Characterization of maternally derived antibody titers against porcine circovirus type 2 in serum of piglets and identification of piglets at elevated risk of infection

Characterization of maternally derived antibody titers against porcine circovirus type 2 in serum of piglets and identification of piglets at elevated risk of infection | 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 Characterization of maternally derived antibody titers against porcine circovirus type 2 in serum of piglets and identification of piglets at elevated risk of infection Makoto Ukita, Yukine Kano, Saya Taharaguchi, Tadashi Takino, Kohei Makita, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4182328/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 Background Porcine circovirus type 2 (PCV2) is commonly associated with several clinical syndromes and diseases collectively referred to as porcine circovirus-associated disease, which has a significant economic impact on the global swine industry. In Japan, PCV2 is endemic to most pig farms, and vaccination for piglets and/or sows has been implemented on most farms. The present study explored factors associated with piglets at elevated risk of PCV2 infection. Pre-vaccination serum samples were collected, from birth through 19 days, from 39 piglets born to five sows; these specimens were used to measure the titer of maternally derived antibody (MDA) against PCV2, immunoglobulin G concentration, and total protein concentration. Additionally, records of sow parity and piglet body weights were examined. Results Regarding anti-PCV2 MDA, the mean maximum sample-to-positive (S/P) ratios among litters born from the five sows differed significantly (p < 0.001). The half-life of the anti-PCV2 MDA was estimated to be 17.4 days (95% confidence interval: 16.2–18.9 days). The trend to lower antibody titers appeared to be attenuated in piglets born from sows with higher parities. Furthermore, among litters from sows with a large number of parities, litters with larger mean birth weights exhibited greater variability in antibody titers. Additionally, within litters of piglets with higher mean birth weights, piglets with lower birth weights or lower serum total protein concentrations exhibited lower antibody titers. Conclusions The present study aimed to evaluate the relationship between serum anti-PCV2 MDA titers and several indicators in suckling piglets and to identify characteristics of piglets at elevated risk of PCV2 infection. In the field, indicators such as sow parity, birth weight, and serum total protein concentration may facilitate the identification of piglets at elevated risk of PCV2 infection. Figures Figure 1 Figure 2 Background Porcine circovirus type 2 (PCV2) is commonly associated with several clinical syndromes and diseases collectively referred to as porcine circovirus-associated disease (PCVAD) [ 1 ], in weaned 5 to 12 weeks of age [ 2 ], which has a significant economic impact on the global swine industry [ 3 ]. PCV2 is a member of the genus Circovirus , of the family Circoviridae , the smallest non-enveloped, single-stranded, circular DNA virus that replicates autonomously in mammalian cells. PCV2 is currently classified into eight genotypes, labeled as PCV2a to PCV2h [ 4 , 5 ]. Until 2007, PCVAD outbreaks across the globe were associated primarily with PCV2b; the subsequent development and implementation of an anti-PCV2 vaccine based on a PCV2a antigen led to a reduction in the number of cases [ 6 , 7 ]. However, in 2012, PCVAD cases caused by PCV2d were reported in North America on farms employing the PCV2a-based vaccine [ 8 ]. More recently, PCV2d-2 has emerged as the predominant genotype worldwide. In Japan, the prevalence of anti-PCV2 antibody positivity in pig farms exceeds 90%, and most farms have implemented vaccination for 3-week-old piglets and/or sows three weeks before farrowing. On farms that vaccinate only piglets, the titer of anti-PCV2 antibodies in breeding sows depends on the natural infection of these animals, meaning that sows exhibit a wide range of antibody titers. Similarly, the maternally derived antibody (MDA) titers among the offspring of these sows exhibit large variations. Piglets with low MDA titers can be infected before vaccination. In previous studies, tracking the anti-PCV2 antibody titers of piglets at three weeks (pre-vaccination) and older (post-vaccination) revealed that the immune response was based on the level of antibody titers at the time of vaccination in experimental and field-level studies [ 9 , 10 ]. However, few studies have tracked anti-PCV2 MDA in serum from immediately after birth through vaccination and evaluated antibody titer dynamics and factors affecting these dynamics at the individual level. On Japanese farms, piglets typically are moved to weaning pig pens at three weeks of age and raised in herds. Any piglet that is infected with PCV2 prior to that move has the potential to serve as a source for the spread of infection to the herd. Therefore, it is crucial to identify piglets at high risk of infection in the field, especially those that lack sufficient pre-vaccination anti-PCV2 antibody titers at three weeks of age, which would increase the likelihood of infection. In the present study, pre-vaccination titers of anti-PCV2 antibodies in the serum of piglets were measured repeatedly from birth to 19 days of age. Information about their sows, piglet weights, and piglet serum immunoglobulin-G (IgG) and serum total protein concentrations also were recorded and assessed in relation to anti-PCV2 antibody titers. This analysis permitted characterization of the variability in anti-PCV2 MDA titers among littermates and the identification of the factors contributing to this variability. Additionally, this study sought to define an approach for identifying piglets with an elevated risk of PCV2 infection, based on low pre-vaccination antibody titers, using practical indicators applicable in the field. Results Anti-PCV2 MDA titer dynamics The individual anti-PCV2 antibody dynamics of the piglets in each litter are illustrated in Fig. 1 . With the exception of two piglets born from Sow A, the highest anti-PCV2 MDA titers were observed at 1 or 3 days of age, followed by a subsequent decline. The mean maximum sample-to-positive (S/P) ratios among litters born from each of the five sows differed significantly ( p < 0.001). The mean log10 antibody titers at 3 days of age were 3.73 (95% confidence interval [CI]: 3.70–3.76), and the mean log10 titer at 19 days of age was 3.46 (95% CI: 3.40–3.52). The half-life of the anti-PCV2 MDA was estimated to be 17.4 days (95% CI: 16.2–18.9 days). Median and range of S/P ratio, birth weight, ADWG, serum IgG concentration, and serum total protein for piglets categorized by sow The litter size, parity, median and range (minimum and maximum) of S/P ratio at 19 days of age, birth weight, peak serum IgG concentration, and serum total protein concentration at 5 days of age were determined for the piglets of each litter (Table 1 ). Comparisons were made between the means of the littermates from Sow A (with a parity of 2) and those from Sows B to E (with a parity of 5 or more). Compared to piglets of the litters from Sows B to E, piglets of the litter from Sow A exhibited significantly higher values for the mean S/P ratio at 19 days of age ( p < 0.001), birth weight ( p < 0.001), and serum total protein at 5 days of age ( p = 0.002). In contrast, no significant difference was observed between these groups for ADWG ( p = 0.932) and serum IgG concentration ( p = 0.191). Focusing on litters from sows with a parity of 5 or more, individuals with lower anti-PCV2 antibody titers at 19 days of age were observed among the litters from Sows C and E (see Fig. 1 and Table 1 ). Compared to piglets from Sows B and D, piglets from Sows C and E had significantly higher birth weights ( p = 0.002) and significantly lower serum total protein concentration at 5 days of age ( p = 0.024). Table 1 Values for each litter and comparison results. Sow Litter size Parity PCV2 S/P ratio at 19 days Birth weight (kg) ADWG (kg/day) Peak IgG (mg/mL) Total protein at 5 days (g/dL) A 8 2 1.98 (1.90–2.49) 1.93 (1.77–2.24) 0.22 (0.18–0.24) 34.4 (29.8–41.1) 5.9 (5.4-6.0) B 7 5 1.08 (0.97–1.27) 1.46 (1.17–1.85) 0.26 (0.16–0.32) 29.8 (20.9–51.2) 5.2 (4.8–6.4) C 8 6 0.74 (0.53–1.15) 1.69 (1.56–1.92) 0.20 (0.13–0.25) 22.9 (17.2–46.7) 4.6 (3.6–5.6) D 8 6 1.37 (1.23–1.62) 1.30 (1.18–1.75) 0.21 (0.15–0.32) 33.7 (14.1–51.2) 5.2 (4.6–6.4) E 8 8 1.18 (0.73–1.39) 1.60 (1.41–1.92) 0.21 (0.15–0.24) 31.7 (14.8–46.7) 4.7 (4.2–6.2) Wilcoxon rank sum test (Litter of Sow A vs. litters from the other sows) p < 0.001 p < 0.001 p = 0.932 p = 0.191 p = 0.002 The litter, parity, and median and range (minimum and