Abstract: In order to study the epidemiology and genetic evolution characteristics of H9N2 subtype avain influenza virus (AIV) isolated from some areas of China, the hemagglutinin (HA) gene of 17 H9N2 subtype AIVs isolated from 2012 to 2015 were amplified by RT-PCR.Sequencing and phylogenetic analysis were performed, and the molecular characteristics of the motif of HA protein cleavage site, the receptor binding sites and potential glycosylation sites were analyzed.The results showed that the HA gene of 17 strains shared nucleotide and deduced amino acid homologies ranging from 87% to 100% and 75% to 100%, respectively.All strains belonged to Eurasian lineage, Y280-like sublineage.The cleavage sites motif of 17 isolates lacked multiple basic amino acids, which made them low pathogenic strains.There were amino acid variations at sites 149, 198, 234 and 235 of the receptor binding sites, while 16 isolates had a leucine residue at site 234, indicative of the characteristics of human influenza virus-like receptor.The analysis results of potential glycosylation site indicated that a glycosylation site deletion took place at amino acid site 218 of 11 isolates and site 492 of 4 isolates, while an additional potential glycosylation site were found at amino acid site 313 of 17 isolates.In summary, the epidemiological investigation of H9N2 subtype AIV should be enhanced and the difference between isolated virus and vaccine virus should be paid more attention.

Key words: H9N2 subtype avain influenza virus; HA gene; cloning; sequence analysis