Role of toll-like receptors 2 and 3 in coronavirus-induced encephalitis

描述（由申请方提供）：冠状病毒（CoV）是人类和动物中广泛存在的新兴RNA病毒。小鼠冠状病毒，小鼠肝炎病毒（MHV），是第二组冠状病毒的原型。不同的MHV分离株诱导急性致死性脑炎和脑脊髓炎，并伴有急性和慢性脱髓鞘。在没有明显感染性病毒的情况下，慢性病理变化与疑似或潜在病毒病因的人类CNS疾病相似，如多发性硬化症。在急性感染期间，神经元和神经胶质细胞都被感染。哺乳动物Toll样受体（Toll Like Receptors，TLR）是一类模式识别受体，可检测病原体相关的分子模式。病毒可通过多种TLR触发炎性细胞因子的产生。对病毒感染时CNS中TLR的相互作用和亚细胞定位以及TLR对病毒的感知如何影响脑炎结果知之甚少。冠状病毒感染是否通过TLR激活炎症反应，如果是这样，TLR主要用于先天性反应仍然未知。在这里，我们将测试的假设，冠状病毒可能会抵消先天免疫反应在中枢神经系统的TLR反应的调制。使用两个MHV菌株，显着不同的神经毒力（MHV-JHM，高度神经毒力株，产生严重的，往往是致命的脑炎;和MHV-A59，轻度神经毒力株，诱导急性脑膜脑炎和慢性脱髓鞘），我们有初步的数据表明他们之间的显着差异，在TLR 2和3的表达的调制，并在功能性后果（NF-？B激活，细胞因子产生）的MHV-感受性。因此，我们的具体目标是：1）用一组定义明确的重组野生型和嵌合病毒定义TLR介导的炎症反应的CoV决定簇; 2）通过在野生型和基因敲除小鼠中进行发病机制研究，并在原代小胶质细胞和星形胶质细胞培养物中离体研究细胞因子和趋化因子的产生，确定TLR 2和TLR 3在体内冠状病毒诱导的脑炎中的作用。这个实验模型将提供一个独特的机会，以确定TLR 2和TLR 3介导的神经炎症反应的作用，并更好地了解TLR 2和TLR 3在病毒性脑炎和慢性脱髓鞘中的功能。 公共卫生相关性：TLR途径在病毒识别与病毒发病机制中的相对作用尚不清楚。这个实验模型将提供一个独特的机会，以确定冠状病毒决定因素的TLR 2和3介导的炎症反应，并更好地了解TLRs在病毒性脑炎和慢性脱髓鞘的作用。

DESCRIPTION (provided by applicant): Coronaviruses (CoVs) are widespread emerging RNA viruses in man and animals. Murine CoV, mouse hepatitis virus (MHV), is the prototype of group II CoV. Different MHV isolates induce acute fatal encephalitis and encephalomyelitis associated with acute and chronic demyelination. The chronic pathological changes in the absence of overt infectious virus are similar to human CNS diseases with suspected or potential viral etiologies, such as multiple sclerosis. During acute infection, both neurons and glial cells become productively infected. Mammalian Toll-Like Receptors (TLRs) constitute a family of pattern recognition receptors which detect conserved pathogen-associated molecular patterns. Viruses may trigger inflammatory cytokine production via multiple TLRs. Little is known about the interplay and subcellular localization of TLRs in the CNS in response to viral infections, and how virus sensing by TLRs may affect encephalitis outcome. Whether CoV infection activates inflammatory responses via TLRs and if so, which TLR is primarily utilized for the innate response remains unknown. Here, we will test the hypothesis that CoVs may counteract the innate immune response in the CNS by modulation of TLR responses. Using two MHV strains that markedly differ in their neurovirulence (MHV-JHM, a highly neurovirulent strain that produces severe and often fatal encephalitis; and MHV-A59, a mildly neurovirulent strain that induces acute meningoencephalitis and chronic demyelination), we have preliminary data demonstrating striking differences between them in the modulation of expression of TLR2 and 3, and in the functional consequences (NF-?B activation, cytokine production) of MHV-sensing by TLR2 and 3. Therefore, our Specific Aims are: 1) to define CoV determinants of TLR-mediated inflammatory response with a well-defined set of recombinant wild-type and chimeric viruses; and 2) to determine the role of TLR2 and TLR3 in coronavirus-induced encephalitis in vivo with pathogenesis studies in wild-type and knockout mice, and ex vivo investigating cytokine and chemokine production in primary microglia and astrocyte cultures. This experimental model will provide a distinctive opportunity to define the role of TLR2- and TLR3- mediated neuroinflammatory response and a better understanding of the function of TLR2 and TLR3 in viral encephalitis and chronic demyelination. PUBLIC HEALTH RELEVANCE: The relative contribution of TLRs pathways in viral recognition versus viral pathogenesis is unclear. This experimental model will provide a distinctive opportunity to define coronavirus determinants of TLR2 and 3- mediated inflammatory response and a better understanding of the role of TLRs in viral encephalitis and chronic demyelination.