maximum) of S/P ratio at 19 days of age, birth weight, average daily weight gain (ADWG [kg/day]), peak IgG concentration, and total protein concentration at 5 days of age are presented for each litter, along with p values of the Wilcoxon rank sum test comparing the mean values in piglets from Sow A to those from the other sows. Correlation between anti-PCV2 antibody titer, birth weight, and serum total protein Using the data from the litters of Sows C and E, which had piglets with lower titers, the characteristics of individuals with low anti-PCV2 antibody titers were examined. Within the litter of Sow C, a significantly positive correlation was observed between birth weight and S/P ratio at 19 days (ρ = 0.79, p = 0.028; Fig. 2 a). A moderate correlation was observed between serum total protein and S/P ratio, although this effect was not statistically significant ( ρ = 0.69, p = 0.069; Fig. 2 b). Within the litter of Sow E, no significant correlation was detected between birth weight and S/P ratio ( ρ = 0.49, p = 0.217; Fig. 2 a), although a strong and significant correlation was observed between serum total protein and S/P ratio ( ρ = 0.85, p = 0.007; Fig. 2 b). Discussion In the study, the dynamics of the pre-vaccination serum anti-PCV2 antibody titers, from birth to 19 days post-natal, were observed in 39 piglets born from five sows. Additionally, relationships between antibody titers and birth weight, ADWG, serum IgG concentration, and serum total protein were described. This enabled the identification of characteristics of individuals at elevated risk of PCV2 infection. Firstly, regarding the anti-PCV2 antibody titer dynamics, the calculated half-life (17.4 days) in this study was similar to the 17.7-day half-life provided by previous research [ 11 ]. McKeown et al. [ 12 ] reported that anti-PCV2 MDA with an S/P ratio > 0.5 is not entirely effective but offers some level of protection. In this study, since all individuals had S/P ratios exceeding 0.5 until 19 days of age, it was observed that effective MDA levels were maintained prior to vaccination (at 3 weeks of age). It has been reported that even with high MDA at the time of vaccination, there is no interference with immune response [ 13 ], therefore vaccination would likely provide protection post-vaccination for the piglets. However, given the significant variation in antibody titers observed among litters and individuals in the present study, characteristics of individuals with low antibody titers, potentially indicating elevated risk of PCV2 infection, were identified. Piglets from a sow with 2 parities exhibited higher anti-PCV2 antibody titers than piglets from sows with 5 or more parities. Notably, there was a suggestion of lower MDA in piglets from sows with higher parities. Previous studies have reported no significant relationship between anti-PCV2 MDA levels and the parity of their sows [ 14 ], although that comparison differed from ours in comparing primiparous sows and multiparous sows. Additionally, the present study indicated that both birth weight and serum total protein concentration at 5 days of age were significantly higher in piglets from a sow with 2 parities compared to those from sows with 5 or more parities. However, no significant difference was observed (between piglets from sows of differing parities) in peak serum IgG levels. This result is inconsistent with previous studies reporting higher IgG concentrations in piglets born from multiparous sows compared to primiparous sows [ 15 , 16 ]; this discrepancy again may reflect the comparison, in the present study, among multiparous sows. Further analyses revealed that among litters born to sows with five or more parities, litters with piglets having particularly low antibody titers at 19 days of age had higher mean birth weights than litters with no individuals having low antibody titers. Furthermore, within these litters, a positive correlation was observed between antibody titer and birth weight. This suggests that among the high mean birth weight litters born to sows with a high number of parities (≥ 5), piglets with low birth weight may serve as biomarkers of low antibody titer. Additionally, in litters with high mean birth weight, anti-PCV2 antibody titers exhibited positive correlations with 5-day serum total protein concentration. Similar to birth weight, serum total protein concentration suggested that it may be a valuable indicator for identifying piglets which could be at elevated risk of infection. The major limitation of the present study is the small sample size. Due to the limited data from only one young sow (with a parity of two), the reliability of comparisons to sows having five or more parities is compromised. Additionally, anti-PCV2 antibody titers in the sows themselves were not measured, so any relationship between sow antibody titer and piglet MDA was not evaluated. However, despite these limitations, the present study revealed the potential to identify piglets with low anti-PCV2 antibody titers using easily measurable indicators such as sow parity, piglet birth weight, and serum total protein concentration. The individuals observed in this study were found to possess sufficient MDA, suggesting a high likelihood of protection. However, it is noted that without appropriate vaccination to induce cellular immunity, complete protection may not be achieved [ 17 ]. PCV2 is known to be a highly resilient virus in the environment [ 18 ]. Considering pigs are constantly exposed to it, the information presented in this study may prove beneficial in preventing the spread of PCV2 infection in the field. Conclusion In the present study, pre-vaccination serum anti-PCV2 MDA titers, from birth to 19 days, were monitored in 39 piglets born to five sows. Additionally, several characteristics of piglets at elevated risk of PCV2 infection were identified. Anti-PCV2 MDA levels varied among litters, with a notable trend to lower antibody titers in piglets born from sows with higher parities. Moreover, within litters of piglets from sows with a large number of parities, those with larger mean birth weights exhibited greater variability in antibody titers. This observation suggests that piglets with lower birth weights or lower serum total protein concentrations are more likely to have lower antibody titers, particularly in litters with higher mean birth weights. Hence, factors easily observable in the field (including sow parity, piglet birth weight, and piglet serum total protein concentration) may serve as effective biomarkers for identifying piglets at elevated risk of PCV2 infection. Methods Samples From March to April 2019, serum samples were collected from 39 piglets born to five sows on a farm in Ibaraki Prefecture, Japan. These offspring represented eight piglets per sow, excluding one piglet lost to mortality on the day of birth. Sampling time points included postnatal days 0, 1, 3, 5, and 19. These samples were obtained as a secondary use of piglet sera collected for an investigation being conducted by the Scientific Feed Laboratory; approval for these additional experiments was obtained from the experimental ethics committee of the Scientific Feed Laboratory. The approved number of ethics for animal experiments is 19-S011 according to the animal welfare control guidelines in Japan. The five sows (designated A to E) had parity numbers of 2, 5, 6, and 8 ( n = 1, 1, 2, and 1, respectively). The body weights of the piglets were recorded at postnatal days 0, 5, 12, and 19. Indirect ELISA to detect anti-PCV2 antibodies. Antibody titers in piglet sera were assessed using an indirect enzyme-linked immunosorbent assay (ELISA; Porcine Circovirus type 2 Antibody test kit; BioChek, A Hygiena® Company, Reeuwijk, The Netherlands) [ 19 ]. Specifically, serum samples were collected at 0, 1, 3, 5, and 19 days of age, representing a span from the day of birth (after the intake of colostrum) to a few days prior to vaccination (typically occurring at three weeks of age). The resulting data were used to evaluate the dynamics of MDA titers prior to piglet vaccination. The antibody titers were defined using the S/P ratio; an S/P value of 0.5 or greater was considered positive, as suggested by the kit instructions. Each sample was assessed in duplicate; samples for which the duplicates exhibited by an absorbance difference of 0.1 or more were retested. The dynamics of anti-PCV2 MDAs were calculated as described in the kit instructions. Specifically, antibody titers were calculated from the S/P ratio using the following equation: $${\text{log}}_{10}titer=1.1\times {\text{log}}_{10}SP+3.361$$ where SP represents the observed S/P ratio. Using this formula, antibody titers at 3 days and 19 days of age were calculated. Subsequently, the calculated titers