belarus), and Subtype III [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Subtype I of PRRSV-1 was initially detected in several countries in Western Europe and has since spread to Asia and the Americas. It has 12 evolutionary branches. On the other hand, Subtype II and Subtype III are mainly found in Eastern Europe and Russia. In China, the majority of PRRSV-1 isolates are Subtype I Global. In 2017, Chen et al. classified PRRSV-1 into four gene subgroups in China, namely Amervac-like, BJEU06-1-like, HKEU-16-like, and NMEU09-1-like [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Due to the prevalence of PRRSV-2 in China, most research on NSP2 has focused on this strain. However, there has been an increase in the occurrence of PRRSV-1 in recent years, indicating a need for further investigation into NSP2 and its role in this strain as well [\u003cspan additionalcitationids=\"CR13\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. This study aims to understand the genetic variation of NSP2 protein in the classic strain NSP2 of PRRSV-1. It does this by comparing the nucleotide and amino acid homology, conducting multiple sequence alignment of amino acids, analyzing the phylogenetic relationship of \u003cem\u003eNSP2\u003c/em\u003e gene, and finally conducting recombination analysis. The findings of this study can help in timely monitoring of the future epidemic trend of PRRSV-1.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e"},{"header":"2 Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 The Dataset\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eA total of 25 Chinese PRRSV-1 strains (including Amervac-like, BJEU06-1-like, HKEU-16-like, and NMEU09-1-like gene subgroups), 44 foreign PRRSV-1 strains, and 21 PRRSV-2 strains (including lineages 1, 3, 5, and 8) were carefully selected from the GenBank database of the NCBI website (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The selection criteria were based on the inclusion of strains from different years ranging from 1996 to the present, representation of commonly reported PRRSV strains in literature, and the inclusion of commonly used PRRSV-1 vaccine strains.The Dataset\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Nucleotide homology analysis of PRRSV-1 NSP2\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eTo determine the homology between nucleotide sequences of PRRSV-1 NSP2, this study analyzed 69 PRRSV-1 strain NSP2 sequences using the Cluster W method in the MegAlign function of DNAStar software (version 7.0, Madison, WI). The resulting analysis was presented using Sequence Distances.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Amino acid homology analysis of PRRSV-1 NSP2\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eTo determine the homology between the amino acid sequences of PRRSV-1 NSP2, we translated the above 69 strains of nucleotides into amino acid sequences. The amino acid sequences were analyzed using the Cluster W method in the MegAlign function of DNAStar software (version 7.0, Madison, WI), and the analysis results were displayed using Sequence Distances.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Alignment of PRRSV-1 NSP2 Amino Acid Sequences\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eIn order to compare the differences in NSP2 amino acid sites between PRRSV-1 and PRRSV-2, this study utilized 34 PRRSV-1 and six PRRSV-2 NSP2 sequences from Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e for multiple sequence alignment. The sequences were imported into GENEDOC software (version 2.7) for amino acid sequence alignment.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Phylogenetic Analysis\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe \u003cem\u003eNSP2\u003c/em\u003e gene phylogenetic analysis was conducted using the sequence information of 90 PRRSV strains as presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The analysis involved the Cluster W method in the MegAlign function of DNAStar software (version 7.0, Madison, WI), followed by 1000 boot repetitions using the Neighbor Connection (NJ) method of MEGA software (version 7.0.26, Mega Limited, Auckland, New Zealand). Further analysis was conducted using the maximum likelihood (ML) method of PhyloSuite software (version 1.2.2) with 1000 bootstrap repetitions. The resulting phylogenetic tree was annotated using the online software The Interactive Tree Of Life (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://itol.embl.de\u003c/span\u003e\u003cspan address=\"https://itol.embl.de\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.6 Recombination Analysis\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eTo perform recombination analysis, import the processed sequences into RDP (version 4.0) software and use seven methods (RDP, MaxChi, GeneConv, BootScan, SiScan, 3Seq, and Chimaera) with default settings. Only recombination events confirmed by at least 5 of the 7 methods and a p-value threshold of 0.05 are reported. The identified strain is considered a recombinant strain. Additionally, SimPlot (version 3.5.1) was used to confirm the detected recombination events.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe reference sequence of PRRSV NSP2 strains.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYear\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAera\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003esequence\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eStrain\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eGenbank Accession