南通市2022—2023年流感H3N2亚型分子进化特征

Molecular evolutionary characteristics of H3N2 subtype influenza virus in Nantong City from 2022 to 2023

目的了解近年南通市流感暴发疫情中H3N2流感病毒的分子进化特征。方法采集2022—2023流感监测年南通市流感暴发疫情中患者鼻咽拭子样品,运用RT-qPCR进行核酸检测,将Ct值<30的样品进行病毒分离,分离的H3N2病毒株构建文库后进行高通量测序分析,对HA、NA基因进行核苷酸和氨基酸相似度分析并构建系统进化树。结果共报告23起流感暴发疫情,均为甲型流感病毒,H3N2亚型12起(占52.17%)和H1N1型11起(占47.83%)。测序10株H3N2型毒株,HA、NA基因的核苷酸同源性为96.59%~100.00%、98.58%~100.00%,氨基酸同源性为96.13%~100.00%、96.40%~100.00%;与WHO推荐的北半球疫苗株A/Darwin/9/2021相比,HA、NA基因的核苷酸同源性为96.62%~97.38%、96.87%~97.36%,氨基酸同源性为96.86%~97.21%、94.58%~96.67%。HA基因发生的重要氨基酸突变有I156K,K187N,I208F,G241D;RBS位点均未发生突变;NA基因发生的重要突变有S331G,S150R/H;神经氨酸酶抑制剂(NAI)作用位点保守。系统发育分析显示,10株H3N2型分成2a.3和3C.2a1b.2b两个进化分支,与疫苗株的匹配性较好。结论H3N2流感病毒持续进化,应加强监测,掌握流感病毒的基因进化特征,为精准防控提供科学依据。

Objective To investigate the molecular evolutionary characteristics of H3N2 subtype influenza virus during influenza outbreaks in Nantong City in recent years.Methods Nasopharyngeal swab specimens were collected from influenza patients in Nantong City during influenza outbreaks from 2022 to 2023,and quantitative real-timePCR(qPCR)assay was performed test influenza virus nuclear acid.Viruses were isolated from specimens with Ct values of<30,and the H3N2 virus isolates were subjected to high-throughput sequencing.Nucleotide and amino acid sequence alignments of HA and NA genes were performed,and phylogenetic trees were created.Results A total of 23 influenza outbreaks were reported,and all were caused by influenza A virus,including 12 outbreaks caused by H3N2 virus(52.17%)and 11 outbreaks caused by H1N1 virus(47.83%).Sequencing of 10 H3N2 virus isolates showed that the nucleotide sequence homology of HA and NA genes was 96.59%to 100.00%and 98.58%to 100.00%and the amino acid sequence homology was 96.13%to 100.00%and 96.40%to 100.00%,respectively.The nucleotide sequence homology of HA and NA genes was 96.62%to 97.38%and 96.87%to 97.36%and the amino acid sequence homology was 96.86%to 97.21%and 94.58%to 96.67%as compared to the influenza vaccine candidate A/Darwin/9/2021 recommended for use in the northern hemisphere by WHO.The major amino acid mutations in the HA gene included I156K,K187N,I208Fand G241D,with no mutations seen in RBS sites,and the major amino acid mutations in the NA gene included S331G and S150R/H,with conserved sites of action of neuraminidase inhibitors.Phylogenetic analysis revealed that 10 H3N2 virus isolates were clustered into 2a.3 and 3C.2a1b.2b clades,which matched highly to the vaccine isolate.Conclusions H3N2 virus continues to evolve.Intensified surveillance is required to understand the evolutionary characteristics of influenza virus genes,so as to provide insights into precision containment of influenza.