贵州省2014-2017年H7N9禽流感病毒HA和NA基因特征分析

Genetic characteristics of hemagglutinin and neuraminidase of avian influenza A （H7N9） virus in Guizhou province, 2014-2017

目的 分析2014－2017年贵州省H7N9禽流感病毒HA和NA基因的分子特征和感染风险。方法 对2014－2017年贵州省获取的18例确诊人感染H7N9病例和6份环境样本分离的H7N9病毒株的HA和NA基因进行扩增，运用生物信息学软件解析其变异和遗传进化。结果 2014－2015年贵州省2株毒株与WHO推荐的A/Shanghai/2/2013和A/Anhui/1/2013疫苗株HA和NA基因的同源性最高，分别为98.8%～99.2%和99.2%；2016年2株和2017年14株与A/Hunan/02650/2016疫苗株同源性最高，分别为98.2%～99.3%和97.6%～98.8%；2017年其余6株与A/Guangdong/17SF003/2016疫苗株同源性最高，为99.1%～99.4%和98.9%～99.3%。所有毒株均属于长江三角洲分支，但主要聚集为3个次分支。2017年贵州省西部有6株毒株（含2例人感染病例毒株）裂解位点存在插入突变为PEVPKRKRTAR↓GLF，具备高致病性禽流感病毒的分子特征；受体结合关键位点存在A134V、G186V和Q226L突变，NA蛋白颈区“QISNT”均缺失，毒株A/Guizhou-Danzhai/18980/2017发生耐药突变R294K，9株毒株NA蛋白糖基化位点发生NCS42NCT突变。结论 2014－2017年贵州省H7N9禽流感病毒HA和NA基因存在遗传差异，关键位点的变异增强了病毒对人体的易感性和毒力，部分毒株发生耐药突变，其感染与致病风险增加。

Objective To understand the molecular characteristics of hemagglutinin （HA） and neuraminidase （NA） as well as the disease risk of influenza virus A H7N9 in Guizhou province. Methods RNAs were extracted and sequenced from HA and NA genes of H7N9 virus strains obtained from 18 cases of human infection with H7N9 virus and 6 environmental swabs in Guizhou province during 2014-2017. Then the variation and the genetic evolution of the virus were analyzed by using a series of bioinformatics software package. Results Homology analysis of HA and NA genes revealed that 2 strains detected during 2014-2015 shared 98.8%-99.2% and 99.2% similarities with vaccine strains A/Shanghai/2/2013 and A/Anhui/1/2013 recommended by WHO, respectively. Two strains detected in 2016 and 14 strains detected in 2017 shared 98.2%-99.3% and 97.6%-98.8% similarities with vaccine strain A/Hunan/02650/2016, respectively. Other 6 stains detected in 2017 shared 99.1%-99.4% and 98.9%-99.3% similarities with strain A/Guangdong/17SF003/2016, respectively. Phylogenetic analysis showed that all the strains were directly evolved in the Yangtze River Delta evolution branch, but they were derived from different small branch. PEVPKRKRTAR↓GLF was found in 6 of 24 strains cleavage site sequences of HA protein, indicating the characteristic of highly pathogenic avian influenza virus. Mutations A134V, G186V and Q226L at the receptor binding sites were found in the HA. All the strains had a stalk deletion of 5 amino acid residue ＂QISNT＂ in NA protein, and drug resistance mutation R294K occurred in strain A/Guizhou-Danzhai/18980/2017. In addition, potential glycosylation motifs mutations NCS42NCT were found in the NA of 9 of 24 strains. Conclusions HA and NA genes of avian influenza A （H7N9） virus showed genetic divergence in Guizhou province during 2014-2017. The mutations of key sites might enhance the virulence of the virus, human beings are more susceptible to it. Hence, the risk of infection is increasing.