杭州地区2014—2019年乙型流感病毒HA和NA基因遗传进化分析

Genetic evolution of influenza B virus hemagglutinin(HA)and neuraminidase(NA)genes in Hangzhou between 2014 and 2019

目的研究2014—2019年杭州地区乙型流感病毒的流行情况以及血凝素基因(HA)和神经氨酸酶基因(NA)的遗传进化特征。方法收集2014年10月—2019年9月间杭州地区流感样病例10481例,用实时RT-PCR法检测乙型流感病毒,同时选取部分乙型流感病毒阳性样本,用特异性引物扩增HA和NA基因,进行基因测序并分析其遗传进化特征。结果发现自2014年以来,杭州地区每年都有乙型流感病毒的流行。其中5~14岁年龄段人群发病率最高。2014—2019年,杭州地区流行的Victoria系乙型流感病毒都属于V1A进化簇,而Yamagata系乙型流感病毒都属于Y3进化簇。HA和NA基因的序列一致性分别为94.67%~100.00%和97.13%~100.00%,并在多个抗原位点发生了改变,同时出现了重排株。结论乙型流感病毒在杭州地区流感流行中影响显著。2014—2019年,杭州地区乙型流感病毒出现了抗原变异和基因重排,流行株和疫苗株之间存在不匹配的情况,但目前并未发现耐药株的出现和流行。

Objective To analyze the prevalence of influenza B virus in Hangzhou between 2014 and 2019,and the variation in hemagglutinin(HA)and neuraminidase(NA)genes.Methods Viruses were isolated from throat swabs collected from 10481 patients with influenza-like illness in Hangzhou from October 2014 to September 2019.The subtypes of influenza viruses were identified by real-time RT-PCR.HA and NA genes of some influenza B virus strains were amplified with specific primers and then analyzed with gene sequencing and phylogenetic analysis.Results Influenza B virus had circulated in Hangzhou every year since 2014 and caused a much higher morbidity in people aged 5-14 years.The Victoria lineage of influenza B virus circulating in Hangzhou between 2014 and 2019 belonged to the V1A clade,while the Yamagata lineage belonged to the Y3 clade.Homology analysis showed that 124 strains shared 94.67%-100.00%homology in HA gene sequences and 128 strains shared 97.13%-100.00%homology in NA gene sequences.Influenza B virus possessed several mutations in the antigenic sites of HA and NA.Conclusions Influenza B virus played a critical role in the influenza epidemics in Hangzhou.During 2014 to 2019,genetic mutations in the antigenic sites of HA and NA and reassortant strains were detected,and there was a mismatch between epidemic and vaccine strains.However,no drug-resistant virus was found.