at 2 points were used to determine the slope of the line describing the decrease in antibody titer in a given litter, which was used in turn to determine the half-life of antibody concentration. The reason for choosing three days was that, based on observations of titer dynamics, the peak of titer seemed to be between the first and third day after birth, and the day immediately after the peak was chosen. Colostrum-derived IgG antibodies Serum IgG was determined as an indicator of piglet colostrum intake. Colostrum-derived IgG (in piglet serum) has been reported to peak at 2 days of age [ 20 ]; therefore, serum IgG concentrations were determined at 1 and 3 days of age in the present study. The assay was conducted using the bicinchoninic acid (BCA) protein assay (Thermo Fisher Scientific, Inc., Rockford, IL, USA) [ 21 ]. The porcine IgG ELISA standard (Mabtech, Inc., Nacka Strand, Sweden) was employed as the standard. Pilot analyses were conducted to define dilution factors, for both the standards and samples, that provided values aligned with the standard curve; the diluent consisted of phosphate-buffered saline supplemented with 0.05% Tween 20 and 0.1% bovine serum albumin. The standard curve was plotted as the log10 of standard concentrations against optical density values and was represented by a regression line connecting four points. Total protein concentration The total protein in the serum samples from piglets at 0, 1, 3, 5, and 19 days of age was determined; the resulting data were employed to assess potential relationships among anti-PCV2 antibody titers, colostrum intake, and serum total protein concentrations. Serum total protein levels were determined using a digital pocket blood serum refractometer (PAL-11S pal series; ATAGO Co., Ltd., Tokyo, Japan). Each sample was measured multiple times until a stable measurement was obtained, and the stabilized value was considered the observed value. Statistical analysis Descriptive statistics were performed at the levels of the litter and the individual piglets. The maximum anti-PCV2 S/P ratios in piglets were compared among litters from the five sows using a Kruskal-Wallis test. Moreover, the median and range within litters were determined for the following parameters: S/P ratio at 19 days, birth weight, average daily weight gain (ADWG), peak serum IgG concentration, and serum total protein concentration at 5 days. The 19-day S/P ratio was selected because this time point typically represents the final pre-vaccination value, given that vaccination against PCV2 usually occurs at 3 weeks of age. Assessment of the S/P ratio before vaccination was employed to identify individuals with insufficient MDA and, consequently, an elevated risk of infection. The ADWG was estimated by the regression model using the recorded body weights at four-time points. The 5-day serum total protein concentration was selected based on the assumption that albumin levels at this time point are influenced by hepatic synthesis, while globulin levels (derived from colostrum) will still be present [ 20 ]. Assessment of the serum total protein concentration at this early time point was employed as a biomarker indicating the piglet’s risk for infection by PCV2. The means of the 19-day S/P ratio, birth weight, serum IgG concentration, and serum total protein were compared between piglets of the litter from Sow A (with a parity of 2) and piglets of litters from Sows B-E (with parities of 5 or more) using a Wilcoxon rank-sum test. Given the significant differences observed in piglets from Sow A compared to those from the other sows, subsequent analysis was conducted exclusively on litters from Sows B-E. Upon observing the anti-PCV2 antibody titers, variability and instances of lower titers were noted in the 19-day-old piglets from Sows C and E (See “Results”). Consequently, the analysis was stratified into two groups (the first consisting of Sows C and E; the second consisting of Sows B and D) with and without observed variation in antibody titer at 19 days of age for evaluating specific characteristics. Moreover, distinctive features within the litters of Sow C and E were elucidated. The relationship between 19-day anti-PCV2 antibody titers and birth weight, as well as between 19-day PCV2 titers and serum total protein concentrations, were examined using Spearman’s rank correlation test. R version 4.3.1 was used for all statistical analyses [ 22 ]. Abbreviations ADWG Average daily weight gain ELISA Enzyme-linked immunosorbent assay IgG Immunoglobulin-G MDA Maternally derived antibody PCVAD Porcine circovirus-associated disease PCV2 Porcine circovirus type 2 S/P Sample-to-positive Declarations Ethics approval and consent to participate These samples were obtained as a secondary use of piglet sera collected for an investigation being conducted by the Scientific Feed Laboratory; approval for these additional experiments was obtained from the experimental ethics committee of the Scientific Feed Laboratory. The approved number of ethics for animal experiments is 19-S011 according to the animal welfare control guidelines in Japan. Consent for publication Not applicable. Availability of data and materials The datasets used and/or analysed during the current study are available from the corresponding author upon reasonable request. Competing interests The authors declare no competing interests. Funding This study was partly funded by the Grant-in-Aid for Graduate Students of the World-leading Innovative & Smart Education (WISE) Program (1801) from the Ministry of Education, Culture, Sports, Science, and Technology, Japan. Authors' contributions This work was carried out in collaboration between all authors. MU, KM and KH designed the experiment; TT provided the resource; MU, KH, ST and YK experimented; MU performed data analysis and figures; MU, KH and KM drafted the manuscript; all authors reviewed and approved the manuscript. Acknowledgements This study was conducted by the Grant-in-Aid for Graduate Students of the WISE Program “Program for One Health Frontier of Graduate School of Excellence” at Hokkaido University. We express our gratitude to the pig farmers and veterinarians who cooperated with this study. Authors' information (optional) Authors and Affiliations School of Veterinary Medicine, Rakuno Gakuen University, 582 Bunkyodai Midorimachi, Ebetsu, Hokkaido 069-8501, Japan Katsuro Hagiwara, Kohei Makita, Saya Taharaguchi, Yukine Kano and Makoto Ukita Scientific Feed Laboratory Co., ltd., R & D center, 7 Ojamachi, Sakura, Chiba, 285-0043 Japan Tadashi Takino Corresponding author Correspondence to Katsuro Hagiwara. References Opriessnig, T., X.J. Meng, and P.G. Halbur, Porcine circovirus type 2 associated disease: update on current terminology, clinical manifestations, pathogenesis, diagnosis, and intervention strategies. J Vet Diagn Invest, 2007. 19 (6): p. 591-615. Allan, G.M., et al., Isolation of porcine circovirus-like viruses from pigs with a wasting disease in the USA and Europe. J Vet Diagn Invest, 1998. 10 (1): p. 3-10. Calsamiglia, M., et al., Sow porcine circovirus type 2 (PCV2) status effect on litter mortality in postweaning multisystemic wasting syndrome (PMWS). Research in Veterinary Science, 2007. 82 (3): p. 299-304. Franzo, G. and J. Segalés, Porcine circovirus 2 (PCV-2) genotype update and proposal of a new genotyping methodology. PLoS One, 2018. 13 (12): p. e0208585. Link, E.K., et al., Discriminating the eight genotypes of the porcine circovirus type 2 with TaqMan-based real-time PCR. Virology Journal, 2021. 18 (1): p. 70. Fort, M., et al., Porcine circovirus type 2 (PCV2) vaccination of conventional pigs prevents viremia against PCV2 isolates of different genotypes and geographic origins. Vaccine, 2008. 26 (8): p. 1063-71. Opriessnig, T., et al., Comparison of efficacy of commercial one dose and two dose PCV2 vaccines using a mixed PRRSV-PCV2-SIV clinical infection model 2-3-months post vaccination. Vaccine, 2009. 27 (7): p. 1002-7. Opriessnig, T., et al., Emergence of a novel mutant PCV2b variant associated with clinical PCVAD in two vaccinated pig farms in the U.S. concurrently infected with PPV2. Vet Microbiol, 2013. 163 (1-2): p. 177-83. Seo, H.W., et al., Effect of porcine circovirus type 2 (PCV2) vaccination on PCV2-viremic piglets after experimental PCV2 challenge. Vet Res, 2014. 45 (1): p. 13. Martin-Valls, G.E., et al., High levels of maternally derived antibodies do not significantly interfere with the development of humoral and cell-mediated responses to Porcine circovirus 2 after intradermal vaccination. Porcine Health Manag, 2023. 9 (1): p. 40. Polo, J., et al., Half-life of porcine antibodies absorbed from a colostrum supplement containing porcine immunoglobulins. J Anim Sci, 2012. 