Control of Alphavirus Replication in the Nervous System

描述（由申请人提供）：Sindbis病毒（SV）是一种感染神经元并引起小鼠急性脑脊髓炎的甲病毒。结果是年龄依赖性的，新生小鼠会患上致命疾病，而断奶小鼠会产生一种特征明确的免疫反应，导致感染后的恢复，并为研究病毒从神经元中清除的机制提供了一个模型系统。患有严重联合免疫缺陷（SCID）的小鼠不会产生sv特异性的体液或细胞免疫反应，也不能清除病毒。我们已经证明感染性病毒可以通过SV E2糖蛋白抗体（Ab）从中枢神经系统（CNS）中清除，并且可以通过干扰素（IFN）从脊髓运动神经元中清除，但不能通过皮质或海马神经元清除。这两种SV清除过程都涉及不损害受感染神经元的机制。抗体介导的细胞内病毒复制控制不依赖于补体和白细胞，需要感染细胞表面的E2糖蛋白交联。SV复制的下调与Na?？依赖性阳离子通量，抑制病毒出芽，恢复宿主蛋白合成和对IFN-的反应。IFN介导的清除与病毒RNA和蛋白质合成的短暂增加（基因组与亚基因组RNA的比例下降）、细胞蛋白质合成的恢复以及病毒蛋白质合成的减少和病毒RNA转录的抑制有关。病毒清除的非细胞溶解机制导致病毒RNA在中枢神经系统中持续存在。在过去的研究中，我们已经证明年龄依赖性易感性和非细胞溶解性清除都可以用体外分化的神经细胞系来模拟。在目前的应用中，我们提出通过以下具体目的来确定年龄依赖性易感性和免疫介导的细胞内病毒复制控制机制：(1)确定为什么成熟神经元比未成熟神经元更能抵抗SV感染；(2)确定与未成熟神经元相比，成熟神经元中病毒复制的哪些步骤受到限制；(3)确定IFN-？清除成熟神经元中的病毒；(4)确定抗e2抗体清除成熟神经元病毒的机制。

DESCRIPTION (provided by applicant): Sindbis virus (SV) is an alphavirus that infects neurons and causes acute encephalomyelitis in mice. Outcome is age-dependent and newborn mice develop fatal disease while weanling mice develop a well-characterized immune response that leads to recovery from infection and provides a model system for studying the mechanisms by which virus is cleared from neurons. Mice with severe combined immunodeficiency (SCID) do not develop an SV-specific humoral or cellular immune response and cannot clear virus. We have shown that infectious virus can be cleared from the central nervous system (CNS) by antibody (Ab) to the SV E2 glycoprotein and can be cleared from spinal cord motor neurons, but not cortical or hippocampal neurons by interferon (IFN)?. Both of these processes of SV clearance involve mechanisms that do not damage infected neurons. Ab-mediated control of intracellular virus replication is independent of complement and leukocytes and requires cross-linking of the E2 glycoprotein on the surface of the infected cell. Down-regulation of SV replication is associated with improved Na???dependent cation flux, inhibition of virus budding, restoration of host protein synthesis and response to IFN-???. IFN- mediated clearance is associated with transient increases in viral RNA and protein synthesis with a decreased ratio of genomic to subgenomic RNA, recovery of cellular protein synthesis followed by reduced viral protein synthesis and inhibition of viral RNA transcription. Noncytolytic mechanisms for virus clearance result in persistence of viral RNA in the CNS. During the past granting period we have shown that both age- dependent susceptibility and noncytolytic clearance can be modeled with neuronal cell lines differentiated in vitro. In the current application we propose to determine the mechanisms of age-dependent susceptibility and of immune-mediated control of intracellular virus replication through the following specific aims: (1)To determine why mature neurons are more resistant to SV infection than immature neurons; (2)To determine what steps of virus replication are restricted in mature neurons compared to immature neurons; (3) To determine the mechanism by which IFN-? clears virus from mature neurons; and (4) To determine the mechanism by which anti-E2 antibody clears virus from mature neurons.