[Genome sequencing and phylogenetic analysis of avian influenza viruses subtype H9N2].

Samples of chicken, duck, quail, and pigeon were collected from Jiangsu, Anhui, and Hebei in 2009-2011, and sixteen H9N2 subtype isolates of avian influenza virus (AIV) were identified. The eight full-length genes of 16 AIV isolates were amplified by RT-PCR and sequenced. Genome sequence analysis showed that the amino acid motif of cleavage sites in the HA gene was P-S-R/K-S-S-R, which was consistent with the characterization of the LPAIV, and the Leucine (L) at the amino acid position 226 in the HA genes of all isolates indicated the potential of binding with SAalpha, 2-6 receptor. All isolates had a S to N substitution at residue 31 in the M2 gene, which is related to the resistance phenotype of adamantanes. The key molecular features of 16 AIV isolates from different hosts were same. Genome phylogenetic analysis revealed that all 16 H9N2 subtype AIVs originated from F98-like virus as backbone and formed two new genotypes through reassortment with HA gene of Y280-like virus and PB2 and M genes of G1-like virus. Our findings suggest that more attention should be paid to the surveillance of H9N2 influenza virus and its direction of reassortment.