RESUMEN
In order to explore the genetic mutations of the H9N2 subtype avian influenza viruses isolated in Shandong, sixteen avian influenza virus subtype H9N2 were isolated from different areas of Shandong Province. The complete HA fragments of the viruses were amplified by RT-PCR and the sequences were analyzed on homology and heredity evolution after the cloning and sequencing of the products. The results showed that the amino acid motif of cleavage sites for all the sixteen virus in the HA gene were RSSR decrease GLF, which was consistent with the characterization of the LPAIV. Seven to nine potential glycosylation sites were found during the analysis and the receptor binding sites were relatively conservative except the 198 site. The Leucine(L) at the amino acid position 234 in the HA genes of all isolates indicated the potential of binding with SAalpha,2-6 receptor of mammals. Homology analysis showed that the homology of HA nucleotide and amino acid sequences was 96.3%-99.9% and 97.1%-99.6% for different strains. They belonged to a branch of the A/Duck/Hong Kong/Y280/97 in the phylogenetic tree.