Astrocyte innate immune mechanisms of post-viral cognitive dysfunction

摘要 这一建议的重点是星形胶质细胞在分子机制中的关键作用。 黄病毒脑炎潜在的神经认知后遗症。西尼罗河病毒是主要原因 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障碍，WN康复患者 神经侵袭性疾病(WNND)会有严重的长期认知后遗症， 包括高记忆力损害率和执行功能异常。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-NS5-E218A)，它导致持续的小胶质细胞激活 突触消除，成人神经发生减少，以及空间学习缺陷 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 西尼罗河病毒恢复期受试者空间学习不良的解释及其机制 海马区回路缺乏恢复的潜在原因尚不清楚。我们最近 证实WNND与T细胞衍生干扰素γ有关，以及 小胶质细胞衍生补体促进海马CA3区突触前突触消除 终末期，因IL-1β表达的产生而缺乏恢复 激活星形胶质细胞。事实上，在西尼罗河病毒恢复的动物中，IL-1R1信号失活 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，GBP2，psmb8)，提示病毒对认知的影响可能是 通过星形胶质细胞的生成和细胞命运的重定向而永久存在。事实上，增加了 其中一些基因(gfap、gpb2、psmb8)在人的大脑皮质中表达。 用干扰素β处理的星形胶质细胞在西尼罗河病毒感染的中枢神经系统中也有高表达。之前 研究表明反应性星形胶质细胞具有多个细胞来源 小胶质细胞是引导星形胶质细胞的潜在关键分子。同样，激活 髓系细胞内炎性小体复合体的表达与IL-1β有关 IL-1靶向多种细胞类型的生产，包括神经前体细胞20、21。我们 假设巨噬细胞来源的IL-1引导神经前体细胞 病毒性脑炎期间星形胶质细胞的命运。我们进一步假设，在 复苏后，激活的小胶质细胞促进星形胶质细胞分化为 抑制海马区修复和恢复的神经毒性表型 先天免疫细胞因子对神经的影响导致的神经认知障碍 前体细胞(NPC)。 目的1：确定星形胶质细胞来源的抗神经源性细胞因子的细胞靶点 在黄病毒脑炎康复期间的神经认知功能障碍。 目标2：确定引导和维持星形胶质细胞增多症的先天免疫机制 在西尼罗河病毒感染和康复期间。 目标3：确定星形胶质细胞对干扰素β的特异性反应，以影响神经相关 从WNND恢复过程中空间记忆的变化。

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.