90 Suppl 4 : p. 308-10. McKeown, N.E., et al., Effects of porcine circovirus type 2 (PCV2) maternal antibodies on experimental infection of piglets with PCV2. Clin Diagn Lab Immunol, 2005. 12 (11): p. 1347-51. Figueras-Gourgues, S., et al., Effect of Porcine circovirus 2 (PCV-2) maternally derived antibodies on performance and PCV-2 viremia in vaccinated piglets under field conditions. Porcine Health Management, 2019. 5 (1): p. 21. Sibila, M., et al., Descriptive analyses of maternally-derived antibody levels against porcine circovirus 2 (PCV-2) in 3- and 21-day-old piglets from farms of four European countries using different vaccination protocols in sows. Porcine Health Manag, 2022. 8 (1): p. 41. Piñeiro, C., et al., Influence of sows' parity on performance and humoral immune response of the offspring. Porcine Health Manag, 2019. 5 : p. 1. Nuntapaitoon, M., et al., Impact of parity and housing conditions on concentration of immunoglobulin G in sow colostrum. Trop Anim Health Prod, 2019. 51 (5): p. 1239-1246. Fenaux, M., et al., Immunogenicity and pathogenicity of chimeric infectious DNA clones of pathogenic porcine circovirus type 2 (PCV2) and nonpathogenic PCV1 in weanling pigs. J Virol, 2003. 77 (20): p. 11232-43. López-Lorenzo, G., et al., Presence of Porcine Circovirus Type 2 in the Environment of Farm Facilities without Pigs in Long Term-Vaccinated Farrow-to-Wean Farms. Animals (Basel), 2022. 12 (24). Pileri, E., et al., Comparison of the immunoperoxidase monolayer assay and three commercial ELISAs for detection of antibodies against porcine circovirus type 2. Vet J, 2014. 201 (3): p. 429-32. Tóthová, C., et al., Serum protein electrophoretic pattern in piglets during the early postnatal period. Sci Rep, 2021. 11 (1): p. 17539. Smith, P.K., et al., Measurement of protein using bicinchoninic acid. Anal Biochem, 1985. 150 (1): p. 76-85. R Core Team, R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. 2023. 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-4182328","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":288397570,"identity":"b1ad56cd-e16c-4fa8-81df-32ae1751f28d","order_by":0,"name":"Makoto Ukita","email":"","orcid":"","institution":"Rakuno Gakuen University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Makoto","middleName":"","lastName":"Ukita","suffix":""},{"id":288397573,"identity":"545aa4de-efc8-4eeb-afa2-5c1d9fab2ff0","order_by":1,"name":"Yukine Kano","email":"","orcid":"","institution":"Rakuno Gakuen University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yukine","middleName":"","lastName":"Kano","suffix":""},{"id":288397575,"identity":"eabf3f16-f519-4de1-8fea-a3e6e48a044c","order_by":2,"name":"Saya Taharaguchi","email":"","orcid":"","institution":"Rakuno Gakuen University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Saya","middleName":"","lastName":"Taharaguchi","suffix":""},{"id":288397576,"identity":"84bdd09e-0964-49c1-81da-e868c0320f6c","order_by":3,"name":"Tadashi Takino","email":"","orcid":"","institution":"Scientific Feed Laboratory Co., ltd.","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Tadashi","middleName":"","lastName":"Takino","suffix":""},{"id":288397577,"identity":"d20d11ed-7662-40ac-b592-aaefa9d0d5cc","order_by":4,"name":"Kohei Makita","email":"","orcid":"","institution":"Rakuno Gakuen University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Kohei","middleName":"","lastName":"Makita","suffix":""},{"id":288397581,"identity":"9fbaf090-088e-4371-8707-347d237d0b93","order_by":5,"name":"Katsuro Hagiwara","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA3ElEQVRIiWNgGAWjYBACCQYeIGlgwwCmIeAAUVrSSNbCcBhZCwEg2cB78OOXgvP5/D1nzB58YLCTZ2A8i98aaQa+ZGkZg9uWM872mBvOYEg2bGA4l4BXi5z8GwNpCYPbBgznecykeRiYgcrPGODXwsBj/FvC4JyBPERLPWEt0gw8ZpIfDA4YGJztAWk5TFiLZAOPmTWDQbKB4ZljZZIzDI4bthHyi8QBHuObP/7YGcidSd4m8aGiWp5fgkCIgQAzIkqATmKTOENQBwPjDxQufw9hLaNgFIyCUTCiAABHWDua8hSESQAAAABJRU5ErkJggg==","orcid":"","institution":"Rakuno Gakuen University","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Katsuro","middleName":"","lastName":"Hagiwara","suffix":""}],"badges":[],"createdAt":"2024-03-28 12:41:59","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4182328/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4182328/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":54362836,"identity":"ffda31fe-4106-4e31-b0b6-f15db67a5295","added_by":"auto","created_at":"2024-04-09 11:40:01","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":337030,"visible":true,"origin":"","legend":"\u003cp\u003eIndividual dynamics of anti-PCV2 antibody titers in piglets, grouped by litter (Sows A to E, \u003cem\u003en\u003c/em\u003e = 8, 7, 8, 8, and 8, respectively). The number of parities for the sows were 2, 5, 6, 6, and 8, respectively.\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-4182328/v1/f10f99a6e0a358bb2bd57f5e.png"},{"id":54362837,"identity":"6c298984-9d79-46c9-ae39-3958deb7a228","added_by":"auto","created_at":"2024-04-09 11:40:02","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":262035,"visible":true,"origin":"","legend":"\u003cp\u003eRelationships within the litters of Sow C (red points and lines) and Sow E (blue points and lines): (a) between birth weight (kg) and S/P ratio at 19 days (Sow C: \u003cem\u003eρ\u003c/em\u003e = 0.79, \u003cem\u003ep\u003c/em\u003e = 0.028; Sow E: \u003cem\u003eρ\u003c/em\u003e = 0.49, \u003cem\u003ep\u003c/em\u003e = 0.217), and (b) between total protein (g/dL) and S/P ratio at 19 days (Sow C: \u003cem\u003eρ\u003c/em\u003e = 0.69, \u003cem\u003ep\u003c/em\u003e = 0.069; Sow E: \u003cem\u003eρ\u003c/em\u003e = 0.85, \u003cem\u003ep\u003c/em\u003e = 0.007).\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-4182328/v1/f73c2a45599071e6c1227d70.png"},{"id":56425750,"identity":"3df9fae6-33da-4616-bfe3-6397fb058908","added_by":"auto","created_at":"2024-05-14 04:24:19","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":812367,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4182328/v1/cb97107b-2236-4609-8f00-bef0c3a379ba.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Characterization of maternally derived antibody titers against porcine circovirus type 2 in serum of piglets and identification of piglets at elevated risk of infection","fulltext":[{"header":"Background","content":"\u003cp\u003ePorcine circovirus type 2 (PCV2) is commonly associated with several clinical syndromes and diseases collectively referred to as porcine circovirus-associated disease (PCVAD) [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e], in weaned 5 to 12 weeks of age [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], which has a significant economic impact on the global swine industry [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. PCV2 is a member of the genus \u003cem\u003eCircovirus\u003c/em\u003e, of the family \u003cem\u003eCircoviridae\u003c/em\u003e, the smallest non-enveloped, single-stranded, circular DNA virus that replicates autonomously in mammalian cells. PCV2 is currently classified into eight genotypes, labeled as PCV2a to PCV2h [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Until 2007, PCVAD outbreaks across the globe were associated primarily with PCV2b; the subsequent development and implementation of an anti-PCV2 vaccine based on a PCV2a antigen led to a reduction in the number of cases [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. However, in 2012, PCVAD cases caused by PCV2d were reported in North America on farms employing the PCV2a-based vaccine [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. More recently, PCV2d-2 has emerged as the predominant genotype worldwide. In Japan, the prevalence of anti-PCV2 antibody positivity in pig farms exceeds 90%, and most farms have implemented vaccination for 3-week-old piglets and/or sows three weeks before farrowing.\u003c/p\u003e \u003cp\u003eOn farms that vaccinate only piglets, the titer of anti-PCV2 antibodies in breeding sows depends on the natural infection of these animals, meaning that sows exhibit a wide range of antibody titers. Similarly, the maternally derived antibody (MDA) titers among the offspring of these sows exhibit large variations. Piglets with low MDA titers can be infected before vaccination. In previous studies, tracking the anti-PCV2 antibody titers of piglets at three weeks (pre-vaccination) and older (post-vaccination) revealed that the immune response was based on the level of antibody titers at the time of vaccination in experimental and field-level studies [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. However, few studies have tracked anti-PCV2 MDA in serum from immediately after birth through vaccination and evaluated antibody titer dynamics and factors affecting these dynamics at the individual level. On Japanese farms, piglets typically are moved to weaning pig pens at three weeks of age and raised in herds. Any piglet that is infected with PCV2 prior to that move has the potential to serve as a source for the spread of infection to the herd. Therefore, it is crucial to identify piglets at high risk of infection in the field, especially those that lack sufficient pre-vaccination anti-PCV2 antibody titers at three weeks of age, which would increase the likelihood of infection.