Genetic characterization and pathotypical analysis of two strains of pigeon Newcastle disease virus of Jiangsu in China

Pigeon Newcastle disease (ND) is a severe infectious disease caused by pigeon Newcastle disease virus (NDV) or Paramyxovirus type 1 (PPMV-1). Genotype VI NDV is a major cause of ND in Columbiformes (i.e. pigeons and doves). In this study, two strains of NDV (Pigeon/China/JS/VI-NJ/2006 and Pigeon/China/JS/VI-HZ/2017) were isolated from diseased pigeons. The virus particles were about 120 nm observed under the transmission electron microscope. The MDT and ICPI values of the two viruses were typically mesogenic. The amino acid sequence at cleavage site of F protein of Pigeon/China/VI-NJ/2006 and Pigeon/China/VI-HZ/2017 strains were 112 RRQKRF 117 and 112 KRQKRF 117 , with the molecular characteristics of virulent strains. The whole genome homology analysis showed that the two strains had high homology with strains of genotype VI (92.52%~99.13%). Furthermore, based on the phylogenetic tree of the F gene, Pigeon/China/VI-NJ/2006 and Pigeon/China/VI-HZ/2017 were closely related to the sub-genotype VI 2.1.1.2.1 and VI.2.2.2, respectively. The comparison of the amino acid positions of the F and HN proteins from Pigeon/China/JS/VI-HZ/2017 strain showed that there were four mutant sites (20, 22, 235, 514) on the F protein and four mutant sites (253, 280, 288, 326) on the HN protein, demonstrating that genetic variation had occurred. The survival rate of pigeons infected with the two strains were 40% and 20%, with lesions in multiple tissues, indicating that these strains had strong ability to spread and high pathogenicity. In summary, the results showed that the prevalence of genotype VI NDV was contributed by strains from diverse sub-genotypes, suggesting the importance of pigeon NDV surveillance in China.