Immune Evasion Mechanisms of Neurovirulent Alphaviruses

描述（由申请人提供）：甲病毒是人类疾病的重要原因，可引起从感染性关节炎到致死性脑炎的疾病。虽然甲病毒感染的分子发病机制已被广泛研究，但对这些病毒如何与宿主免疫反应相互作用并逃避宿主免疫反应知之甚少。在研究辛德毕斯病毒的成年小鼠神经毒力AR 86株时，我们的实验室在病毒非结构蛋白编码区内鉴定了成年小鼠神经毒力的几个决定因素。这些决定簇之一，在nsP 1 538，与宿主I型IFN系统相互作用，因为在该位置具有减毒突变的病毒在体内和体外诱导比野生型病毒显著更多的I型IFN。进一步的分析表明，AR 86非结构蛋白能够通过特异性干扰细胞质RNA传感器RIG-I直接干扰RIG-I介导的I型IFN诱导。RIG-I依赖性IFN诱导途径的特异性拮抗作用的证明代表了甲病毒特异性拮抗I型干扰素系统的第一个证据。因此，提出了以下研究：1）表征病毒非结构蛋白拮抗RIG-I功能的机制，2）确定I型IFN诱导途径中的其它步骤是否也被病毒非结构蛋白靶向，3）确定哪些非结构蛋白或多聚蛋白前体介导RIG-I拮抗作用，和4）确定nsP 1538处的毒力决定子和RIG-1/Mda 5/MAVS干扰素诱导途径之间的相互作用是否有助于通过AR 86调节I型IFN诱导，以及随后对病毒毒力的影响。这项工作有可能通过解剖这些重要的人类病原体与宿主先天免疫系统相互作用的机制，显着推进我们对甲病毒发病机制的理解。甲病毒代表了对人类健康的重大新兴威胁，并且增加对这些病毒如何与宿主先天免疫应答相互作用并破坏宿主先天免疫应答的理解可能有助于开发针对这些病原体的改进的疫苗/治疗剂。此外，由于基于甲病毒的载体正在开发作为疫苗递送平台，因此对这些病毒如何与先天免疫系统相互作用的理解的增加可能导致产生更安全和更具免疫原性的载体。

DESCRIPTION (provided by applicant): Alphaviruses, which can cause diseases ranging from infectious arthritis to lethal encephalitis, are a significant cause of human disease. Though the molecular pathogenesis of alphavirus infections has been extensively studied, relatively little is known about how these viruses interact with and evade the host immune response. In studying the adult mouse neurovirulent AR86 strain of Sindbis virus; our laboratory has identified several determinants of adult mouse neurovirulence within the viral nonstructural protein coding region. One of these determinants, at nsP1 538, interacts with the host type I IFN system, since viruses with an attenuating mutation at this position induce significantly more type I IFN than the wild type virus in vivo and in vitro. Further analysis demonstrated that the AR86 nonstructural proteins are able to directly interfere with RIG-I mediated type I IFN induction by specifically interfering with the cytoplasmic RNA sensor, RIG-I. The demonstration of specific antagonism of the RIG-I dependent IFN induction pathway represents the first evidence for specific antagonism of the type I interferon system by alphaviruses. Therefore, studies are proposed to 1) characterize the mechanism(s) by which the viral nonstructural proteins antagonize RIG- I function, 2) determine whether other steps in the type I IFN induction pathway are also targeted by the viral nonstructural proteins, 3) determine which nonstructural proteins or polyprotein precursors mediate the RIG-I antagonism, and 4) determine whether interactions between the virulence determinant at nsP1 538 and the RIG-I/Mda5/MAVS interferon induction pathway contribute to the regulation of type I IFN induction by AR86, with subsequent effects on viral virulence. This work has the potential to significantly advance our understanding of alphavirus pathogenesis by dissecting the mechanisms by which these important human pathogens interact with the host innate immune system. Alphaviruses represent a significant emerging threat to human health, and an increased understanding of how these viruses interact with and subvert the host innate immune response is likely to assist in the development of improved vaccines/therapeutics against these pathogens. Furthermore, since alphavirus-based vectors are in development as vaccine delivery platforms, the increased understanding of how these viruses interact with the innate immune system is likely to result in the generation of safer and more immunogenic vectors.