Immune Evasion Mechanisms of Neurovirulent Alphaviruses

描述(申请人提供)：甲型病毒可引起从感染性关节炎到致命性脑炎的各种疾病，是人类疾病的重要原因。虽然甲型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和逃避宿主免疫反应的了解相对较少。在研究Sindbis病毒的成年小鼠神经毒力AR86株时，我们的实验室已经在病毒非结构蛋白编码区确定了成年小鼠神经毒力的几个决定因素。其中一个决定因素，位于nsP1 538，与宿主I型干扰素系统相互作用，因为在该位置具有减弱突变的病毒在体内和体外诱导的I型干扰素明显多于野生型病毒。进一步的分析表明，AR86非结构蛋白能够通过特异性干扰细胞质RNA传感器RIG-I而直接干扰RIG-I介导的I型干扰素的诱导。依赖RIG-I的干扰素诱导通路的特异性拮抗的证明是甲型病毒对I型干扰素系统的特异性拮抗的第一个证据。因此，有必要进行以下研究：1)确定病毒非结构蛋白拮抗RIG-I功能的机制(S)，2)确定I型干扰素诱导途径中的其他步骤是否也是病毒非结构蛋白的靶标，3)确定哪些非结构蛋白或多蛋白前体介导了RIG-I拮抗作用，4)确定NSDP538上的毒力决定簇与RIG-I/MDA5/MAVS干扰素诱导途径之间的相互作用是否有助于AR86诱导I型干扰素，从而对病毒毒力产生影响。这项工作有可能通过剖析这些重要的人类病原体与宿主天然免疫系统相互作用的机制来显著推进我们对甲型病毒发病机制的理解。甲型病毒是对人类健康的一种新的重大威胁，对这些病毒如何与宿主天然免疫反应相互作用和破坏的了解的加深，可能有助于开发针对这些病原体的改进疫苗/疗法。此外，由于基于甲型病毒的载体正在开发中，作为疫苗递送平台，对这些病毒如何与先天免疫系统相互作用的了解的增加可能会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.