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

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

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。

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.