Astrocyte innate immune mechanisms of post-viral cognitive dysfunction

摘要 该建议的重点是星形胶质细胞在分子机制中的关键作用 黄病毒脑炎的潜在神经认知后遗症。西尼罗河病毒是导致 在美国国内获得的虫媒病毒疾病。除了急性 神经侵袭性综合征和持续性运动缺陷，从WN中恢复的患者 神经侵袭性疾病（WNND）经历显著的长期认知后遗症， 包括高比率的记忆损伤和执行功能异常。我们 最近建立了一种新的小鼠颅内感染恢复模型， 突变型WNV（WNV-NS 5-E218 A），导致小胶质细胞持续活化， 突触消除，成年神经发生减少，空间学习缺陷， 病毒清除后持续数月，这些对突触的影响也被观察到， 死于WNND的患者。虽然这些数据提供了一些分子 解释WNV恢复受试者空间学习不良的机制， 海马回路恢复的潜在缺乏尚不清楚。我们最近 证明WNND与T细胞衍生的干扰素（IFN）γ相关， 小胶质细胞源性补体促进海马CA 3区突触前神经元清除 终末，由于白细胞介素（IL）-1β表达的产生而缺乏恢复 活化的星形胶质细胞事实上，WNV恢复动物中IL-1 R1信号的失活 促进成人神经发生，突触修复，并防止空间学习缺陷。 这些反应性星形胶质细胞也表达最近发现的神经毒性标志物 （H2.D1，Gbp 2，psmb 8），表明病毒诱导的认知效应可能是 通过产生具有重定向细胞命运的星形胶质细胞而延续。事实上， 在人皮质中观察到这些基因中的一些（GFAP、Gpb 2、psmb 8）的表达， 用IFNβ处理的星形胶质细胞，也在WNV感染的CNS中高度表达。之前 研究表明，活化的星形胶质细胞具有多种细胞来源， 小胶质细胞是指导星形胶质细胞增生的潜在关键因素18，19。同样，激活 骨髓细胞内炎性小体复合体的数量与IL-1β有关， IL-1靶向多种细胞类型，包括神经前体细胞的生产20，21。我们 假设巨噬细胞来源的IL-1指导神经元前体细胞朝向 病毒性脑炎时星形胶质细胞的命运我们进一步假设， 恢复后，活化的小胶质细胞促进星形胶质细胞向 神经毒性表型抑制海马修复和恢复 先天性免疫细胞因子对神经认知功能的影响 前体细胞（NPC）。 目的1：确定星形胶质细胞源性抗神经源性细胞因子的细胞靶点 在黄病毒脑炎恢复期的神经认知功能障碍。 目的2：确定指导和维持星形胶质细胞增生的先天免疫机制 在西尼罗河病毒感染和恢复期间。 目的3：确定影响神经相关性的星形胶质细胞对IFNβ的特异性反应 从WNND中恢复时的空间记忆

ABSTRACT This proposal is focused on the pivotal role of astrocytes in molecular mechanisms underlying neurocognitive sequelae of flavivirus encephalitis. WNV is the leading cause of domestically acquired arboviral disease in the United States. In addition to the acute neuroinvasive syndromes and persistent motor deficits, patients that recover from WN neuroinvasive disease (WNND) experience significant long-term cognitive sequelae, including high rates of memory impairment and abnormalities in executive function. We recently established a novel murine model of recovery from intracranial infection with a mutant WNV (WNV-NS5-E218A), which leads to ongoing microglia activation with synapse elimination, decreased adult neurogenesis, and spatial learning defects that persist months after viral clearance These effects on synapses were also observed in patients who succumbed to WNND. While these data provide some molecular explanations for poor spatial learning in WNV-recovered subjects, the mechanisms underlying lack of recovery of the hippocampal circuit are unclear. We recently demonstrated that WNND is associated with T cell-derived interferon(IFN)γ, and microglial-derived complement promote elimination of hippocampal CA3 presynaptic terminals, with lack of recovery due to the generation of interleukin(IL)-1β-expressing activated astrocytes. Indeed, inactivation of IL-1R1 signaling in WNV-recovered animals promotes adult neurogenesis, synaptic repair, and prevents defects in spatial learning. These reactive astrocytes also express recently identified markers of neurotoxicity (H2.D1, Gbp2, psmb8), suggesting viral-induced effects on cognition might be perpetuated by the generation of astrocytes with a redirected cell fate. Indeed, increased expression of some of these genes (GFAP, Gpb2, psmb8) is observed in human cortical astrocytes treated with IFNβ, also highly expressed within the WNV-infected CNS. Prior research has suggested multiple cellular origins of reactive astrocytes with activated microglia being a potential key player in directing astrogliosis18,19. Similarly, the activation of the inflammasome complex within myeloid cells has been implicated in IL-1β production with IL-1 targeting multiple cell types including neural precursor cells20,21. We hypothesize that macrophage-derived IL-1 directs neuronal precursor cells toward an astrocyte fate during viral encephalitis. We further hypothesize that during recovery, activated microglia promote the differentiation of astrocytes towards neurotoxic phenotypes that inhibit hippocampal repair and recovery from neurocognitive deficits via effects of innate immune cytokines on neural precursor cells (NPC). Aim 1: Define the cellular targets of astrocyte-derived, anti-neurogenic cytokines in neurocognitive dysfunction during recovery from flavivirus encephalitis. Aim 2: Define innate immune mechanisms that direct and maintain astrogliosis during WNV infection and recovery. Aim 3: Define astrocyte-specific responses to IFNβ that impact neural correlates of spatial memory during recovery from WNND.