\u003c/p\u003e \u003cp\u003eIn the present study, pre-vaccination titers of anti-PCV2 antibodies in the serum of piglets were measured repeatedly from birth to 19 days of age. Information about their sows, piglet weights, and piglet serum immunoglobulin-G (IgG) and serum total protein concentrations also were recorded and assessed in relation to anti-PCV2 antibody titers. This analysis permitted characterization of the variability in anti-PCV2 MDA titers among littermates and the identification of the factors contributing to this variability. Additionally, this study sought to define an approach for identifying piglets with an elevated risk of PCV2 infection, based on low pre-vaccination antibody titers, using practical indicators applicable in the field.\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eAnti-PCV2 MDA titer dynamics\u003c/h2\u003e \u003cp\u003eThe individual anti-PCV2 antibody dynamics of the piglets in each litter are illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. With the exception of two piglets born from Sow A, the highest anti-PCV2 MDA titers were observed at 1 or 3 days of age, followed by a subsequent decline. The mean maximum sample-to-positive (S/P) ratios among litters born from each of the five sows differed significantly (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The mean log10 antibody titers at 3 days of age were 3.73 (95% confidence interval [CI]: 3.70\u0026ndash;3.76), and the mean log10 titer at 19 days of age was 3.46 (95% CI: 3.40\u0026ndash;3.52). The half-life of the anti-PCV2 MDA was estimated to be 17.4 days (95% CI: 16.2\u0026ndash;18.9 days).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cem\u003eMedian and range of S/P ratio, birth weight, ADWG, serum IgG concentration, and serum total protein for piglets categorized by sow\u003c/em\u003e \u003c/p\u003e \u003cp\u003eThe litter size, parity, median and range (minimum and maximum) of S/P ratio at 19 days of age, birth weight, peak serum IgG concentration, and serum total protein concentration at 5 days of age were determined for the piglets of each litter (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Comparisons were made between the means of the littermates from Sow A (with a parity of 2) and those from Sows B to E (with a parity of 5 or more). Compared to piglets of the litters from Sows B to E, piglets of the litter from Sow A exhibited significantly higher values for the mean S/P ratio at 19 days of age (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), birth weight (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), and serum total protein at 5 days of age (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.002). In contrast, no significant difference was observed between these groups for ADWG (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.932) and serum IgG concentration (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.191).\u003c/p\u003e \u003cp\u003eFocusing on litters from sows with a parity of 5 or more, individuals with lower anti-PCV2 antibody titers at 19 days of age were observed among the litters from Sows C and E (see Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Compared to piglets from Sows B and D, piglets from Sows C and E had significantly higher birth weights (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.002) and significantly lower serum total protein concentration at 5 days of age (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.024).\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\u003eValues for each litter and comparison results.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSow\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLitter size\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eParity\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePCV2 S/P ratio\u003c/p\u003e \u003cp\u003eat 19 days\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eBirth weight (kg)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eADWG (kg/day)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003ePeak IgG (mg/mL)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eTotal protein\u003c/p\u003e \u003cp\u003eat 5 days (g/dL)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.98\u003c/p\u003e \u003cp\u003e(1.90\u0026ndash;2.49)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.93\u003c/p\u003e \u003cp\u003e(1.77\u0026ndash;2.24)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.22\u003c/p\u003e \u003cp\u003e(0.18\u0026ndash;0.24)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e34.4\u003c/p\u003e \u003cp\u003e(29.8\u0026ndash;41.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e5.9 (5.4-6.0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.08\u003c/p\u003e \u003cp\u003e(0.97\u0026ndash;1.27)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.46\u003c/p\u003e \u003cp\u003e(1.17\u0026ndash;1.85)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.26\u003c/p\u003e \u003cp\u003e(0.16\u0026ndash;0.32)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e29.8\u003c/p\u003e \u003cp\u003e(20.9\u0026ndash;51.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e5.2 (4.8\u0026ndash;6.4)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.74\u003c/p\u003e \u003cp\u003e(0.53\u0026ndash;1.15)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.69\u003c/p\u003e \u003cp\u003e(1.56\u0026ndash;1.92)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.20\u003c/p\u003e \u003cp\u003e(0.13\u0026ndash;0.25)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e22.9\u003c/p\u003e \u003cp\u003e(17.2\u0026ndash;46.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e4.6 (3.6\u0026ndash;5.6)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.37\u003c/p\u003e \u003cp\u003e(1.23\u0026ndash;1.62)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.30\u003c/p\u003e \u003cp\u003e(1.18\u0026ndash;1.75)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.21\u003c/p\u003e \u003cp\u003e(0.15\u0026ndash;0.32)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e33.7\u003c/p\u003e \u003cp\u003e(14.1\u0026ndash;51.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e5.2 (4.6\u0026ndash;6.4)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eE\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.18\u003c/p\u003e \u003cp\u003e(0.73\u0026ndash;1.39)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.60\u003c/p\u003e \u003cp\u003e(1.41\u0026ndash;1.92)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.21\u003c/p\u003e \u003cp\u003e(0.15\u0026ndash;0.24)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e31.7\u003c/p\u003e \u003cp\u003e(14.8\u0026ndash;46.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e4.7 (4.2\u0026ndash;6.2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003eWilcoxon rank sum test\u003c/p\u003e \u003cp\u003e(Litter of Sow A vs. litters from the other sows)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.932\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.191\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.002\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\u003eThe litter, parity, and median and range (minimum and maximum) of S/P ratio at 19 days of age, birth weight, average daily weight gain (ADWG [kg/day]), peak IgG concentration, and total protein concentration at 5 days of age are presented for each litter, along with \u003cem\u003ep\u003c/em\u003e values of the Wilcoxon rank sum test comparing the mean values in piglets from Sow A to those from the other sows.