number\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eType\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHK3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKF287129\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHK5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKF287130\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHK8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKF287128\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHK10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKF287131\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBJEU06-1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eGU047344\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2007\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHKEU16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eEU076704\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2009\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSHE\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eGQ461593\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2009\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNMEU09-1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eGU047345\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGZ11-G1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKF001144\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNVDC-FJ\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKC492506\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNVDC-NM1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eJX187609\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNVDC-NM2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKC492504\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNVDC-NM3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKC492505\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2012\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLNEU12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKM196101\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFJEU13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKP860912\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2014\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFJQEU14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKP860913\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2014\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHLJB1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKT224385\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e15HEN1_EU\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKX967492\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2017\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHENZMD-10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKY363382\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2018\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eKZ2018\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMN550991\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2018\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eEUGDHD2018\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMK639926\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2018\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNPUST-2789-3W-2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMN242825\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2020\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSC-2020-1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMW115431\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2020\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTZJ226\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eOP566682\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2020\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTZJ637\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eOP566683\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1991\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNetherlands\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLelystad virus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eM96262\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1992\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBelgium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBE_92V058\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMW448197\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1996\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBelgium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e96V198\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMK876228\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1999\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNetherlands\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMLV-DV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKJ127878\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUSA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSD-01-08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eDQ489311\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUSA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eEuroPRRSV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eAY366525\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBelgium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBE_03V140\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMW053394\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNetherlands\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePRRSV LV4.2.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eAY588319\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnited Kingdom\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e215-06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eOP047897\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2007\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBelarus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLena\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eJF802085\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2008\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBelgium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBE_08V156\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMW053397\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2008\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBelarus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003elena\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eJF802085\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2009\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpain\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAmervac PRRS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eGU067771\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBelarus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSU1-Bel\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKP889243\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSouth