Complete genome and molecular characterization of genotype VII velogenic Newcastle disease virus isolated in China.

Circulation of dominant genotype VII of Newcastle disease virus (NDV) causes significant economic losses to the poultry industry in China. Although most of genotype VII NDV has frequently been isolated in China to date, the genome sequence difference between duck-origin and chicken-origin NDVs remains largely unknown. In this study, a NDV strain of Chicken/China/HB/2017 (HB), isolated during an outbreak in China, was subjected to genetic, biological, phylogenetic and the pathogenicity characterization. The complete genome of HB strain is 15,192 nucleotides (nt) long and consisting of six genes in the order of 3'-NP-P-M-F-HN-L-5'. Several amino acid mutations were identified in the functional domains of F and HN proteins, including fusion peptide, heptad repeat region, transmembrane domains, and neutralizing epitopes. Phylogenetic analysis based on the F gene revealed that the HB strain and three other duck-origin NDV strains in China were grouped under subgenotype VII.1.1 and shared 99.1~99.2% nucleotide identity. Additionally, the challenge experiment results showed that the strain was highly pathogenic with 100% morbidity and mortality. Virus shedding was detected from 2 days post-infection until the fifth day. In conclusion, this study offers our understanding of circulating strains of NDV and genes involved in virulence and evolution between different hosts. Keywords: Newcastle disease virus; China; complete genome; genotype VII; mutations.