一株重配型H1N2猪流感病毒的进化分析及对小鼠的致病性

Phylogenetic Analysis and Pathogenesis in Mice of a Novel Reassortant H1N2 Subtype Swine Influenza Virus

为了进一步了解我国辽宁省猪流感(SI)的流行情况及病原的进化规律,对2016年年末在辽宁省某生猪屠宰场进行SI病原学监测时分离到的一株H1N2亚型猪流感病毒(SIV)A/swine/Liaoning/FX575/2016(简称FX575)进行全基因组序列测定,通过对其8个基因片段的基因来源进行分析,确定基因型;构建系统进化树;分析相关分子特征;进一步以6周龄雌性BALB/c小鼠为感染模型,通过测定感染后小鼠的体重变化和脏器病毒含量评估病毒的致病性。结果显示:FX575为一株三重重配型的H1N2病毒,遗传进化分析结果显示病毒的HA基因来自于欧亚类禽型H1N1(EA H1N1)分支的SIV,NA基因来自于北美三重配型H1N2分支的SIV,6个内部基因(PB2、PB1、PA、NP、M和NS)均来自于2009/H1N1分支的病毒。以10~6EID_(50)的剂量经鼻腔途径感染小鼠后,能够引起小鼠出现明显的体重下降,其中有1只小鼠在感染后第7天体重下降的比率超过25%,判为死亡;感染后第3天在小鼠肺及鼻甲骨中均检测到较高滴度的病毒,含量分别为4.82、4.20 log_(10)EID_(50)·mL^(-1)。结果表明SIV在不断流行的过程中,不同基因型病毒之间发生重组导致出现基因三重配的病毒,病毒对小鼠呈现中等致病力特征,提示应进一步加强对SI的主动监测,从而降低病毒对兽医及公共卫生学风险。

The objective of this study was to investigate the epidemiological situation of swine influenza and viral molecule characteristics in North-eastern China.One H1N2 subtype swine influenza virus,designated as A/swine/Liaoning/FX575/2016(H1N2)(FX575),was isolated from a slaughterhouse in Liaoning province during an active surveillance in 2016.The complete genomic sequence of the strain was sequenced and subjected to phylogenetic analysis,molecular characteristic analysis and genotypic analysis.Then,the viral pathogenesis was carried out by intranasal infecting the six-week-old female BALB/c mice and evaluated by measuring body weight loss of mice and virus replication titer.FX575 was a triple reassortant H1N2 virus,which had the nearest genetic relationship with the H1N2 influenza viruses previously isolated from China.Phylogenetic analysis results demonstrated that HA gene of the isolate belonged to the Eurasian avian-like swine H1N1 lineage,the NA gene was clustered into the North American swine H1N2 lineage,and the six internal genes fell into the pandemic 2009/H1N1 virus lineage,respectively.The virus FX575 could cause significant weight losses of mice within one week after infection,and one mouse with its weight loss exceeding 25 percent was considered dead.The viral replications occurred both in lungs and nasal turbinates,with the titers of 4.82 and 4.20 log 10 EID 50·mL^-1,respectively.The results indicated that continuous reassortments of different genotypes of influenza viruses occurred in the swine population,and the novel reassortant virus showed moderate pathogenicity to mice,which further suggested that the active monitoring of SIV should be strengthened in the future.