Suthar Mehul S, Shabman Reed, Madric Kenya, Lambeth Cassandra, Heise Mark T
Department of Microbiology and Immunology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
J Virol. 2005 Apr;79(7):4219-28. doi: 10.1128/JVI.79.7.4219-4228.2005.
Sindbis virus infection of mice has provided valuable insight into viral and host factors that contribute to virus-induced neurologic disease. In an effort to further define the viral genetic elements that contribute to adult mouse neurovirulence, the neurovirulent Sindbis virus strain AR86 was compared to the closely related (22 single amino acid coding changes and the presence or absence of an 18-amino-acid sequence in nsP3 [positions 386 to 403]) but avirulent Girdwood strain. Initial studies using chimeric viruses demonstrated that genetic elements within the nonstructural and structural coding regions contributed to AR86 neurovirulence. Detailed mapping studies identified three major determinants in the nonstructural region, at nsP1 538 (Ile to Thr; avirulent to virulent), an 18-amino-acid deletion in nsP3 (positions 386 to 403), and nsP3 537 (opal to Cys; avirulent to virulent), as well as a single determinant in the structural genes at E2 243 (Leu to Ser; avirulent to virulent), which were essential for AR86 adult mouse neurovirulence. Replacing these codons in AR86 with those found in Girdwood resulted in the attenuation of AR86, while the four corresponding AR86 changes in the Girdwood genetic background increased virulence to the level of wild-type AR86. The attenuating mutations did not adversely affect viral replication in vitro, and the attenuated viruses established infection in the brain and spinal cord as efficiently as the virulent viruses. However, the virus containing the four virulence determinants grew to higher levels in the spinal cord at late times postinfection, suggesting that the virus containing the four attenuating determinants either failed to spread or was cleared more efficiently than the wild-type virus.
辛德毕斯病毒感染小鼠为研究导致病毒诱导的神经疾病的病毒和宿主因素提供了有价值的见解。为了进一步确定导致成年小鼠神经毒力的病毒遗传元件，将神经毒力的辛德毕斯病毒株AR86与密切相关（22个单氨基酸编码变化以及nsP3中18个氨基酸序列的有无[第386至403位]）但无毒力的格德伍德株进行了比较。使用嵌合病毒的初步研究表明，非结构和结构编码区域内的遗传元件对AR86神经毒力有贡献。详细的图谱研究确定了非结构区域中的三个主要决定因素，分别位于nsP1 538（异亮氨酸变为苏氨酸；无毒力变为有毒力）、nsP3中的18个氨基酸缺失（第386至403位）和nsP3 537（乳白密码子变为半胱氨酸；无毒力变为有毒力），以及结构基因中E2 243处的一个单一决定因素（亮氨酸变为丝氨酸；无毒力变为有毒力），这些对于AR86成年小鼠神经毒力至关重要。用格德伍德株中的密码子替换AR86中的这些密码子会导致AR86减毒，而在格德伍德遗传背景中相应的四个AR86变化则使毒力增加到野生型AR86的水平。减毒突变在体外对病毒复制没有不利影响，减毒病毒在脑和脊髓中建立感染的效率与有毒力病毒相同。然而，含有四个毒力决定因素的病毒在感染后期在脊髓中的水平更高，这表明含有四个减毒决定因素的病毒要么传播失败，要么比野生型病毒更有效地被清除。
