[Comparison of sequences of the hemagglutinin gene and phylogenetical analysis of H9 subtype avian influenza viruses isolated from some regions in China]

Abstract

In order to explore the genetic mutaions of the hemagglutinin(HA) gene and the law of molecular epidemiology of H9 subtype avian influenza viruses in China, 23 H9 subtype avian influenza viruses(AIVs) were isolated from 12 provinces of China in recent years. Their nucleotide sequences of cDNA of HA gene were determined by RT-PCR and sequencing. Their nucleotide and putaive amino acid sequences homology was compared. The results showed that their nucleotide sequence homology was from 94.1% to 100% and that amino acid sequence homology was 95.4% to 100%. The sequences of the HA gene of these isolates were analyzed and compared with that of another 8 isolates from reference. The similedty indicated that HK170499 isolated from Hong Kong was close to the 2 isolates of Japan. And of the 31 isolates with complete HA gene sequences there were 5 isolates, HA gene of which were loss of one potelltial glycosylation site, which were CKGS199, CKTJ196, CKT296, CKSH300 and CKBJ197. Then 1098 nucleotide regions (bases 55 to 1,152) of HA gene of 23 isolates in this study were analyzed phylogenetically and compared with sequences from 31 H9 subtype viruses available in the GenBank database. Although considerable variation at the cleavage sites of the different viruses was observed, giving 10 different amino acid motits, none had multiple basic amino acids that correlate with highly pathogenic avian influenza (HPAI) isolates. Examination of amino acid sequences involved in repeptor binding site(RBS) revealed that the amino acid residue at position 191 characteristically distributed in the 54 isolates, that is, this amino acid residue of the isolates of mainland China and several Hong Kong strains was Asn(N) and that of the others was His(H). And the 141 143 amino acid residues, involved in forming the potential glycosylation sites, had the similary characteristic distribution with the 191aa position. The isolates with Asn-191. excluding CKBJ197, had NVS in the position 141aa143aa, meanwhile those with His-191 had NVT. Twenty-six mainland China isolates was genetically in Eurasian lineage but did not show distinctly geographical and temporal relationship. It is concluded that in recent years H9N2 subtype AIV, circulating in chicken flocks of mainland China, may have a common origini. These findings provides importan basis for establishment of scientifically preventive measurements to control H9 subtype avian influenza.