2017-2019年贵州省BV系流感病毒的分子特征分析

Analysis of the molecular characteristics of influenza BV lineage viruses in Guizhou Province,2017-2019

目的了解贵州省BV系流感暴发疫情和重症病例毒株的分子特征,探讨其特异性分子靶标,为流感的防控提供依据。方法选取贵州省2017-2019年BV系流感暴发疫情、重症病例和普通流行毒株,经基因组的提取、HA和NA基因的扩增与测序,与参考株一起进行分子特征分析。结果贵州省所有毒株HA和NA基因进化树拓扑结构类似,整体上毒株处于3个分支,2017年的毒株聚集为一簇,2018年的分散存在,2019年的处于两个分支且相对较远,绝大部分暴发疫情毒株和重症病例毒株均处于分支1。贵州省所有毒株同疫苗株B/Colorado/06/2017 HA和NA基因同源性最高,分别为98.6%~99.3%和98.9%~99.4%;2017年BV系毒株间HA和NA基因同源性分别为99.9%和99.9%~100%,2018年分别为98.4%~99.3%和98.7%~99.1%,2019年分别为97.7%~100%和98.4%~99.9%,其中2019年分支2中的毒株间同源性分别为99.4%~100%和99.6%~99.9%,分支1中的分别为99.5%~100%和99.3%~99.9%,所有暴发疫情、重症病例毒株同当年度普通流行毒株之间同源性均高于99.4%;与疫苗株B/Colorado/06/2017相比所有毒株HA基因均存在S14N、G144D、V195I、K513R的突变,NA基因均存在Q371K、D490N的突变;2019年分支1中的毒株HA基因存在G148R、K151E和T563A以及NA基因存在A395T的特异性位点突变;分支2中的毒株HA基因存在V394I和NA基因存在V71A、K343E、A395V和V401I的特异性位点突变。同时,分支1中的毒株HA基因与疫苗株B/Brisbane/60/2008相比存在179-181KND的特异性缺失突变,与B/Colorado/06/2017相比存在181D的特异性缺失突变和150环的抗原位点突变。结论贵州省BV系暴发疫情毒株之间存在一定的差距,但暴发疫情毒株与普通流行毒株之间亲缘关系和同源性较高,2019年存在两个分支群系毒株的流行,且暴发疫情、重症病例毒株主要以分支1中的毒株流行为主;贵州省暴发疫情、重症病例毒株存在多个位点的特异性突变和缺失突变,应进一步加强分子特征的实时监测和致病力相关的特异性分子靶标研究。

This study aimed to understand the molecular characteristics and explore specific molecular targets of BV lineage strains involved in influenza epidemics and severe pneumonia cases in Guizhou province,to provide scientific evidence for influenza prevention and control.The BV lineage strains involved in influenza outbreaks,severe cases and common epidemics in Guizhou Province from 2017 to 2019 were examined.After genomic extraction,HA and NA gene amplification,and sequencing,the molecular characteristics of these strains together with reference strains were analyzed.The topological structure of the HA and NA evolutionary trees of all strains in Guizhou province was similar,and the strains formed three branches.In 2017,the strains were clustered,whereas in 2018,they were scattered.In 2019,they formed two relatively distant branches.Most of the outbreak strains and severe case strains were in branch 1.The sequence identity of HA and NA genes of all strains in Guizhou province was highest,at 98.6%-99.3%and 98.9%-99.4%,respectively.The sequence identity of HA and NA genes among BV lineage strains was 99.9%and 99.9%-100%,respectively,in 2017;98.4%-99.3%and 98.7%-99.1%,respectively,in 2018;and 97.7%-100%and 98.4%-99.9%,respectively,in 2019.In 2019,the sequence identity of the strains in branch 2 was 99.4%-100%and 99.6%-99.9%,respectively,and that in branch 1 was 99.5%-100%and 99.3%-99.9%,respectively.The sequence identity between the strains involved in all outbreaks and severe cases and the common epidemic strains in the current year was higher than 99.4%.Compared with those in vaccine strain B/Colorado/06/2017,all HA genes of the strains had mutations of S14N,G144D,V195I and K513R,and all NA genes had mutations of Q371K and D490N.The mutations G148R,K151E and T563A were found in the HA genes,and A395T was found in the NA genes of the strains in branch 1;V394I in HA genes and V71A,K343E,A395V and V401I in NA genes were found in the strains in branch 2.The HA genes of the strains in branch 1 had a 179-181KND deletion mutation,as compared with B/Brisbane/60/2008,and an 181D deletion mutation and 150 aera antigen locus mutation,as compared with B/Colorado/06/2017.In conclusion,a gap was observed among BV lineage strains in Guizhou province,but the genetic relationships and sequence identities were strong between BV lineage strains and common epidemic strains.Two cladistic strains were found in 2019,and the strains in branch 1 were the main strains involved in outbreaks and severe pneumonia cases.Further strengthening of real-time monitoring of molecular characteristics and further study of specific molecular targets related to the pathogenicity of BV lineage influenza virus are needed.