2011年－2014年我国部分省区 H9N2亚型禽流感病毒HA 基因序列分析

摘要

本研究于2011年－2014年在我国部分省区鸡群中鉴定出49株 H9N2亚型禽流感病毒,并对所有毒株的 HA 基因进行克隆、测序及序列分析。结果表明,49个毒株的 HA 基因开放阅读框全长均为1683 bp,编码560个氨基酸。所有分离株均属于以 HK/Y280/97株为代表的 H9．4．2谱系,并明显分成2个亚分支(H9．4．2．5和 H9．4．2．6)。分离株 HA 基因核苷酸同源性在87．1％~100％之间,与疫苗株 SH/F/98株、GD/SS/94株和 SD/6/96株核苷酸同源性在89．4％~92．5％之间。对 HA 基因的推导氨基酸序列分析表明,所有分离株裂解位点附近没有连续的碱性氨基酸插入,符合低致病力毒株特征,受体结合位点为PWTN∗LY 形式,受体结合位点左沿为 NGLM/QGL 形式,右沿均为 GTSKA 形式。在49个分离株中共发现10个潜在糖基化位点,但只有6个糖基化位点保守。研究表明,近年来 H9N2亚型禽流感在我国多个地区流行,2013年以后流行毒株趋势以 H9．4．2．5为主,但病毒基因仍在不断发生变异,因此需要继续加强对H9N2亚型禽流感分子流行病学的监控。%In this study,49 H9N2 subtype avian influenza virus strains (AIVs)were collected from sick chickens in China during 201 1-2014.The HA genes of these virus were sequenced and the sequence were analyzed.The results showed that the open reading frame of all the HA genes contained 1 683 nucleotides coding for 560 amino acids.Phylogenetic analysis based on the HA genes showed that the 49 isolates be-longed to H9.4.2 lineage with the strain HK/Y280/97 as representative,and they were obviously clustered into two sub-lineages (H9.4.2.5 and H9.4.2.6 ).The HA gene homology of all the sequences were in 87.1%-100%.The nucleotide identity of the 49 virus strains with the vaccine strains of H9N2 AIV (SH/F/98,GD/SS/94,and SD/6/96)were between 89.4%-92.5%.Analysis of the cleavage site of the deduced HA amino acid sequences of the 49 isolates showed there were no polybasic residues,which met the char-acteristics of low-pathogenic avian influenza virus.The tested strains in this study had the receptor binding site motifs as PWTN∗LY.They had motifs NGLM/QGL on the left-edge of receptor-binding pocket,and GTSKA on the right-edge.The results showed that the strains carried potential glycosylation sites that were located at ten different amino acid positions,but only six of them were conservative.In the present study,our findings demonstrated the continued circulation of H9N2 AIVs in China and showed the H9.4. 2.5 sub-lineage viruses were prevalent strains since 2013.As variations of H9N2 genes were still found, continuing molecular epidemiological surveillance of H9N2 AIVs in China is necessary.