一株新型三源重配H1N2亚型猪流感病毒的进化分析及对小鼠的感染性研究

Phylogeneticanalysis and infectivity in mice of a novel triple reassortant H1N2 Swine influenza virus

为了研究我国广西地区流行的猪流感病毒分子特征和感染性,本研究对分离自广西临床健康猪群中的H1N2亚型猪流感病毒(SIV)A/swine/Guangxi/238/2018(H1N2)(简称GX238株)进行了分子进化分析和致病性研究。扩增该病毒株8个基因节段后进行分子进化分析,结果显示其8个节段均与2015年~2016年在美国分离的H1N2亚型SIV有高度同源性(98.9%~99.7%),其中HA基因可能来自于2009年之前的人季节性H1N1亚型流感病毒,PB2、PB1、PA、NP、NA和NS可能来自北美三重配H1N2亚型SIV,M基因可能来自H1N1/2009。以106 EID50 SIV GX238株病毒鼻腔感染BALB/c小鼠后记录小鼠的体质量变化及死亡情况,感染后第3 d检测小鼠各脏器病毒复制情况。结果显示,感染组小鼠体质量与PBS对照组小鼠相比有明显下降趋势,感染小鼠40%死亡;在小鼠肺脏和鼻甲中病毒滴度分别达6.3 Log10EID50/mL、4.8 Log10EID50/mL,表明该病毒对小鼠表现出中等的致病力。本研究结果表明输入型SIV持续对我国猪群造成威胁,凸显了在世界范围内开展猪流感监测的必要性。

In order to investigate the molecular characteristics and the infectivity of prevalent swine influenza viruses(SIVs)in Guangxi province,molecular evolution analysis and pathogenicity of one H1N2 subtype swine influenza virus(SIV)A/swine/Guangxi/238/2018(GX238)isolated from apparently healthy pigs in Guangxi during the epidemiological surveillance were analyzed and evaluated in this study.Eight gene segments of this virus were amplified and further sequenced for molecular evolution analysis.The results demonstrated that the 8 genes of the virus had 98.9%-99.7%nucleotide identity with the influenza A(H1N2)viruses circulating in the U.S.swine population from 2015 to 2016.Phylogenetic analysis results suggested that the HA gene of the strain was derived from human seasonal influenza H1N1 viruses isolated before 2009,the NA gene was derived from the North American triple reassortant H1N2 SIV,and the internal genes were derived from the North American triplet H1N2(PB2,PB1,PA,NP,NS)and H1N1/2009(M).Two groups of mice(n=8)were intranasally inoculated with 106EID50 of GX238 virus and PBS for a negative control(mock),respectively.The weight and death of the experimental mice were observed and recorded.The replication of the virus were detected in the organs of the experimental mice on 3 days post infection.The group of mice inoculated with SIV showed a significant decrease compared with the control group during the observation period,and the mobility of mice of this group was 40%.The viruses were isolated in the samples of the nasal turbinates and lungs,with the titers of 6.3 Log10EID50/mL and 4.8 Log10EID50/mL,respectively,which showed its moderate pathogenicity in mice.The result highlighted the continuous threat of imported SIVs and sustained molecular surveillance program for swine influenza should be implemented worldwide.