乙型脑炎病毒减毒株SA14-14-2在乳鼠脑内连续传代后病毒基因的变化

目的研究乙型脑炎病毒(JEV)减毒株SA14-14-2的编码弱毒力基因变化与病毒毒力关系。方法乙型脑炎病毒减毒株SA14-14-2在乳鼠脑内连续传代,检测各代病毒的生物学特性和病毒主要结构蛋白即E蛋白的基因序列,并与基因库中登录的JEV强毒株SA14和弱毒株的相应序列比较。结果JEVSA14-14-2在乳鼠脑内连续传代后,病毒的复制滴度增加,对小鼠的脑内毒力也有所增强,但仍低于其亲代强毒株SA14的水平。JEVSA14-14-2在乳鼠脑内传1代后,病毒E蛋白的基因序列未发生改变;传第2代时,E107位点氨基酸发生了变化;第3代开始,E138位点氨基酸出现了改变。其他个别位点氨基酸也发生变化,但无规律性。乙型脑炎病毒强弱毒株间发生变化的其余7个氨基酸未再发生改变。结论JEVSA14-14-2在乳鼠脑内传代过程中,E蛋白基因E107和E138位氨基酸是决定病毒毒力的关键氨基酸。其他非结构蛋白基因也可能与毒力有关。

Genetic Property of Attenuated Japanese Encephalitis Virus Strain SA14-14-2 after Subculture in Suckling Mouse Brain

Objective To study the relationship between the genetic change and virulence of attenuated Japanese encephalitis virus(JEV)strain SA14-14-2.Methods Subculture strain SA14-14-2 in suckling mouse brain and analyze the biological properties and gene sequence of protein E of the virus of various passages.Compare the gene sequence of protein E with the corresponding sequences of virulent and attenuated JEV strains reported in GeneBank.Results Both the titer and virulence of strain SA14-14-2 after subculture in suckling mouse brain increased significantly.However,the virulence was still lower than that of virulent JEV strain SA14.The gene sequence of protein E of strain SA14-14-2 showed no change after subculture for 1 passage,but showed changes at sites E107 and E138 after subculture for 2 and 3 passages respectively.The changes of amino acids were also observed at other individual sites,which showed no regularity.However,the amino acids at sites E176,E177,E264,E279,E315,E334 and E439 of strain SA14-14-2,which were different from those of its parental virulent strain SA14,showed no further change.Conclusion During subculture of attenuated JEV strain SA14-14-2 in suckling mouse brain,the amino acids at sites E107 and E138 were keys to the virulence.However,other non-structural protein genes might also be related to virulence.