Korea\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eD40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMZ287330\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2012\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGermany\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGER12-720789\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eOP529852\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRussia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eWestSib13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKX668221\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBelgium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e13V117\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKT159249\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBelgium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBE_13V246\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMW053396\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBelgium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBE_13V173\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMW053395\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBelgium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e13V091\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKT159248\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBelgium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBE_13V200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMW053399\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBelgium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBE_13V153\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMW053398\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpain\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eES13-49_P85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMK024325\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBelgium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBE_13V264\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMW053400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2014\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGermany\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDE14-3073_P85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMK024324\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2014\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDenmark\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePorcilis_DV-MLV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMT311646\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2014\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBelgium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBE_14V023\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMW053401\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2014\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePoland\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePL14-02_P85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMK024327\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2014\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eItaly\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePR40/2014\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMF346695\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2014\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eItaly\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eIT14-32_P85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMK024326\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSouth Korea\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eJB15-E-M17-JB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMZ287329\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSouth Korea\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eJB15-E-P47-GB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMZ287328\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSouth Korea\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCBNU0495\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMZ287327\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFrance\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePRRS-FR-2016-56-11-1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMH018883\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHungary\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHU19401/2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMH463457\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHungary\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHU24924/2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMH463459\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHungary\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHU19483/2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMH463458\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHungary\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHU18861/2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMH463456\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHungary\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHU18755/2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMH463455\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRussia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTyu16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMT008024\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2019\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSouth Korea\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eJBNU-19-E01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMW847781\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2019\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDenmark\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDK-2019-10166-107\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMN603982\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2022\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAustria\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAUT22-97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eOP627116\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1992\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUSA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eVR2332\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eEF536003.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1996\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBJ-4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eAF331831\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHN1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eAY457635.