两广地区2011-2012年H9N2亚型禽流感病毒的HA基因进化分析

Phylogenetic analysis of hemagglutinin genes of H9N2 subtype avian influenza viruses isolated in Guangdong and Guangxi provinces during 2011-2012

为探究两广地区H9N2亚型禽流感病毒（avianinfluenzavirus，AIV）的变异情况及分子流行规律，于2011-2012年从该地区发病鸡群中共分离到16株H9N2亚型A1V，并对分离株HA基因进行测序与进化分析。结果表明，分离株HA基因开放阅读框全长均为1683bp，编码560个氨基酸；HA基因核苷酸同源性为88．7％～99．6％，编码氨基酸同源性为91．8％～99．5％。本试验分离毒株与国内疫苗株（GD-SS、SH—F和SD-6）的核苷酸同源性在90．1％～92．6％之间，推导的氨基酸序列同源性在91．6％～94．8％之间。进化分析显示分离株可分为Group1和Group2两个亚分支，与疫苗株均属于欧亚谱系的Y280分支，但亲缘关系较远。分离株HA蛋白裂解位点附近序列有3种形式：PARSSR＋GLF、PSRSSR＋GLF和PARLSR0GLF，均无连续碱性氨基酸的插A，符合低致病性AIv的特征。本试验发现分离株GD4、GX2在HA1的127、295位分别增加一个潜在的糖基化位点；除分离株GD5和GD6外，其余分离株在HAl的216位发生Q216L氨基酸突变，表明其存在感染人的可能性。

Sixteen H9N2 subtype avian influenza virus（AIV） were isolated from Unhealthy chicken flocks in Guangdong and Guangxi provinces during 2011--2012. The hemagglutinin （HA） genes were amplified and cloned into the pMD19-T vector （TaKaRa） followed by sequencing for three times. The DNA sequences were analyzed using DNAStar （version 7）. The results showed that the open reading frame （ORF） of the 1 6 HA genes contained 1 6 mino acids. The HA genes of 16 H9N2 AIV isolates shared 88.7 and 91.8%-99. 5% deduced amino acid homology. Nucleotide an nucleotides coding for 560 a- -99.6% nucleotide homology deduced amino acid sequence homologies between all H9N2 AIV isolates and the domestic vaccine strains ranged from 90.1%- 92.6% and 91.6%-94.8% ,respectively. Phylogenetic analysis indicated that all the strains could be divided into Group 1 and Group 2 and that all isolates together with the vaccine strains belong to Y280 sublineage in Eurasian lineage. In the cleavage sites of HA protein, all 16 strains had 3 kinds forms： PARSSR ↓ GLF,PSRSSR ↓GLF,and PARLSR ↓ GLF, which met the characteristic of low-pathogenic avian influenza. The GD4 and GX2 had an extra potential glycosylation site at 127,295, respectively, compared with the other isolated strains and the vaccine strains. Further- more, 14 out of the 16 isolates showed mutations at Q216L, which indicated that the viruses might have the potential to cross species to infect humans.