Characterization and phylogenetic analysis of H9N2 subtype avian influenza viruses isolated from eastern China

The biological properties of six chicken-origin H9N2 subtype avian influenza viruses(AIVs) isolated from eastern China were characterized and the molecular phylogenetic analysis of HA and NA genes was made.All these viruses were non-pathogenic to SPF chicken with IVPI scores of 0,and grouped into two subgroups by monoclonal antibody of 4E7 with hemagglutination inhibition(HI) test.The sequence analysis of HA gene showed that the amino acid sequence in HA cleavage motif was RSSR↓GLF in all six strains,and the amino acid residues of potential glycosylation sites in isolates of Ck/HD/16/07 and Ck/HD/112/05 were different from those of other four isolates.The sequence analysis of NA genes indicated that NA gene was assigned to N2 subtype,and NA gene in four isolates deleted three amino acid residues in the stalk,whereas there was no deletion in other two isolates.