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eCorrelation between anti-PCV2 antibody titer, birth weight, and serum total protein\u003c/h2\u003e \u003cp\u003eUsing the data from the litters of Sows C and E, which had piglets with lower titers, the characteristics of individuals with low anti-PCV2 antibody titers were examined. Within the litter of Sow C, a significantly positive correlation was observed between birth weight and S/P ratio at 19 days (ρ\u0026thinsp;=\u0026thinsp;0.79, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.028; Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). A moderate correlation was observed between serum total protein and S/P ratio, although this effect was not statistically significant (\u003cem\u003eρ\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.69, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.069; Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). Within the litter of Sow E, no significant correlation was detected between birth weight and S/P ratio (\u003cem\u003eρ\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.49, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.217; Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea), although a strong and significant correlation was observed between serum total protein and S/P ratio (\u003cem\u003eρ\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.85, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.007; Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn the study, the dynamics of the pre-vaccination serum anti-PCV2 antibody titers, from birth to 19 days post-natal, were observed in 39 piglets born from five sows. Additionally, relationships between antibody titers and birth weight, ADWG, serum IgG concentration, and serum total protein were described. This enabled the identification of characteristics of individuals at elevated risk of PCV2 infection.\u003c/p\u003e \u003cp\u003eFirstly, regarding the anti-PCV2 antibody titer dynamics, the calculated half-life (17.4 days) in this study was similar to the 17.7-day half-life provided by previous research [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. McKeown et al. [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] reported that anti-PCV2 MDA with an S/P ratio\u0026thinsp;\u0026gt;\u0026thinsp;0.5 is not entirely effective but offers some level of protection. In this study, since all individuals had S/P ratios exceeding 0.5 until 19 days of age, it was observed that effective MDA levels were maintained prior to vaccination (at 3 weeks of age). It has been reported that even with high MDA at the time of vaccination, there is no interference with immune response [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], therefore vaccination would likely provide protection post-vaccination for the piglets. However, given the significant variation in antibody titers observed among litters and individuals in the present study, characteristics of individuals with low antibody titers, potentially indicating elevated risk of PCV2 infection, were identified.\u003c/p\u003e \u003cp\u003ePiglets from a sow with 2 parities exhibited higher anti-PCV2 antibody titers than piglets from sows with 5 or more parities. Notably, there was a suggestion of lower MDA in piglets from sows with higher parities. Previous studies have reported no significant relationship between anti-PCV2 MDA levels and the parity of their sows [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], although that comparison differed from ours in comparing primiparous sows and multiparous sows. Additionally, the present study indicated that both birth weight and serum total protein concentration at 5 days of age were significantly higher in piglets from a sow with 2 parities compared to those from sows with 5 or more parities. However, no significant difference was observed (between piglets from sows of differing parities) in peak serum IgG levels. This result is inconsistent with previous studies reporting higher IgG concentrations in piglets born from multiparous sows compared to primiparous sows [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]; this discrepancy again may reflect the comparison, in the present study, among multiparous sows.\u003c/p\u003e \u003cp\u003eFurther analyses revealed that among litters born to sows with five or more parities, litters with piglets having particularly low antibody titers at 19 days of age had higher mean birth weights than litters with no individuals having low antibody titers. Furthermore, within these litters, a positive correlation was observed between antibody titer and birth weight. This suggests that among the high mean birth weight litters born to sows with a high number of parities (\u0026ge;\u0026thinsp;5), piglets with low birth weight may serve as biomarkers of low antibody titer. Additionally, in litters with high mean birth weight, anti-PCV2 antibody titers exhibited positive correlations with 5-day serum total protein concentration. Similar to birth weight, serum total protein concentration suggested that it may be a valuable indicator for identifying piglets which could be at elevated risk of infection. The major limitation of the present study is the small sample size. Due to the limited data from only one young sow (with a parity of two), the reliability of comparisons to sows having five or more parities is compromised. Additionally, anti-PCV2 antibody titers in the sows themselves were not measured, so any relationship between sow antibody titer and piglet MDA was not evaluated. However, despite these limitations, the present study revealed the potential to identify piglets with low anti-PCV2 antibody titers using easily measurable indicators such as sow parity, piglet birth weight, and serum total protein concentration. The individuals observed in this study were found to possess sufficient MDA, suggesting a high likelihood of protection. However, it is noted that without appropriate vaccination to induce cellular immunity, complete protection may not be achieved [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. PCV2 is known to be a highly resilient virus in the environment [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Considering pigs are constantly exposed to it, the information presented in this study may prove beneficial in preventing the spread of PCV2 infection in the field.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn the present study, pre-vaccination serum anti-PCV2 MDA titers, from birth to 19 days, were monitored in 39 piglets born to five sows. Additionally, several characteristics of piglets at elevated risk of PCV2 infection were identified. Anti-PCV2 MDA levels varied among litters, with a notable trend to lower antibody titers in piglets born from sows with higher parities. Moreover, within litters of piglets from sows with a large number of parities, those with larger mean birth weights exhibited greater variability in antibody titers. This observation suggests that piglets with lower birth weights or lower serum total protein concentrations are more likely to have lower antibody titers, particularly in litters with higher mean birth weights. Hence, factors easily observable in the field (including sow parity, piglet birth weight, and piglet serum total protein concentration) may serve as effective biomarkers for identifying piglets at elevated risk of PCV2 infection.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eSamples\u003c/h2\u003e \u003cp\u003eFrom March to April 2019, serum samples were collected from 39 piglets born to five sows on a farm in Ibaraki Prefecture, Japan. These offspring represented eight piglets per sow, excluding one piglet lost to mortality on the day of birth. Sampling time points included postnatal days 0, 1, 3, 5, and 19. These samples were obtained as a secondary use of piglet sera collected for an investigation being conducted by the Scientific Feed Laboratory; approval for these additional experiments was obtained from the experimental ethics committee of the Scientific Feed Laboratory. The approved number of ethics for animal experiments is 19-S011 according to the animal welfare control guidelines in Japan. The five sows (designated A to E) had parity numbers of 2, 5, 6, and 8 (\u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1, 1, 2, and 1, respectively). The body weights of the piglets were recorded at postnatal days 0, 5, 12, and 19.\u003c/p\u003e \u003cp\u003e \u003cem\u003eIndirect ELISA to detect anti-PCV2 antibodies.\u003c/em\u003e \u003c/p\u003e \u003cp\u003eAntibody titers in piglet sera were assessed using an indirect enzyme-linked immunosorbent assay (ELISA; Porcine Circovirus type 2 Antibody test kit; BioChek, A Hygiena\u0026reg; Company, Reeuwijk, The Netherlands) [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Specifically, serum samples were collected at 0, 1, 3, 5, and 19 days of age, representing a span from the day of birth (after the intake of colostrum) to a few days prior to vaccination (typically occurring at three weeks of age). The resulting data were used to evaluate the dynamics of MDA titers prior to piglet vaccination. The antibody titers were defined using the S/P ratio; an S/P value of 0.5 or greater was considered positive, as suggested by the kit instructions. Each sample was assessed in duplicate; samples for which the duplicates exhibited by an absorbance difference of 0.1 or more were retested.