Neural stem/progenitor cell fate: pathology and protection during CNS infections

描述（由申请人提供）：在美国，许多不同的病毒引起破坏性中枢神经系统（CNS）感染（例如疱疹病毒、HIV、虫媒病毒），导致严重脑炎、长期神经系统后遗症（癫痫发作、认知缺陷、发育障碍等），与死虽然免疫系统对病毒有强烈的反应，但CNS感染与神经元的急性损伤和神经干/祖细胞（NSPCs）的损失有关。免疫反应甚至可能通过对感染附近未感染细胞的旁观者效应而导致神经病理学。例如，NSPCs对许多促炎介质有反应，这些促炎介质破坏NSPCs产生新的神经元并潜在地抑制CNS修复。病毒、免疫应答和NSPCs之间的相互作用尚未得到很好的理解，并且缺乏用于保护NSPCs或调节CNS中的抗病毒免疫的治疗方式。我们最近的特点的干扰素-γ（IFNγ），免疫细胞产生的抗病毒细胞因子，在中枢神经系统感染的作用。我们假设IFNγ驱动NSPCs产生新的胶质细胞而不是新的神经元，这可能对CNS修复产生深远的影响。使用脑中神经元限制性麻疹病毒感染的转基因小鼠模型（CD 46+小鼠），我们发现IFNγ保留了NSPC池，但无法保护感染新生小鼠中的新生神经元。我们还观察到IFNγ处理的NSPCs中星形胶质细胞标志物的表达增加，表明IFNγ驱动NSPCs产生新的神经胶质细胞，而不是新的神经元。重要的是，在CD 46+模型中，病毒仅限于成熟神经元，允许分析NSPCs上的炎症，而没有直接NSPC感染的混杂效应。在目的1中，我们确定了抗病毒反应的关键成分在改变新生和成年小鼠NSPC增殖和分化中的作用。我们将CD 46+小鼠与各种免疫敲除背景杂交，以专门研究IFNγ和产生大多数IFNγ的免疫细胞（T细胞）在NSPC功能障碍中的作用。因此，这些实验明显适合于确定感染期间抗病毒免疫应答对NSPCs的影响。在目标2中，我们定义了促炎信号分子在IFNγ体外治疗和体内感染期间细胞命运决定中的作用。我们已经建立了原代野生型和敲除NSPCs的体外培养条件，我们将使用药理学抑制剂和siRNA敲除来鉴定参与IFNγ信号传导和细胞命运选择的信号传导分子。这些研究是创新的，因为抗病毒免疫应答在NSPC功能障碍中的作用将独立于病毒的直接影响而被定义。此外，这些研究将确定在NSPCs中决定细胞命运选择的促炎信号分子，建立用于定义和改善CNS感染的长期神经功能缺损的模型系统，并提出研究神经炎症对CNS发育和修复的影响的新方法。

DESCRIPTION (provided by applicant): Many diverse viruses cause devastating central nervous system (CNS) infections in the United States (e.g. herpesvirus, HIV, arboviruses), leading to severe encephalitis, long-term neurological sequelae (seizures, cognitive deficits, developmental disorders, etc.), and death. Though the immune system vigorously responds to the virus, CNS infections are associated with acute damage to neurons and loss of neural stem/progenitor cells (NSPCs). The immune response may even contribute to neuropathology through bystander effects on uninfected cells near the infection. For example, NSPCs are responsive to many pro-inflammatory mediators, which disrupt the production of new neurons by the NSPCs and potentially inhibit CNS repair. The interactions between the virus, the immune response, and NSPCs are not well understood, and therapeutic modalities for protecting NSPCs or modulating anti-viral immunity in the CNS are lacking. We have recently characterized the role of interferon-gamma (IFNγ), an anti-viral cytokine produced by immune cells, during CNS infections. We hypothesize that IFNγ drives NSPCs toward production of new glia instead of new neurons, which could have profound effects on CNS repair. Using a transgenic mouse model of neuron-restricted measles virus infection in the brain (CD46+ mice), we have found that IFNγ preserves the NSPC pool but is unable to protect newly-born neurons in infected neonatal mice. We also observed increased expression of astrocytic markers in IFNγ-treated NSPCs, suggesting that IFNγ drives NSPCs toward production of new glia as opposed to new neurons. Importantly, in the CD46+ model, the virus is restricted to mature neurons, allowing for the analysis of inflammation on NSPCs without the confounding effects of direct NSPC infection. In Aim 1, we determine the role of critical components of the anti-viral response in altering NSPC proliferation and differentiation in neonatal and adult mice. We have crossed the CD46+ mice to a variety of immune-knockout backgrounds to study specifically the role of IFNγ and the immune cells that produce the majority of IFNγ (T-cells) in NSPC dysfunction. Thus, these experiments are distinctly suited to determine the effects of the anti-viral immune response on NSPCs during an infection. In Aim 2, we define the role of pro-inflammatory signaling molecules in cell fate decisions during IFNγ treatment in vitro and during an in vivo infection. We have established in vitro culture conditions for primary wildtype and knockout NSPCs, which we will use with pharmacological inhibitors and siRNA knockdown to identify signaling molecules that are involved in IFNγ signaling and cell fate choices. These studies are innovative because the role of the anti-viral immune response in NSPC dysfunction will be defined independently from the direct effects of the virus. Moreover, these studies will identify pro-inflammatory signaling molecules that dictate cell fate choice in NSPCs, establish a model system for defining and ameliorating the long-term neurological deficits from CNS infections, and propose a new approach for studying the effects of neuroinflammation on CNS development and repair.