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2008\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePRRSV01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eFJ175687\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2009\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSD1-100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eGQ914997\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2012\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHZ-31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKC445138\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1996\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCH-1a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eAY032626\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTJ\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eEU860248\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHUB1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eEF075945\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eJXA1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eEF112445\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHUN4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eEF635006.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eQY2010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eJQ743666\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGM2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eJN662424\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eQYYZ\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eJQ308798\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2012\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFJFS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKP998476\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGDsg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKX621003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eJL580\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKR706343.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFJW05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKP860911\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHNjZ15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKT945017\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFJZ03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eKP860909\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2017\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNSP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNADC30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMH500776.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePRRSV-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"3 Results","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Nucleotide Similarity\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThis study aimed to investigate the genetic variation of \u003cem\u003eNSP2\u003c/em\u003e gene in PRRSV-1 by analyzing 25 Chinese PRRSV-1 and 44 foreign PRRSV-1 NSP2 sequences for nucleotide homology. The results indicated that the nucleotide similarity of PRRSV-1 NSP2 ranged from 42.1\u0026ndash;97.0% (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The highest similarity was found between Amervac PRRS-2009 and SHE-2009, at 97.0%, while the lowest similarity was observed between BE_14V023-2014 and Tyu16-2016, at 42.1%.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Amino Acid Sequence Similarity\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eAfter comparing the nucleotide similarity of PRRSV-1 NSP2, we translated the nucleotide sequences of 69 NSP2 strains into amino acids for homology analysis. The results indicated that the amino acid similarity of PRRSV-1 NSP2 ranged from 59.4\u0026ndash;100.0% (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The highest similarity was found between BE_08V156-2008 and Lena-2007, BE_08V156-2008 and lena-2008, as well as Lena-2007 and lena-2008, at 100.0%, while the lowest similarity was observed between PR40-2014 and WestSib13-2013, at 59.4%.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Amino Acid Sequence Alignment\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eTo compare the variation in NSP2 amino acid sequences between PRRSV-1 and PRRSV-2, this study selected 34 PRRSV-1 and six PRRSV-2 NSP2 sequences for multiple sequence alignment. The results showed that PRRSV-1 NSP2 amino acids had more missing sites compared to PRRSV-2 (as indicated by the red box in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), and the similarity of PRRSV-1 NSP2 was lower. The missing sites were mainly concentrated at positions 30\u0026ndash;40, 150\u0026ndash;153, 190\u0026ndash;200, 215\u0026ndash;220, 240\u0026ndash;250, 510\u0026ndash;520, 530\u0026ndash;580, 620\u0026ndash;623, and 790\u0026ndash;820 amino acids. The regions with higher mutation rates were mainly concentrated at positions 10\u0026ndash;30, 300\u0026ndash;410, 420\u0026ndash;480, 750\u0026ndash;780, and 820\u0026ndash;850 amino acids. The variation of NSP2 between PRRSV-1 showed no regularity, with the most significant loss of NSP2 at sites 288\u0026ndash;463.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Phylogenetic Analysis\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eTo demonstrate the phylogenetic relationship of the PRRSV-1 \u003cem\u003eNSP2\u003c/em\u003e gene, this study analyzed NSP2 sequences of 90 PRRSVs using the NJ method of MEGA software (version 7.0) and the ML method of PhyloSuite software (version 1.2.2) to construct a phylogenetic tree. The results indicate that PRRSV-1 and PRRSV-2 belong to two different evolutionary branches (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e and \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Additionally, the genetic relationships between BJEU06-1-like and NMEU09-1-like in PRRSV-1 are closer, while the genetic relationships with Amervac-like and HKEU-16-like are farther. The vaccine strains Amervac PRRS-2009 and SHE-2009 show relatively close genetic relationships in both algorithms. Similarly, the vaccine strains MLV-DV-1999 and Porcilis_DV-MLV-2014 show a relatively close genetic distance to the European representative Lelystad virus.