中文摘要：

为了解中国目前H9N2亚型禽流感病毒（avian influenza virus,AIV）血凝素（HA）基因的遗传变异情况,对中国不同地区分离的10株H9N2亚型AIV的HA基因进行扩增、克隆和测序,并对所获得的HA全序列进行同源性和遗传进化分析。结果表明,10个分离株的裂解位点均为RSSR↓GLF,符合低致病性AIV的分子特征;10个分离株有7～9个潜在糖基化位点,由于基因突变有些HA基因出现了新的糖基化位点;与参考株相比,发现了4个抗原表位的突变,这些表位的突变可能引起病毒致病性的改变;受体结合位点除198位有变异外,其他位点均较保守;6株病毒234位氨基酸均为L,具有与哺乳动物唾液酸α,2-6受体结合的特征;10个分离株HA基因与国内疫苗株的核苷酸及氨基酸序列同源性分别为90.4%～99.2%和92.2%～98.7%;10个分离株同属于欧亚谱系中的A/duck/Hong Kong/Y280/97群,但差异显著,为此本试验又将其分为4个不同的亚群。人工感染排毒试验结果表明,BJ15和NJ17分离株在鸡体内具有较强的复制能力,排毒周期较长且排毒量也较大,而S145N的漂变导致在145—147位氨基酸多出1个糖基化位点NGT,可能是分离株复制能力增强的原因。

英文摘要：

In order to explore the genetic mutations of the H9N2 subtype avian influenza viruses isolated in China, the complete HA segments of the ten H9N2 subtype avian influenza viruses were amplified by PCR and the sequences were analyzed on homology and heredity evolution. The results showed that the amino acid motif of cleavage sites for all the ten viruses in the HA genes were RSSR ~ GLF, which was consistent with the characterization of the low pathogenic avian influenza virus. 7 to 9 potential glycosylation sites were found in the HA genes and 4 mutations were found in the antigen epitope region of the HA genes of the viruses. The receptor binding sites were relatively conservative except that of 198 site and the leucine at the amino acid position 234 in the HA genes of six isolates indicated the potential of binding with SAa, 2-6 receptor of mammals. The re- sults indicated that the HA genes of the 10 viruses and the vaccine strains displayed nucleotide homologies ranging from 90.4 % to 99.2% and amino acid homologies ranging from 92.2% to 98.7%, respectively. They belonged to a branch of the A/duck/ Hong Kong/Y280/97 in the phylogenetic tree. The SPF chickens infected respectively by BJ15 and NJ17 isolates shed more vi- rus and last for a longer time. The new occurring potential glycoprotein site NGT in the HA protein of BJ15 and NJ17 isolates might cause the enhancing pathogenicity.