四川省流行性乙型脑炎病毒优势基因型的研究

目的了解四川省乙脑主要流行区乙脑病毒的分子生物学特性，为防治提供依据。方法对2007-2010年间分离到的13株乙脑病毒进行PreM和E基因区扩增，采用MEGA5生物学软件完成氨基酸序列和病毒进化树分析。结果基因分型显示13株均属于基因I型。13株病毒之间比较，PreM基因核苷酸和氨基酸同源性为97％-100％和98．7％-100％，E基因核苷酸和氨基酸同源性为97．8％～99．9％和99．6％～100％，其同源性极高。13株病毒与2004年四川分离株比较E基因核苷酸同源性在97．7％～99．6％之间，氨基酸同源性在98．6％-100％之间；PreM基因的核苷酸同源性在96．2％-99．1％之间，氨基酸同源性在97．5％-98．7％之间；与疫苗株P3和SA14—14—2比较E基因核苷酸和氨基酸同源性分别为87．6％～88．3％和97％～97．8％；PreM基因核苷酸和氨基酸同源性分别为84．1％～85．8％和93．7％-96．2％。13株病毒E基因的8个氨基酸毒力位点均没有发生改变。结论四川省乙脑病毒已呈现基因I型为优势型别的态势，其PreM和E区核苷酸和氨基酸高度保守，关键的氨基酸毒力位点没有变化，提示目前使用的疫苗对流行株的感染具有保护作用。

Japanese encephalitis virus with genotype I is predominant in Sichuan Province

Objective To understand molecular characteristics of Japanese encephalitis virus （JEV） isolated from the major Japanese encephalitis epidemic areas in Sichuan Province, and to provide the foundation for JEV prevention. Methods 13 JEV strains were isolated from mosquitoes in Sichuan during 2007-2010, E genes and preM genes were sequenced and phylogenetic analyses were performed using MEGA5 molecular software. Results Phylogenetic analysis indicated that all 13 JEV strains from Sichuan belonged to genotype I, homologies at nucleotide level and deduced amino acid level in PreM gene were 97% -100% and 98.7% -100% , and 97.8% -99.9% and 99. 6% -100% in E gene, respectively. Homologies at nucleotide level and deduced amino acid level in PreM gene between 13 JEV strains and JEV isolated in 2004 in Sichuan were 96.2%-99. 1% and 97.5%-98.7%, and were 97.7%-99. 6% and 98.6% -100% in E gene, respectively. By comparison with vaaeine strains P3 and SA14-14-2, homologies at nueleotide level and deduced amino acid level were 84. 1%-85.8% and 93.7%-96.2% in PreM gene, and were 87.6%-88.3% and 97%-97.8% in E gene, respectively. The neurovirulence-related 8 amino acid sites encode by E gene remained unchanged in 13 JEV strains. Conclusion JEV with genotype I predominated in Sichuan, nucleotide sequences and deduced amino acid sequences in PreM gene and E gene were highly conserved, key neurovirulence-rerlated sites remained unchanged. It suggested currently used vaccine is still capable of preventing JEV infection.