Mechanisms of neuronal injury during virus infection of the CNS

食源性和水源性小核糖核酸病毒（例如肠道病毒 71）是一个全球性健康问题。神经科 与神经毒性非脊髓灰质炎小核糖核酸病毒感染相关的并发症是一种严重的持续健康问题 问题，尤其是儿童。不幸的是，小核糖核酸病毒引起的中枢损伤的机制 神经系统（CNS）尚不清楚。我们认为先天免疫反应是导致 急性感染期间神经元死亡。这与普遍的假设相反，即神经元损失是 仅由病毒介导。虽然我们毫不怀疑某些神经元会因病毒感染而直接死亡， 我们的初步研究结果表明，某些群体，例如海马体中的 CA1 锥体神经元， 被先天免疫反应而不是病毒杀死。我们建立了小鼠模型 使用泰勒氏鼠脑脊髓炎病毒直接测试中枢神经系统小核糖核酸病毒感染的作用 中性粒细胞参与神经细胞凋亡的启动。我们的初步证据表明，在急性期 中枢神经系统小核糖核酸病毒感染后，许多未感染的 CA1 锥体神经元发生凋亡相关死亡 具有氧化损伤、钙蛋白酶活性和半胱天冬酶活性；这种伤害严重降低了认知能力 空间记忆测试。我们进一步观察到中性粒细胞在数小时内浸润海马 感染。中性粒细胞浸润减少具有神经保护作用，而活化的中性粒细胞过继转移至 中性粒细胞反应缺陷的小鼠会诱发海马损伤。最后，用钙蛋白酶抑制剂治疗 保护海马神经元免于死亡并保留认知功能而不限制 介导宿主防御和病毒清除所必需的炎症反应。在这些基础上 观察结果我们假设中性粒细胞通过钙蛋白酶依赖性机制杀死海马神经元 中枢神经系统急性小核糖核酸病毒感染期间。我们打算解决以下实验问题：1） 中性粒细胞是否足以杀死海马神经元？； 2) 钙蛋白酶是关键执行者 中性粒细胞对急性中枢神经系统感染的反应导致海马神经元死亡？我们建议 多项创新，包括使用活体动物成像和中性粒细胞过继转移，以解决 这些问题。我们提议的关键概念是，虽然炎症关键介导宿主防御 病毒感染后，炎症反应可能间接杀死神经元，因此治疗干预 旨在防止神经元死亡而不阻碍病毒炎症控制的目的可能会保留宿主功能。

Foodborne and waterborne picornaviruses such as enterovirus 71 are a global health issue. Neurologic complications associated with neurovirulent non-polio picornavirus infection are a serious ongoing health problem, especially in children. Unfortunately, the mechanisms of picornavirus-induced injury to the central nervous system (CNS) are unclear. We propose that the innate immune response is an important cause of neuron death during acute infection. This is in contrast to the prevailing hypothesis that neuron loss is mediated solely by virus. While we do not doubt that some neurons die directly as the result of viral infection, our preliminary findings suggest that certain populations, such as CA1 pyramidal neurons in the hippocampus, are killed by the innate immune response rather than by the virus. We have established a mouse model of picornavirus infection of the CNS using the Theiler's murine encephalomyelitis virus to directly test the role of neutrophils in the initiation of neuronal apoptosis. Our preliminary evidence indicates that during acute picornaviral infection of the CNS, many uninfected CA1 pyramidal neurons undergo apoptotic death associated with oxidative injury, calpain activity, and caspase activity; this injury severely reduces cognitive performance in a spatial memory test. We have further observed that neutrophils infiltrate the hippocampus within hours of infection. Reduced neutrophil infiltration is neuroprotective, while adoptive transfer of activated neutrophils into mice with a defective neutrophil response induces hippocampal injury. Finally, treatment with calpain inhibitors protects hippocampal neurons from death and preserves cognitive function without constraining the inflammatory response that is necessary to mediating host defense and viral clearance. On the basis of these observations we hypothesize that neutrophils kill hippocampal neurons via a calpain-dependent mechanism during acute picornaviral infections of the CNS. We intend to address the following experimental questions: 1) are neutrophils necessary and sufficient to kill hippocampal neurons?; 2) is calpain the key executioner of hippocampal neurons during death induced by the neutrophil response to acute CNS infection? We propose several innovations, including the use of live animal imaging and adoptive transfer of neutrophils, to address these questions. The key concept of our proposal is that while inflammation critically mediates host defense to virus infection, the inflammatory response may indirectly kill neurons, and therefore therapeutic interventions aimed at preventing neuronal death without thwarting inflammatory control of virus may preserve host function.