Valsamakis A, Schneider H, Auwaerter P G, Kaneshima H, Billeter M A, Griffin D E
Molecular Microbiology and Immunology, Johns Hopkins School of Hygiene and Public Health, Baltimore, Maryland, USA.
J Virol. 1998 Oct;72(10):7754-61. doi: 10.1128/JVI.72.10.7754-7761.1998.
An understanding of the determinants of measles virus (MV) virulence has been hampered by the lack of an experimental model of infection. We have previously demonstrated that virulence phenotypes in human infections are faithfully reproduced by infection of human thymus/liver (thy/liv) implants engrafted into SCID mice, where the virus grows primarily in stromal cells but induces thymocyte apoptosis (P. G. Auwaerter et al., J. Virol. 70:3734-3740, 1996). To begin to elucidate the roles of the C protein, V protein, and the 5' untranslated region of the F gene (F 5'UTR) in MV infection in vivo, the replication of strains bearing mutations of these genes was compared to that of the parent sequence-tagged Edmonston strain (EdTag). Growth curves show that mutants fall into two phenotypic classes. One class of mutants demonstrated kinetics of growth similar to that of EdTag, with decreased peak titers. The second class of mutants manifested peak titers similar to that of EdTag but had different replication kinetics. Abrogation of V expression led to delayed and markedly prolonged replication. Additionally, thymocyte survival was prolonged and implant architecture was preserved throughout the course of infection. In contrast, massive bystander thymocyte death occurred after infection with EdTag and all other mutants. A mutant which overexpressed V in Vero cells (V+) had the opposite phenotype of the A mutant not expressing V (V-). V+ grew more rapidly than EdTag with 100-fold-greater levels of virus production 3 days after infection. These results suggest that C, V, and the F 5'UTR are accessory factors required for efficient virus replication in vivo. In addition, thymocyte survival after V- infection suggests this protein may play multiple roles in pathogenesis of MV infection of thymus. Since these recombinant mutant viruses grew identically to the parent virus in Vero cells, the data show that thy/liv implants are an excellent model for investigating the determinants of MV virulence.
由于缺乏感染的实验模型，对麻疹病毒（MV）毒力决定因素的理解受到了阻碍。我们之前已经证明，通过将人胸腺/肝脏（thy/liv）植入物移植到SCID小鼠体内进行感染，可以忠实地再现人类感染中的毒力表型，在这种情况下，病毒主要在基质细胞中生长，但会诱导胸腺细胞凋亡（P.G. Auwaerter等人，《病毒学杂志》70:3734 - 3740，1996）。为了开始阐明C蛋白、V蛋白和F基因的5'非翻译区（F 5'UTR）在体内MV感染中的作用，将携带这些基因突变的毒株的复制与亲本序列标记的埃德蒙斯顿毒株（EdTag）的复制进行了比较。生长曲线表明，突变体分为两个表型类别。一类突变体表现出与EdTag相似的生长动力学，但其峰值滴度降低。第二类突变体表现出与EdTag相似的峰值滴度，但具有不同的复制动力学。V表达的缺失导致复制延迟且明显延长。此外，胸腺细胞存活时间延长，并且在整个感染过程中植入物结构得以保留。相比之下，用EdTag和所有其他突变体感染后发生了大量旁观者胸腺细胞死亡。在Vero细胞中过表达V的突变体（V +）具有不表达V的A突变体（V -）的相反表型。V +比EdTag生长得更快，感染后3天病毒产生水平高100倍。这些结果表明，C、V和F 5'UTR是病毒在体内有效复制所需的辅助因子。此外，V -感染后胸腺细胞存活表明该蛋白可能在MV感染胸腺的发病机制中发挥多种作用。由于这些重组突变病毒在Vero细胞中的生长与亲本病毒相同，数据表明thy/liv植入物是研究MV毒力决定因素的优秀模型。
