长沙市1例人感染H5N6禽流感病毒遗传进化和基因特征

Analysis of the genetic evolution and gene characteristics of H5N6 avian influenza virus in a human infection case in Changsha City

目的 对长沙市1例人感染禽流感H5N6病毒A/Changsha/1/2022(H5N6)的遗传进化与分子特征进行分析,为防控人感染H5N6禽流感提供依据。方法 运用第三代测序平台对样本进行全基因组测序,从美国国家生物技术信息中心(National Center for Biotechnology Information, NCBI)和全球共享禽流感数据倡议组织(Global Initiative on Sharing All Influenza Data, GISAID)数据库下载参考序列进行比对,利用Mega7软件构建遗传进化树并分析关键氨基酸变异位点。结果 对序列进行分析发现,本研究毒株属于H5亚型Clade2.3.4.4b分支。PB1与湖南省A/duck/Hunan/S40199/2021(H5N6)同源性为99.69%;PB2与A/Whooper swan/Sanmenxia/Y36/2020(H5N8)同源性为98.58%;其余序列与2021年广州发现的毒株A/Guangdong/1/2021(H5N6)高度同源。以上结果表明该病例是由重组的H5N6亚型禽流感病毒感染导致。对毒株序列的氨基酸位点分析发现,裂解位点氨基酸组成为RERRRKR↓GLF,符合高致病性禽流感特征。HA序列中Q226L和G228S位点未发生突变,提示病毒保留结合禽类受体的特征,然而S127P、S137A、T160A、T192R、A267T的突变增加了病毒对人类的亲和性。NA蛋白茎部59-70位点缺失,提示该毒株能增强病毒在哺乳动物体内的毒力。内部基因PB1发生S622G突变,PB2发生K389R和V598T突变,PA发生N409S突变,M1发生N30D和T215A突变,NS1发生P42S突变,这些突变会增强禽流感病毒感染小鼠的毒力。结论 本研究的长沙市人感染H5N6病毒为高致病性禽流感病毒,倾向于结合禽类受体,但关键氨基酸位点存在多处变异进而易于感染人类,应持续加强对禽流感H5N6病毒的监测与研究。

Objective To analyze the genetic evolution and molecular characteristics of the H5N6 avian influenza virus A/Changsha/1/2022(H5N6)in a human infection case in Changsha City,providing insights for the prevention and control of H5N6 avian influenza transmission to humans.Methods The sample underwent whole-genome sequencing on a third-generation sequencing platform.Reference sequences were downloaded from the NCBI and GISAID databases for comparison.The phylogenetic tree was constructed and key amino acid mutation sites were analyzed using MEGA7 software.Results The sequence analysis results revealed that the strain studied belongs to the H5 subtype Clade 2.3.4.4b branch.The PB1 gene shared 99.69%homology with the H5N6 virus A/duck/Hunan/S40199/2021(H5N6)from Hunan Province;PB2 had 98.58%homology with A/Whooper swan/Sanmenxia/Y36/2020(H5N8);and other sequences showed high homology with the strain A/Guangdong/1/2021(H5N6)discovered in Guangzhou in 2021.These results indicate that an infection with a recombinant H5N6 subtype avian influenza virus caused the case.The amino acid composition of the cleavage site was RERRRKR↓GLF,consistent with high-pathogenicity avian influenza characteristics.The HA sequence showed no mutations at the Q226L and G228S sites,indicating the preservation of characteristics binding to avian receptors.However,mutations at the S127P,S137A,T160A,T192R,and A267T sites increased the virus's affinity for humans.A deletion found in positions 59-70 of the NA protein stalk implies enhanced viral virulence in mammals.Mutations were noted in the internal genes;S622G in PB1,K389R and V598T in PB2,N409S in PA,N30D and T215A in M1,and P42S in NS1,which may enhance the virulence of avian influenza virus in infecting mice.Conclusions The H5N6 virus strain detected in a human case in Changsha City in this study is highly pathogenic,prone to bind to avian receptors,but numerous mutations at key amino acid sites facilitate infection in humans.Continuous monitoring and research on H5N6 avian influenza virus should be strengthened.