广州市人感染H7N9禽流感病毒高致病性变异株监测与基因进化分析

目的 通过对广州市人感染H7N9禽流感病毒高致病性变异株基因变异和进化特点进行分析,掌握本地区H7N9病毒病原学特点,为疾病防控提供参考。方法 选取2017年广州市人感染H7N9禽流感病毒阳性标本10份,提取核酸扩增HA、NA、M基因进行测序,通过生物信息学软件分析病毒重要蛋白突变情况和遗传进化特点。结果 广州地区H7N9禽流感病毒基因同源性差异较大,大部分毒株基因与广东毒株同源性最高,部分毒株基因与河南、内蒙古等地毒株同源性最高。监测到5株病毒为H7N9禽流感病毒高致病性变异株,部分病毒出现了HA蛋白Q226L的突变,提示对人呼吸道上皮细胞SAα-2, 6Gal受体结合能力增加。HA蛋白和NA蛋白上糖基化位点均有一定的增加和缺失突变。HA、NA和M1蛋白上毒力相关位点均突变增强。M2蛋白均呈现耐药突变,同时监测到2株高致病性突变株出现对神经氨酸酶抑制剂的耐药突变。遗传进化结果显示,HA基因和NA基因在华南和华东分支均有分布,M1基因进化特点相对复杂,分别与华南地区H9N2、H7N9病毒,及北方地区的H7N9病毒重组。结论 2017年广州地区发现2株对达菲耐药的人感染H7N9禽流感病毒高致病性变异株。H7N9禽流感病毒在广州地区不断发生进化重组,具有遗传多样性和复杂性,提示高致病性耐药株有向华南以外地区传播的风险。

Genetic variation and evolutionary characteristics of highly pathogenic avian influenza A(H7N9) viruses in Guangzhou,China

We analyzed the genetic variation and evolutionary characteristics of highly pathogenic avian influenza A(H7N9) viruses in Guangzhou. HA,NA and M genes were sequenced from 10 samples of H7N9 positive cases in Guangzhou in 2017. The highest homology of H7N9 genes were found with the genes of Guangdong viruses, the other genes were found with the genes of Henan and Inner Mongolia viruses. The molecular characteristics of highly pathogenic avian influenza were found in HA protein. Q226L mutations in HA protein of five strains were found, which suggested the increase of binding capacity to SA alpha-2, 6Gal receptors in human respiratory epithelial cells. The glycosylation sites were increased or deleted on HA and NA proteins. The virulence related proteins mutated of HA, NA and M1 proteins. All strains showed mutations of drug-resistant on M2 protein. Two strains also showed mutation of resistance to neuro ammonia inhibitors. The results of genetic evolution showed that HA and NA genes were distributed in Southern China and East China branches. But, the evolutionary characteristics of M1 gene were relatively complex. M1 genes were recombined with H9N2, H7N9 viruses in South China and H7N9 viruses in North China respectively. It is necessary to strengthen the continuous monitoring of avian influenza A(H7N9) viruses in Guangzhou.