Leparc-Goffart I, Hingley S T, Chua M M, Jiang X, Lavi E, Weiss S R
Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia 19104, USA.
Virology. 1997 Dec 8;239(1):1-10. doi: 10.1006/viro.1997.8877.
C12, an attenuated, fusion delayed, very weakly hepatotropic mutant of mouse hepatitis virus strain A59 (MHV-A59( has been further characterized. We have previously shown that C12 has two amino acid substitutions relative to wild type virus in the spike protein, Q159L (within a region of S1 shown to bind to viral receptor in an in vitro assay) and H716D (in the proteolytic cleavage recognition site). We have sequenced the rest of the 31-kb genome of C-12 and compared it to wild type virus. Only three additional amino acids substitutions were found, all encoded within the replicase gene. Analysis of C12 in vivo in C57Bl/6 mice has shown that despite the fact that this virus replicates in the brain to titers at least as high as wild type and causes acute encephalitis similar to wild-type, this virus causes a minimal level of demyelination and only at very high levels of virus inoculation. Thus acute encephalitis is not sufficient for the induction of demyelination by MHV-A59. Analysis of mutants isolated at earlier times from the same persistently infected glial cell culture as C12, as well as mutants isolated from a second independent culture of persistently infected glial cells, suggests that both the weakly demyelinating and the weakly hepatotropic phenotypes of C12 are associated with the Q159L amino acid substitution.
C12是小鼠肝炎病毒A59株（MHV - A59）的一种减毒、融合延迟且嗜肝性非常弱的突变体，已得到进一步鉴定。我们之前已经表明，与野生型病毒相比，C12在刺突蛋白中有两个氨基酸替换，即Q159L（在体外实验中显示与病毒受体结合的S1区域内）和H716D（在蛋白水解切割识别位点）。我们对C12的31kb基因组的其余部分进行了测序，并将其与野生型病毒进行了比较。仅发现了另外三个氨基酸替换，均由复制酶基因编码。对C57Bl/6小鼠体内的C12进行分析表明，尽管该病毒在脑中的复制滴度至少与野生型一样高，并引起与野生型相似的急性脑炎，但这种病毒仅在非常高的病毒接种水平下才会导致最低程度的脱髓鞘。因此，急性脑炎不足以诱导MHV - A59引起脱髓鞘。对在早期从与C12相同的持续感染神经胶质细胞培养物中分离出的突变体，以及从第二个独立的持续感染神经胶质细胞培养物中分离出的突变体进行分析表明，C12的弱脱髓鞘和弱嗜肝表型均与Q159L氨基酸替换有关。
