The phylogenetic analysis and molecular characterization of H9N2 avian influenza viruses isolated in Jiangsu province from 2014 to 2016

H9N2 avian influenza virus (AIV) circulates widely in China, causing a large economic loss to poultry industry and posing a big potential threat to public health. From 2014 to 2016, the positive ratio of H9N2 AIV isolation from chicken in the living market of Jiangsu province is 8.39%–13.74%. Ten H9N2 virus isolates were selected for whole genome sequencing and phylogenetic analysis. The result demonstrated that the HAs of those H9N2 virus isolates belonged to the same lineage and had a high homology with earlier Jiangsu isolates. In contrast, NA genes of those isolates evolved far away from the earlier Jiangsu isolates. Compared to earlier isolates, the nucleotide homology of NA genes and amino acid homology of NA protein were ranged from 91.4% to 93.9% and 91.2% to 93.8%, respectively. All those H9N2 viruses belonged to genotype B69 which predominates at present in China. The result of MegAlign analysis showed that 226 site in the hemagglutinins of those H9N2 isolates were Leucine. Further, it was proved that those H9N2 virus isolates preferred to bind to human type α2,6 sialic acid receptor in solid-phase receptor binding assay.