杭州地区7株重排乙型流感病毒基因组特征分析

Genomic characterization of seven reassortant influenza B viruses in Hangzhou, China

目的研究杭州地区2014—2020年乙型流感流行情况并分析7株乙型流感病毒重排株遗传进化特征。方法收集2014年1月—2020年12月杭州地区流感样病例16 943例, 通过实时荧光定量PCR法检测乙型流感病毒, 使用特异性引物扩增阳性样本的8个基因片段(PB2、PB1、PA、HA、NP、NA、MP和NS)进行纳米孔三代测序并分析其遗传进化特征。结果 2014年1月—2020年12月杭州地区共鉴定了乙型流感病毒阳性样本1 090份, 总阳性率6.43%(1 090/16 943)。其中乙型Yamagata支系474份, 乙型Victoria支系616份。采用高通量测序获得乙型流感病毒全基因组228个, 发现7株乙型流感病毒重排株, 其中4株Yamagata系乙型流感病毒的NA基因与Victoria系乙型流感病毒重排, 2株Yamagata系乙型流感病毒(H644BY和H648BY)的NP和NA基因与Victoria系乙型流感病毒重排, 1株Victoria系乙型流感病毒的PB2、PB1、PA和NS基因与Yamagata系乙型流感病毒重排, 同时发现HA和NA基因存在多个抗原位点突变。结论 2014—2020年杭州地区乙型流感病毒出现多株罕见重排株, 具有潜在流行风险, 需改进传统检测方法并密切关注乙型流感病毒的变异重排情况及其与疫苗株的匹配度。

Objective To analyze the prevalence of influenza B virus in Hangzhou from 2014 to 2020 and the genetic evolution of seven reassortant strains of influenza B virus.Methods Influenza viruses were isolated from throat swabs collected from 16943 patients with influenza-like illness in Hangzhou from January 2014 to December 2020.The subtypes of influenza viruses were identified by real-time RT-PCR.Eight genes(PB2,PB1,PA,HA,NP,NA,MP and NS)of influenza B viruses were amplified with specific primers and then analyzed with nanopore sequencing and phylogenetic analysis.Results From January 2014 to December 2020,there were 1090 influenza B virus-positive samples,including 474 samples of Yamagata lineage and 616 samples of Victoria lineage,were identified in Hangzhou with an overall positive rate of 6.43%(1090/16943).Whole genomes of 228 strains of influenza B virus were obtained by nanopore sequencing and seven reassortant strains of influenza B virus were found.There were four reassortant influenza B viruses of Yamagata lineage with NA gene fragments from viruses of Victoria lineage,two strains of Yamagata lineage(H644_BY and H648_BY)with NP and NA gene fragments from Victoria lineage and one strain of Victoria lineage with PB2,PB1,PA and NS gene fragments from Yamagata lineage.Meanwhile,these seven strains possessed several mutations in the antigenic sites of HA and NA genes.Conclusions Several rare reassortant strains of influenza B virus with epidemic potential were detected in Hangzhou from 2014 to 2020,which indicated that the traditional detection methods should be improved and more attention should be paid to the reassortant influenza B viruses and the match between epidemic and vaccine strains.