\u003c/p\u003e \u003cp\u003eThe dynamics of anti-PCV2 MDAs were calculated as described in the kit instructions. Specifically, antibody titers were calculated from the S/P ratio using the following equation:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$${\\text{log}}_{10}titer=1.1\\times {\\text{log}}_{10}SP+3.361$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere \u003cem\u003eSP\u003c/em\u003e represents the observed S/P ratio. Using this formula, antibody titers at 3 days and 19 days of age were calculated. Subsequently, the calculated titers at 2 points were used to determine the slope of the line describing the decrease in antibody titer in a given litter, which was used in turn to determine the half-life of antibody concentration. The reason for choosing three days was that, based on observations of titer dynamics, the peak of titer seemed to be between the first and third day after birth, and the day immediately after the peak was chosen.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eColostrum-derived IgG antibodies\u003c/h3\u003e\n\u003cp\u003eSerum IgG was determined as an indicator of piglet colostrum intake. Colostrum-derived IgG (in piglet serum) has been reported to peak at 2 days of age [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]; therefore, serum IgG concentrations were determined at 1 and 3 days of age in the present study. The assay was conducted using the bicinchoninic acid (BCA) protein assay (Thermo Fisher Scientific, Inc., Rockford, IL, USA) [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The porcine IgG ELISA standard (Mabtech, Inc., Nacka Strand, Sweden) was employed as the standard. Pilot analyses were conducted to define dilution factors, for both the standards and samples, that provided values aligned with the standard curve; the diluent consisted of phosphate-buffered saline supplemented with 0.05% Tween 20 and 0.1% bovine serum albumin. The standard curve was plotted as the log10 of standard concentrations against optical density values and was represented by a regression line connecting four points.\u003c/p\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eTotal protein concentration\u003c/h2\u003e \u003cp\u003eThe total protein in the serum samples from piglets at 0, 1, 3, 5, and 19 days of age was determined; the resulting data were employed to assess potential relationships among anti-PCV2 antibody titers, colostrum intake, and serum total protein concentrations. Serum total protein levels were determined using a digital pocket blood serum refractometer (PAL-11S pal series; ATAGO Co., Ltd., Tokyo, Japan). Each sample was measured multiple times until a stable measurement was obtained, and the stabilized value was considered the observed value.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eDescriptive statistics were performed at the levels of the litter and the individual piglets. The maximum anti-PCV2 S/P ratios in piglets were compared among litters from the five sows using a Kruskal-Wallis test. Moreover, the median and range within litters were determined for the following parameters: S/P ratio at 19 days, birth weight, average daily weight gain (ADWG), peak serum IgG concentration, and serum total protein concentration at 5 days. The 19-day S/P ratio was selected because this time point typically represents the final pre-vaccination value, given that vaccination against PCV2 usually occurs at 3 weeks of age. Assessment of the S/P ratio before vaccination was employed to identify individuals with insufficient MDA and, consequently, an elevated risk of infection. The ADWG was estimated by the regression model using the recorded body weights at four-time points. The 5-day serum total protein concentration was selected based on the assumption that albumin levels at this time point are influenced by hepatic synthesis, while globulin levels (derived from colostrum) will still be present [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Assessment of the serum total protein concentration at this early time point was employed as a biomarker indicating the piglet\u0026rsquo;s risk for infection by PCV2.\u003c/p\u003e \u003cp\u003eThe means of the 19-day S/P ratio, birth weight, serum IgG concentration, and serum total protein were compared between piglets of the litter from Sow A (with a parity of 2) and piglets of litters from Sows B-E (with parities of 5 or more) using a Wilcoxon rank-sum test. Given the significant differences observed in piglets from Sow A compared to those from the other sows, subsequent analysis was conducted exclusively on litters from Sows B-E.\u003c/p\u003e \u003cp\u003eUpon observing the anti-PCV2 antibody titers, variability and instances of lower titers were noted in the 19-day-old piglets from Sows C and E (See \u0026ldquo;Results\u0026rdquo;). Consequently, the analysis was stratified into two groups (the first consisting of Sows C and E; the second consisting of Sows B and D) with and without observed variation in antibody titer at 19 days of age for evaluating specific characteristics. Moreover, distinctive features within the litters of Sow C and E were elucidated. The relationship between 19-day anti-PCV2 antibody titers and birth weight, as well as between 19-day PCV2 titers and serum total protein concentrations, were examined using Spearman\u0026rsquo;s rank correlation test. R version 4.3.1 was used for all statistical analyses [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eADWG\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eAverage daily weight gain\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eELISA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eEnzyme-linked immunosorbent assay\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eIgG\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eImmunoglobulin-G\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eMDA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMaternally derived antibody\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003ePCVAD\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ePorcine circovirus-associated disease\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003ePCV2\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ePorcine circovirus type 2\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eS/P\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSample-to-positive\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThese samples were obtained as a secondary use of piglet sera collected for an investigation being conducted by the Scientific Feed Laboratory; approval for these additional experiments was obtained from the experimental ethics committee of the Scientific Feed Laboratory. The approved number of ethics for animal experiments is 19-S011 according to the animal welfare control guidelines in Japan.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analysed during the current study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was partly funded by the Grant-in-Aid for Graduate Students of the World-leading Innovative \u0026amp; Smart Education (WISE) Program (1801) from the Ministry of Education, Culture, Sports, Science, and Technology, Japan.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was carried out in collaboration between all authors. MU, KM and KH designed the experiment; TT provided the resource; MU, KH, ST and YK experimented; MU performed data analysis and figures; MU, KH and KM drafted the manuscript; all authors reviewed and approved the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was conducted by the Grant-in-Aid for Graduate Students of the WISE Program \u0026ldquo;Program for One Health Frontier of Graduate School of Excellence\u0026rdquo; at Hokkaido University. We express our gratitude to the pig farmers and veterinarians who cooperated with this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; information (optional)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAuthors and Affiliations\u003c/p\u003e\n\u003cp\u003eSchool of Veterinary Medicine, Rakuno Gakuen University, 582 Bunkyodai Midorimachi, Ebetsu, Hokkaido 069-8501, Japan\u003c/p\u003e\n\u003cp\u003eKatsuro Hagiwara, Kohei Makita, Saya Taharaguchi, Yukine Kano and Makoto Ukita\u003c/p\u003e\n\u003cp\u003eScientific Feed Laboratory Co., ltd., R \u0026amp; D center, 7 Ojamachi, Sakura, Chiba, 285-0043 Japan\u003c/p\u003e\n\u003cp\u003eTadashi Takino\u003c/p\u003e\n\u003cp\u003eCorresponding author\u003c/p\u003e\n\u003cp\u003eCorrespondence to Katsuro Hagiwara.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eOpriessnig, T., X.J. Meng, and P.G. Halbur, \u003cem\u003ePorcine circovirus type 2 associated disease: update on current terminology, clinical manifestations, pathogenesis, diagnosis, and intervention strategies.\u003c/em\u003e J Vet Diagn Invest, 2007. \u003cstrong\u003e19\u003c/strong\u003e(6): p. 591-615.