广东省10株乙型脑炎病毒的分子特征研究

Molecular Characteristics of 10 Newly Isolated Strains of the Japanese Encephalitis Virus in Guangdong Province,China

了解广东省目前流行的乙型脑炎病毒的基因型别,以及新分离毒株与P3和SA14-14-2疫苗株E蛋白的氨基酸差异,推测疫苗株的可能保护效果。本研究对广东省2017年从蚊虫和蠓虫标本分离的10株乙型脑炎病毒基因组序列测定,利用MEGA软件登录GenBank下载乙型脑炎病毒代表株序列并绘制进化树,同时用ClustalW2软件与疫苗株进行氨基酸同源性比对和E蛋白的序列分析。10株乙型脑炎病毒均属基因I型GI-b组,但分别位于2个不同的、小的进化分枝中。10株新分离病毒与P3和SA14-14-2疫苗株的E蛋白氨基酸同源性分别位于97.40%~97.60%和97.20%~97.40%之间。E基因区段500个氨基酸中,P3株与新分离乙型脑炎病毒株之间共存在17个氨基酸位点的差异(包括12个共同氨基酸的改变),略高于SA14-14-2疫苗株的16个氨基酸位点变异(包括11个共同氨基酸的改变)。其中在DI区的P3和SA14-14-2株分别有1个和3个共同氨基酸变异,DⅡ区各有5个共同氨基酸改变,DⅢ区分别有5个和2个共同氨基酸改变,结构域之外各有1个共同氨基酸的变异。绝大多数变异发生在非关键位点,只在E306和E388处观察到的氨基酸位点变异与疫苗P3株关键位点的改变有关,这两个位点(G306E,E388G)均发生在DⅢ区,而疫苗SA14-14-2未观察到关键位点的改变。总之,广东省流行的乙型脑炎病毒基因型别可能已由Ⅲ型变为I型;疫苗SA14-14-2株及P3株与新分离毒株均具有很高的同源性,绝大多数关键氨基酸位点未发生变异,对新分离病毒均具有良好的免疫保护价值。

We wished to ascertain the genotypes of Japanese encephalitis(JEVs)isolated in Guangdong Province,China.Also we wanted to evaluate the efficiency of the vaccines P3 and SA14-14-2 by comparing the amino acid(aa)differences among vaccine strains and these new isolates.In this study.Ten JEV representative strains from mosquitoes and midges were resuscitated and their genomes sequenced after downloadeding from GenBank.Comparison of the molecular type,evolution and sequence were undertaken by MEGA and ClustalW2.Results showed that all 10 JEV strains belonged to genotype I(GI-b group)and were located in two small clusters.Paired identity values were 97.40%~97.60%and 97.20%~97.40%at the aa level of the E protein among 10 new isolates and two vaccine strains.On the basis of determination of the genotype of these 10 JEV strains,we compared their aa sequences in all three active domains of the E protein with those of the two vaccine strains.Seventeen aa substitutions(including 12 common aa substitutions)were observed among new isolated strains and the P3 strain,and 16 aa substitutions(including 11 common aa substitutions)among newly isolated strains and the SA14-14-2 strain.Of these 1 and 3 common aa mutations were in the DI region,5 and 5 common aa mutations were in the DⅡ region,5 and 2 common aa mutations were in the DⅢregion,and 1 and 1 aa mutations were in the non-active domain,respectively.Most of these substitutions were not located at the key sites of the three active domains of the E protein except for G306 Eand E388 Gsites in the DⅢregion of P3,no key site was found in SA14-14-2.In a conclusion,genotypeⅢ of the prevailing JEV was substituted by genotype I;The high homology value and few aa substitutions in key sites among new isolated strains,suggest that two vaccine strains have good protection against the new isolated strains.