Mechanisms and impacts of astrocyte inflammasome activation during viral encephalitis

项目总结 中枢神经系统(CNS)的病毒感染对宿主构成了特别困难的挑战 免疫系统。病毒必须从中枢神经系统清除，而不会对免疫系统造成重大损害 神经细胞组织。近年来，人们越来越认识到病毒性脑炎的幸存者， 如西尼罗河病毒神经侵袭性疾病(WNND)，患有长期的神经认知后遗症。过去时 我们实验室的研究已经通过直接接种减毒WEST在小鼠身上模拟了这种现象 尼罗河病毒进入第三脑室。在这个模型中，小鼠从脑炎中恢复，但免疫- 中介损害会导致不良的认知后遗症。炎性星形胶质细胞产生白介素1β 病毒感染和产生干扰素γ的T细胞驱动小胶质细胞激活。这些途径中的每一条都是负面的 影响海马区突触恢复、海马区神经发生和视觉空间学习。 星形胶质细胞在体内不直接感染西尼罗河病毒，但它们仍显示NLRP3 炎性小体激活及下游活性Caspase-1和IL-1β的产生。这些信号表明 病毒感染期间星形胶质细胞中NLRP3炎症体激活的驱动激活完全保持不变 未知。然而，星形胶质细胞表达P2嘌呤能受体P2RX7，它可以介导炎症体 巨噬细胞暴露于高浓度细胞外三磷酸腺苷后的激活。在这里，我建议神经元 病毒性脑炎期间突触的消除释放细胞外ATP的超心理水平，导致 星形胶质细胞炎性小体激活。在目标1中，我将通过创作一部小说来证实这一假设 在星形胶质细胞上特异性和诱导性缺失P2RX7的小鼠品系。此外，我建议加强 细胞外ATP水平通过P2RX7向神经干细胞发出信号，推动其向反应性分化 是星形发生而不是神经发生。我推测，这条途径可能会导致缺乏 我们的WNND模型的海马神经发生。在目标2中，我将通过感染来调查这种可能性 携带西尼罗河病毒P2RX7缺陷神经干细胞的动物和监测 海马神经发生与视觉空间学习能力。这些目的加在一起，将成为小说的特征 嘌呤能受体P2RX7在神经侵袭性病毒感染中的功能，潜在识别靶点 用于降低感染后神经认知后遗症严重程度的药物治疗。

PROJECT SUMMARY Viral infections of the central nervous system (CNS) pose a particularly difficult challenge to the host immune system. Virus must be cleared from the CNS without significant immune-mediated damage to neuronal tissues. In recent years, it has been increasingly recognized that survivors of viral encephalitides, such as West Nile virus neuroinvasive disease (WNND), suffer from longterm neurocognitive sequelae. Past research from our laboratory has modeled this phenomenon in mice by direct inoculation of attenuated West Nile virus into the third ventricle of the brain. In this model, mice recover from encephalitis, but immune- mediated damage causes adverse cognitive sequelae. Inflammatory astrocytes produce interleukin-1β after viral infection and interferon-γ-producing T cells drive microglia activation. Each of these pathways negatively impacts hippocampal synapse recovery, hippocampal neurogenesis, and visuospatial learning. Astrocytes are not directly infected by West Nile virus in vivo, but they nonetheless display NLRP3 inflammasome activation and downstream production of active caspase-1 and interleukin-1β. The signals that drive activation of the NLRP3 inflammasome activation in astrocytes during viral infection remain completely unknown. However, astrocytes express the P2 purinergic receptor P2RX7, which can mediate inflammasome activation in macrophages exposed to high concentrations of extracellular ATP. Here, I propose that neuronal synapse elimination during viral encephalitis releases supraphsyiologic levels of extracellular ATP, leading to astrocyte inflammasome activation. In Aim 1, I will seek to confirm this hypothesis by generating a novel mouse strain that specifically and inducibly lacks P2RX7 on astrocytes. In addition, I propose that heightened extracellular ATP levels signal to neuronal stem cells via P2RX7, driving their differentiation towards reactive astrogenesis rather than neurogenesis. I hypothesize that this pathway may contribute towards the lack of hippocampal neurogenesis in our model of WNND. In Aim 2, I will investigate this possibility by infecting animals with P2RX7-deficient neural stem cells with West Nile virus and monitoring for changes in hippocampal neurogenesis and visuospatial learning ability. Together, these Aims will characterize novel functions of the purinergic receptor P2RX7 during neuroinvasive viral infection, potentially identifying a target for pharmacologic therapies that reduce the severity of post-infectious neurocognitive sequelae.