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Recombinant Analysis\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThis study aimed to gain a better understanding of the genetic evolution of the PRRSV-1 \u003cem\u003eNSP2\u003c/em\u003e gene, through recombination analysis of the NSP2 sequences of 90 collected PRRSV strains. The analysis, conducted using RDP (version 4.0), revealed a total of four potential recombination events in the NSP2 sequence of the 90 PRRSV strains. All four recombination events were supported by more than five algorithms, indicating high reliability and statistical significance (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The results of the analysis are presented in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. In event 1, the primary and secondary parental strains of the recombinant strain HU18755-2016 are JB15-E-P47-GB-2015 and HU18861-2016, respectively; In event 2, the primary and secondary parental strains of the recombinant strain NVDC-NM1-2011 are HENZMD-10 2017 and BJEU06-1 2006, respectively; In event 3, the primary and secondary parent strains of the recombinant strain 13V091-2013 are NMEU09-1-2009 and HU18861-2016, respectively; In event 4, the primary and secondary parent strains of the recombinant strain HKEU16-2007 are HK5-2004 and HK10-2004, respectively. To verify the four recombination events obtained, we used Simplot (version 3.5.1) and the results showed that all four potential recombination events are valid (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). Out of these four recombinant events, only NVDC-NM1-2011 and HKEU16-2007 are PRRSVs from China, while HU18755-2016 and 13V091-2013 are PRRSVs from other countries.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eRecombination analysis of \u003cem\u003eNSP2\u003c/em\u003e gene.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRecombination event\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRecombinant strains\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMain parental strain\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMinor parental strain\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eRecombinant breakpoint\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eRecombination analysis method\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHU18755-2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eJB15-E-P47-GB-2015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHU18861-2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e35\u0026thinsp;~\u0026thinsp;2567 (667\u0026thinsp;~\u0026thinsp;837)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eRDP(P\u0026thinsp;=\u0026thinsp;1.517\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;22\u003c/sup\u003e) GENECONV(P\u0026thinsp;=\u0026thinsp;1.203\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;25\u003c/sup\u003e) BootScan(P\u0026thinsp;=\u0026thinsp;1.290\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;26\u003c/sup\u003e) MaxChi(P\u0026thinsp;=\u0026thinsp;2.041\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;13\u003c/sup\u003e) Chimaera(P\u0026thinsp;=\u0026thinsp;3.549\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;9\u003c/sup\u003e) SiScan(P\u0026thinsp;=\u0026thinsp;8.274\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;25\u003c/sup\u003e) 3seq (P\u0026thinsp;=\u0026thinsp;1.583\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNVDC-NM1-2011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eHENZMD-10-2017\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBJEU06-1-2006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e35\u0026thinsp;~\u0026thinsp;2504 (1142\u0026thinsp;~\u0026thinsp;1212)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eRDP(P\u0026thinsp;=\u0026thinsp;5.108\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;20\u003c/sup\u003e) GENECONV(P\u0026thinsp;=\u0026thinsp;9.576\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;18\u003c/sup\u003e) BootScan(P\u0026thinsp;=\u0026thinsp;1.451\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;28\u003c/sup\u003e) MaxChi(P\u0026thinsp;=\u0026thinsp;6.927\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;18\u003c/sup\u003e) Chimaera(NS) SiScan(P\u0026thinsp;=\u0026thinsp;1.591\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;36\u003c/sup\u003e) 3seq (P\u0026thinsp;=\u0026thinsp;2.136\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13V091-2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNMEU09-1-2009\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHU18861-2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1449\u0026thinsp;~\u0026thinsp;1615 (947\u0026thinsp;~\u0026thinsp;2050)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eRDP(P\u0026thinsp;=\u0026thinsp;3.072\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e) GENECONV(NS) BootScan(P\u0026thinsp;=\u0026thinsp;2.299\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e) MaxChi(P\u0026thinsp;=\u0026thinsp;4.189\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e) Chimaera(1.268\u0026times;10\u0026thinsp;\u0026minus;\u0026thinsp;4) SiScan(P\u0026thinsp;=\u0026thinsp;1.043\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e) 3seq (P\u0026thinsp;=\u0026thinsp;2.846\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHKEU16-2007\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eHK5-2004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHK10-2004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e954\u0026thinsp;~\u0026thinsp;1062 (1206\u0026thinsp;~\u0026thinsp;1406)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eRDP(NS) GENECONV(P\u0026thinsp;=\u0026thinsp;1.797\u0026times;10\u0026thinsp;\u0026minus;\u0026thinsp;2) BootScan(P\u0026thinsp;=\u0026thinsp;2.727\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e) MaxChi(P\u0026thinsp;=\u0026thinsp;1.748\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e) Chimaera(1.337\u0026times;10\u0026thinsp;\u0026minus;\u0026thinsp;2) SiScan(P\u0026thinsp;=\u0026thinsp;4.185\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e) 3seq (P\u0026thinsp;=\u0026thinsp;2.443\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4 Discussion","content":"\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003ePRRS is a significant infectious diseases that affects the global pig industry due to the susceptibility of PRRSV genome to mutation, which can lead to