2021年武汉市乙型流感病毒监测及序列进化分析

Epidemiological and evolutionary analyses of influenza B virus in Wuhan,2021

目的分析武汉市2021年分离乙型流感病毒基因组变异情况及分子进化特征。方法采集2021年武汉市流感样病例咽拭子标本,进行核酸检测、病毒分离,选取34株乙型流感病毒代表毒株进行全基因组测序,利用生物信息学软件构建进化树并分析分子进化特征。结果2021年武汉市共监测病例标本2242例,流感病毒核酸检测阳性218例,均为乙型流感病毒Victoria系(Influenza B virus Lineage Victoria,BV),阳性率9.72%。2021年武汉分离的BV系流感病毒与疫苗株比,HA基因同源性为98.65%-99.24%,NA基因同源性为98.89%-99.54%。2021年武汉分离的BV系流感病毒归属于V1A.3a.1和V1A.3a.2分支,V1A.3a.2为2021年武汉市优势株。发现多处关键抗原表位发生了变异,未发现耐药位点变异。结论2021年武汉分离的BV系流感病毒较疫苗株均存在数个抗原位点变异,因此应加强对病毒变异的持续监测,为疫苗株更新、流感防控及临床诊疗措施的制定提供参考。

Objective To analyze the variation and evolution characteristics of influenza B virus in Wuhan in 2021.Methods Throat swab specimens were collected from influenza-like cases in Wuhan sentinel hospitals in 2021.After virus isolation,complete genomes of 34 influenza B strains were sequenced using illumina Miseq sequencer,and the sequences were assembled using CLC Genomic Workbench v.21,B/Washington/02/2019 as references.Phylogenetic trees were calculated with the maximum likelihood(ML)method using the nucleotide substitution model with the lowest Bayesian information criterion scores,as identified for each alignment in the MegaX software.Results In 2021,a total of 2242 throat swabs were collected from influenza-like cases,218(9.72%)of them were positive for influenza virus,and all of latter were influenza B virus strains of Victoria lineages(BV).The isolated influenza B strains shared 98.65%-99.24%homology with the vaccine strain in HA gene,and 98.89%-99.54%in NA gene.Clade V1A.3a.2 was the dominant strain in Wuhan in 2021.Several key variations,such as R133G,N150K,N197D,were found in HA antigenic site,yet no mutation was found in the site related to drug resistance in NA.Conclusion Compared with the WHO vaccine strains,the BV influenza viruses isolated in Wuhan in 2021 had several antigenic site variations.Therefore,genome of influenza virus should be monitored continuously to provide reference for vaccine strain update,influenza prevention and control,and formulation of clinical diagnosis and treatment measures.