\u003c/li\u003e\n\u003cli\u003eAllan, G.M., et al., \u003cem\u003eIsolation of porcine circovirus-like viruses from pigs with a wasting disease in the USA and Europe.\u003c/em\u003e J Vet Diagn Invest, 1998. \u003cstrong\u003e10\u003c/strong\u003e(1): p. 3-10.\u003c/li\u003e\n\u003cli\u003eCalsamiglia, M., et al., \u003cem\u003eSow porcine circovirus type 2 (PCV2) status effect on litter mortality in postweaning multisystemic wasting syndrome (PMWS).\u003c/em\u003e Research in Veterinary Science, 2007. \u003cstrong\u003e82\u003c/strong\u003e(3): p. 299-304.\u003c/li\u003e\n\u003cli\u003eFranzo, G. and J. Segal\u0026eacute;s, \u003cem\u003ePorcine circovirus 2 (PCV-2) genotype update and proposal of a new genotyping methodology.\u003c/em\u003e PLoS One, 2018. \u003cstrong\u003e13\u003c/strong\u003e(12): p. e0208585.\u003c/li\u003e\n\u003cli\u003eLink, E.K., et al., \u003cem\u003eDiscriminating the eight genotypes of the porcine circovirus type 2 with TaqMan-based real-time PCR.\u003c/em\u003e Virology Journal, 2021. \u003cstrong\u003e18\u003c/strong\u003e(1): p. 70.\u003c/li\u003e\n\u003cli\u003eFort, M., et al., \u003cem\u003ePorcine circovirus type 2 (PCV2) vaccination of conventional pigs prevents viremia against PCV2 isolates of different genotypes and geographic origins.\u003c/em\u003e Vaccine, 2008. \u003cstrong\u003e26\u003c/strong\u003e(8): p. 1063-71.\u003c/li\u003e\n\u003cli\u003eOpriessnig, T., et al., \u003cem\u003eComparison of efficacy of commercial one dose and two dose PCV2 vaccines using a mixed PRRSV-PCV2-SIV clinical infection model 2-3-months post vaccination.\u003c/em\u003e Vaccine, 2009. \u003cstrong\u003e27\u003c/strong\u003e(7): p. 1002-7.\u003c/li\u003e\n\u003cli\u003eOpriessnig, T., et al., \u003cem\u003eEmergence of a novel mutant PCV2b variant associated with clinical PCVAD in two vaccinated pig farms in the U.S. concurrently infected with PPV2.\u003c/em\u003e Vet Microbiol, 2013. \u003cstrong\u003e163\u003c/strong\u003e(1-2): p. 177-83.\u003c/li\u003e\n\u003cli\u003eSeo, H.W., et al., \u003cem\u003eEffect of porcine circovirus type 2 (PCV2) vaccination on PCV2-viremic piglets after experimental PCV2 challenge.\u003c/em\u003e Vet Res, 2014. \u003cstrong\u003e45\u003c/strong\u003e(1): p. 13.\u003c/li\u003e\n\u003cli\u003eMartin-Valls, G.E., et al., \u003cem\u003eHigh levels of maternally derived antibodies do not significantly interfere with the development of humoral and cell-mediated responses to Porcine circovirus 2 after intradermal vaccination.\u003c/em\u003e Porcine Health Manag, 2023. \u003cstrong\u003e9\u003c/strong\u003e(1): p. 40.\u003c/li\u003e\n\u003cli\u003ePolo, J., et al., \u003cem\u003eHalf-life of porcine antibodies absorbed from a colostrum supplement containing porcine immunoglobulins.\u003c/em\u003e J Anim Sci, 2012. \u003cstrong\u003e90 Suppl 4\u003c/strong\u003e: p. 308-10.\u003c/li\u003e\n\u003cli\u003eMcKeown, N.E., et al., \u003cem\u003eEffects of porcine circovirus type 2 (PCV2) maternal antibodies on experimental infection of piglets with PCV2.\u003c/em\u003e Clin Diagn Lab Immunol, 2005. \u003cstrong\u003e12\u003c/strong\u003e(11): p. 1347-51.\u003c/li\u003e\n\u003cli\u003eFigueras-Gourgues, S., et al., \u003cem\u003eEffect of Porcine circovirus 2 (PCV-2) maternally derived antibodies on performance and PCV-2 viremia in vaccinated piglets under field conditions.\u003c/em\u003e Porcine Health Management, 2019. \u003cstrong\u003e5\u003c/strong\u003e(1): p. 21.\u003c/li\u003e\n\u003cli\u003eSibila, M., et al., \u003cem\u003eDescriptive analyses of maternally-derived antibody levels against porcine circovirus 2 (PCV-2) in 3- and 21-day-old piglets from farms of four European countries using different vaccination protocols in sows.\u003c/em\u003e Porcine Health Manag, 2022. \u003cstrong\u003e8\u003c/strong\u003e(1): p. 41.\u003c/li\u003e\n\u003cli\u003ePi\u0026ntilde;eiro, C., et al., \u003cem\u003eInfluence of sows\u0026apos; parity on performance and humoral immune response of the offspring.\u003c/em\u003e Porcine Health Manag, 2019. \u003cstrong\u003e5\u003c/strong\u003e: p. 1.\u003c/li\u003e\n\u003cli\u003eNuntapaitoon, M., et al., \u003cem\u003eImpact of parity and housing conditions on concentration of immunoglobulin G in sow colostrum.\u003c/em\u003e Trop Anim Health Prod, 2019. \u003cstrong\u003e51\u003c/strong\u003e(5): p. 1239-1246.\u003c/li\u003e\n\u003cli\u003eFenaux, M., et al., \u003cem\u003eImmunogenicity and pathogenicity of chimeric infectious DNA clones of pathogenic porcine circovirus type 2 (PCV2) and nonpathogenic PCV1 in weanling pigs.\u003c/em\u003e J Virol, 2003. \u003cstrong\u003e77\u003c/strong\u003e(20): p. 11232-43.\u003c/li\u003e\n\u003cli\u003eL\u0026oacute;pez-Lorenzo, G., et al., \u003cem\u003ePresence of Porcine Circovirus Type 2 in the Environment of Farm Facilities without Pigs in Long Term-Vaccinated Farrow-to-Wean Farms.\u003c/em\u003e Animals (Basel), 2022. \u003cstrong\u003e12\u003c/strong\u003e(24).\u003c/li\u003e\n\u003cli\u003ePileri, E., et al., \u003cem\u003eComparison of the immunoperoxidase monolayer assay and three commercial ELISAs for detection of antibodies against porcine circovirus type 2.\u003c/em\u003e Vet J, 2014. \u003cstrong\u003e201\u003c/strong\u003e(3): p. 429-32.\u003c/li\u003e\n\u003cli\u003eT\u0026oacute;thov\u0026aacute;, C., et al., \u003cem\u003eSerum protein electrophoretic pattern in piglets during the early postnatal period.\u003c/em\u003e Sci Rep, 2021. \u003cstrong\u003e11\u003c/strong\u003e(1): p. 17539.\u003c/li\u003e\n\u003cli\u003eSmith, P.K., et al., \u003cem\u003eMeasurement of protein using bicinchoninic acid.\u003c/em\u003e Anal Biochem, 1985. \u003cstrong\u003e150\u003c/strong\u003e(1): p. 76-85.\u003c/li\u003e\n\u003cli\u003eR Core Team, \u003cem\u003eR: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria.\u003c/em\u003e 2023.\u003c/li\u003e\n\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":"","lastPublishedDoi":"10.21203/rs.3.rs-4182328/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4182328/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePorcine circovirus type 2 (PCV2) is commonly associated with several clinical syndromes and diseases collectively referred to as porcine circovirus-associated disease, which has a significant economic impact on the global swine industry. In Japan, PCV2 is endemic to most pig farms, and vaccination for piglets and/or sows has been implemented on most farms. The present study explored factors associated with piglets at elevated risk of PCV2 infection. Pre-vaccination serum samples were collected, from birth through 19 days, from 39 piglets born to five sows; these specimens were used to measure the titer of maternally derived antibody (MDA) against PCV2, immunoglobulin G concentration, and total protein concentration. Additionally, records of sow parity and piglet body weights were examined.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eRegarding anti-PCV2 MDA, the mean maximum sample-to-positive (S/P) ratios among litters born from the five sows differed significantly (p \u0026lt; 0.001). The half-life of the anti-PCV2 MDA was estimated to be 17.4 days (95% confidence interval: 16.2–18.9 days). The trend to lower antibody titers appeared to be attenuated in piglets born from sows with higher parities. Furthermore, among litters from sows with a large number of parities, litters with larger mean birth weights exhibited greater variability in antibody titers. Additionally, within litters of piglets with higher mean birth weights, piglets with lower birth weights or lower serum total protein concentrations exhibited lower antibody titers.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe present study aimed to evaluate the relationship between serum anti-PCV2 MDA titers and several indicators in suckling piglets and to identify characteristics of piglets at elevated risk of PCV2 infection. In the field, indicators such as sow parity, birth weight, and serum total protein concentration may facilitate the identification of piglets at elevated risk of PCV2 infection.\u003c/p\u003e","manuscriptTitle":"Characterization of maternally derived antibody titers against porcine circovirus type 2 in serum of piglets and identification of piglets at elevated risk of infection","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-09 11:39:54","doi":"10.21203/rs.3.rs-4182328/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":"20db13a0-4f45-4ee5-909f-267486696663","owner":[],"postedDate":"April 9th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-05-14T04:24:01+00:00","versionOfRecord":[],"versionCreatedAt":"2024-04-09 11:39:54","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4182328","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4182328","identity":"rs-4182328","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}