immune escape [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. The main epidemic strain in China is PRRSV-2, and current domestic vaccines mainly target this strain. Therefore, most research focuses on PRRSV-2. However, the detection rate of PRRSV-1 has been increasing in different regions of China in recent years. Multiple regions, such as 22 provinces including Fujian, Zhejiang, Guizhou, Hong Kong, Liaoning, Heilongjiang, and Henan, have reported the detection of PRRSV-1 [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Monitoring the epidemic trend of PRRSV-1 is crucial for preventing and controlling its occurrence. NSP2, the most mutated non-structural protein in PRRSV, plays a vital role in virus replication, transcription, and regulation of host immune response by interacting with host proteins. [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The \u003cem\u003eNSP2\u003c/em\u003e gene exhibits multiple mutation modes, including deletion, recombination, and insertion leading to significant differences in the size of \u003cem\u003eNSP2\u003c/em\u003e gene fragments [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Due to this, NSP2 is often used as a target gene for analyzing genetic variation and evolution of PRRSV.\u003c/p\u003e \u003cp\u003eIn this study, only a limited number of Chinese PRRSV-1 sequences were available from NCBI, some of which only had ORF5 sequences. Therefore, we collected a total of 25 Chinese PRRSV-1 NSP2 sequences to better understand the differences between PRRSV-1 in China and foreign countries. To expand our analysis, we also selected 44 NSP2 sequences of PRRSV-1 isolated from abroad, resulting in a total of 69 PRRSV-1 sequences analyzed for nucleotide and amino acid homology. The results showed that the nucleotide and amino acid homology ranged from 42.1\u0026ndash;97.0% and 59.4\u0026ndash;100.0%, respectively. In comparison, the nucleotide and amino acid homology of PRRSV-2 NSP2 reported by Zhang et al. were 72.5\u0026ndash;99.8% and 63.9\u0026ndash;99.4%, respectively [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. The study reveals that PRRSV-1 NSP2 has lower nucleotide and amino acid homology than PRRSV-2, indicating a higher tendency for mutation. To understand the differences in NSP2 amino acid sites between PRRSV-1 and PRRSV-2, the study conducted multiple sequence alignments of 34 and six PRRSV-2 NSP2 sequences, respectively. The results suggest that PRRSV-1 NSP2 has more deletions and replacement sites compared to PRRSV-2. Furthermore, the deletion sites of PRRSV-1 NSP2 are more irregular, which poses a significant challenge for PRRSV-1 vaccine research. In 2020, Zhang et al. discovered a 6 aa deletion (aa357-360\u0026thinsp;+\u0026thinsp;aa411\u0026thinsp;+\u0026thinsp;aa449) in the NSP2 region of a PRRSV-1 strain named KZ2018 [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. This study dentified that 13V091-2013, BE_13V153-2013, and HU18755-2016 have the same deletion pattern in the NSP2 region, which can serve as a reference for \u003cem\u003eNSP2\u003c/em\u003e gene classification in PRRSV-1. The NSP2 sequences of 90 PRRSV strains were then subjected to phylogenetic analysis using the NJ and ML methods of MEGA (version 7.0) and Simplot (version 3.5.1) software. The analysis revealed that PRRSV-1 contains closely related BJEU06-1-like and NMEU09-1-like viruses, which are located in the same evolutionary branch. However, Amervac-like and HKEU-16-like strains were found to be genetically distant from them. The genetic relationship between BJEU06-1-like and NMEU09-1-like was relatively close based on the phylogenetic tree of the ORF5 gene reported by Li et al., although they were not in the same branch. Similarity, the genetic relationship between HKEU-16-like and NMEU09-1-like was also relatively close. However, the whole genome-based phylogenetic trees showed different results, with BJEU06-1-like having a closer genetic relationship with HKEU-16-like, and Amervac-like having a closer genetic relationship with NMEU09-1-like [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The reason for this difference may be that there is a notable variation in the PRRSV-1 \u003cem\u003eNSP2\u003c/em\u003e gene, but despite this difference, each strain falls under the same branch as the ORF5 based whole genome sequence. As a result, the findings of this research can serve as a valuable point of reference for the categorization of PRRSV-1 based on the \u003cem\u003eNSP2\u003c/em\u003e gene. This study analyzed 90 PRRSV-1 NSP2 sequences and identified four potential recombination events, of which only two were found in China. Both recombination strains had Chinese parent strains. No recombination was detected between vaccine and wild strains in this study. However, it is worth noting that in a previous study by Chen et al. in 2022, [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e] the HLJB1 isolate was found to be the result of recombination between the Amervac vaccine strain and the BJEU06-1 strain. This discrepancy may be due to the fact that Chen et al. analyzed the full-length sequence for recombination, while this study focused only on NSP2 sequence.\u003c/p\u003e \u003cp\u003ePRRSV is known for its high mutation rate, particularly in the ORF5 gene, which makes it prone to recombination or mutation events. In contrast, the NSP4 gene is relatively conservative [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], while NSP2, like ORF5, shows high variability, as confirmed by the results of this study. PRRSV-2 and PRRSV-1 were first reported in China in 1996 and 1997, respectively [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Despite the one-year difference, there has been a significant disparity in the prevalence of the two types of PRRSVs over the past 20 years. PRRSV-2 has undergone several highly pathogenic PRRS outbreaks [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], including lineage 3 represented by QYYZ [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e], NADC30 like [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e], and the current NADC34 outbreak [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. PRRSV-1 has always been endemic and sporadic, spreading throughout central, northern, southern, eastern, northeastern, and southwestern regions of China [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. The virulence of PRRSV-2 has evolved from low to high pathogenicity, while the virulence of PRRSV-1 is relatively mild, mainly manifested in reproductive disorders in sows and some cases of fever and respiratory difficulties [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. In China, vaccination is an important method for preventing and controlling PRRS. Domestic vaccines primarily target PRRSV-2 [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e], while vaccines targeting PRRSV-1 include Porcilis PRRS (Merck), UNISTRAIN PRRS (Hipra), Ingelvac PRRSFLEX EU (Boehringer Ingelheim), ReproCyc PRRS EU (Boehringer Ingelheim), and Suvaxyn PRRS MLV (Zoetis) from abroad. The use of attenuated live vaccines not only poses a risk of returning to strong virulence, but may also cause recombination with wild strains, making prevention and control more difficult. Despite over 20 years of research, PRRSV remains a mystery and a successful prevention and eradication strategy has yet to be found. Although there is a deep understanding of the clinical pathogenesis, molecular epidemiology, virus proliferation, pathogenesis, immune response, and immune escape mechanism of PRRSV, timely monitoring of genetic variations in PRRSV can serve as a reference for effective control of PRRS in China in the future.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e"},{"header":"5 Conclusions","content":"\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eBetween 1996 and 2022, PRRSV-1 isolates in China have been classified into four gene subgroups: Amervac like, BJEU06-1-like, HKEU-16-like, and NMEU09-1-like. Studies have shown that the NSP2 sequence of PRRSV-1 displays more variation, deletion, and replacement regions compared to PRRSV-2. However, the recombination rate of the NSP2 region of PRRSV-1 is lower than that of PRRSV-2.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor Contributions:\u003c/strong\u003e Writing\u0026mdash;original draft preparation, H.Z. and Q.L.; writing\u0026mdash;review and editing, Y.Z. and H.S.; software, G.L.; methodology, W.K.; funding acquisition, L.H.; visualization, M.Z. All authors have read and agreed to the published version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u0026nbsp;\u003c/strong\u003eThis research was funded by National Natural Science Foundation of China (31902279).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInstitutional Review Board Statement:\u003c/strong\u003e Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInformed Consent Statement:\u0026nbsp;\u003c/strong\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability Statement:\u003c/strong\u003e All datasets are available in the main manuscript. The dataset supporting the conclusions of this article is included within the article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of Interest:\u0026nbsp;\u003c/strong\u003eThe authors declare no conflict of interest.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBrashishkite DA, Galetsky SA, Kuliffay P, Lizonova A, Tatosyan AG, Urbancikova M, Kisselyov FL, Grofova M. BrdU-induced changes in the provirus of PR-RSV in mammalian cells. Neoplasma. 1988;35:643\u0026ndash;50.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWensvoort G, Terpstra C, Pol JM, ter Laak EA, Bloemraad M, de Kluyver EP, Kragten C, van Buiten L, den Besten A, Wagenaar F, et al. Mystery swine disease in The Netherlands: the isolation of Lelystad virus. 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Front Microbiol. 2017;8:1635.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Genetic variability, recombination, PRRSV-1, NSP2 gene, China","lastPublishedDoi":"10.21203/rs.3.rs-3012980/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3012980/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePorcine reproductive and respiratory syndrome (PRRS) has been present in China for over 20 years. Due to the continuous mutation of PRRS virus (PRRSV), it causes significant economic losses to the pig industry annually. This study aimed to understand the genetic variation of the PRRSV-1 \u003cem\u003eNSP2\u003c/em\u003e gene in China. A total of 69 PRRSV-1 NSP2 strains, consisting of 25 Chinese and 44 foreign strains, were collected and their nucleotide and amino acid homology were analyzed. Results indicated that the nucleotide homology of NSP2 ranged 42.1\u0026ndash;97.0%, while the amino acid homology ranged from 59.4\u0026ndash;100.0%. Multiple sequence alignments of NSP2 amino acids from the 69 PRRSV-1 strains were conducted to compare differential sites of NSP2 amino acids between PRRSV-1 and PRRSV-2. The study revealed that PRRSV-1 had more missing and replaced sites compared to PRRSV-2. A phylogenetic analysis of the NSP2 sequence of 90 PRRSV strains revealed that the genetic relationships between BJEU06-1-like and NMEU09-1-like are relatively close, but far from Amervac-like and HKEU-16-like. Additionally, recombinant analysis showed that four recombination events occurred in the 90 selected PRRSVs, with two occurring in the Chinese PRRSV-1 NSP2 sequence. These findings provide a deeper understanding of the prevalence of PRRSV-1 in China over the past 20 years and will serve as a theoretical basis for the evolution and epidemiology of PRRSV.The abstract serves both as a general introduction to the topic and as a brief, non-technical summary of the main results and their implications. Authors are advised to check the author instructions for the journal they are submitting to for word limits and if structural elements like subheadings, citations, or equations are permitted.\u003c/p\u003e","manuscriptTitle":"Genetic Variability and Recombination of the NSP2 Gene of PRRSV-1 Strains in China from 1996 to 2022","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-06-08 15:12:28","doi":"10.21203/rs.3.rs-3012980/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"09b3c416-fa67-49e1-a790-7103650463fe","owner":[],"postedDate":"June 8th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2023-07-19T01:14:13+00:00","versionOfRecord":[],"versionCreatedAt":"2023-06-08 15:12:28","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3012980","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3012980","identity":"rs-3012980","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}