The Role of Interleukin-10 During Fatal Alphavirus Encephalomyelitis

描述（由申请人提供）：脑性节肢动物传播的病毒正在成为世界范围内死亡和疾病的主要原因。了解严重和致命脑炎感染的机制对于制定有效的干预措施至关重要。Sindbis病毒（SV）是典型的甲病毒，与委内瑞拉、东部和西部马脑炎病毒有关，后者在美洲引起季节性脑炎暴发。SV在人类中引起轻度疾病，但在小鼠中具有神经元倾向性并引起脑脊髓炎。SV的毒力是年龄依赖性和病毒株依赖性的。神经适应性Sindbis病毒（NSV）是一种致命的SV毒株，可在所有年龄的小鼠中引起致命的脑脊髓炎。病毒清除与麻痹的发生有关，这表明是免疫反应引起了病理，而不是病毒复制。通过药物治疗或使用免疫缺陷小鼠模型抑制免疫反应导致感染期间的保护，进一步支持免疫病理学的概念。谷氨酸兴奋性毒性也与致命疾病有关。白细胞介素-10 （IL-10）是一种抗炎分子，是免疫反应的先天和适应性臂的关键调节剂。它的经典作用是通过抑制MHC II类和共刺激分子的表达来降低T细胞的活化。这通过减少促炎细胞因子和趋化因子的产生来抑制免疫反应。IL-10还可以直接保护谷氨酸兴奋性毒性和其他应激条件下的神经元免于凋亡。提出的研究旨在确定IL-10在致命性病毒性脑炎期间在中枢神经系统中的作用。首先，将确定中枢神经系统（CNS）中介导NSV感染期间死亡的IL-10的关键来源。IL-10报告小鼠将用于评估中枢神经系统中哪些细胞产生IL-10。介导保护所需的IL-10的来源将通过使用骨髓或淋巴源性IL-10缺乏的小鼠来确定。其次，IL-10在调节TH17介导的免疫病理中的作用将被检验。IL-10缺陷（IL-10 -/-）小鼠将被用来确定炎症的程度和产生的神经毒性细胞因子，发生在没有IL-10调节。测定TH17的浸润量及其产物IL-17、IL-23、IL-21的数量，并测定缺乏IL-10和TH17细胞的存活情况。第三，我们将以非NSV为载体，通过外源性给药于感染部位来确定IL-10作为神经保护剂的作用（dsNSV:IL-10），并评估其对IL-10 -/-和野生型小鼠的发病率和存活率的影响，确定其对体外和体内神经元凋亡的影响，并研究其在谷氨酸兴奋毒性中的作用。确定IL-10在介导致死性病毒性脑脊髓炎病理中的作用将增加我们对严重和致死性感染机制的理解，并为治疗开发提供基础。

DESCRIPTION (provided by applicant): Encephalitic arthropod-borne viruses are emerging as a major cause of death and disease worldwide. Understanding the mechanisms involved in severe and fatal encephalitic infections is critical in developing effective interventions. Sindbis virus (SV), the prototypic alphavirus, is related to Venezuelan, eastern, and western equine encephalitis viruses, which cause seasonal outbreaks of encephalitis in the Americas. SV causes mild disease in humans, but has a neuronal tropism and causes encephalomyelitis in mice. The virulence of SV is age-dependent and virus-strain dependent. Neuroadapted Sindbis virus (NSV) is a virulent strain of SV that causes fatal encephalomyelitis in mice of all ages. Viral clearance correlates with the onset of paralysis suggesting that the immune response is causing pathology, not viral replication. Inhibition of the immune response by treating with pharmaceuticals or by using immunodeficient mouse models leads to protection during infection, further supporting the notion of immunopathology. Glutamate excitotoxicity is also implicated in fatal disease. Interleukin-10 (IL-10) is an anti-inflammatory molecule and a key regulator of both the innate and adaptive arms of the immune response. Its classic effects are to reduce T cell activation by inhibiting expression of MHC class II and co-stimulatory molecules. This dampens the immune response by reducing the production of pro-inflammatory cytokines and chemokines. IL-10 can also directly protect neurons from apoptosis in models of glutamate excitotoxicity and other stress conditions. The proposed research is aimed at determining the role IL-10 has in the central nervous system during fatal viral encephalitis. First, the critical source of IL-10 in the central nervous system (CNS) mediating mortality during NSV infection will be determined. IL-10 reporter mice will be used to evaluate which cells are producing IL-10 in the CNS. The source of IL-10 necessary for mediating protection will be determined by using mice that are deficient in either myeloid- or lymphoid-derived IL-10. Second, the role of IL-10 on regulating TH17 mediated immunopathology will be examined. IL-10 deficient (IL-10 -/-) mice will be used to determine the extent of inflammation and production of neurotoxic cytokines that occurs without IL-10 regulation. The amount of TH17 infiltrates and its products, IL-17, IL-23, and IL-21, will be quantified and survival in the absence of IL-10 and TH17 cells will be determined. Third, the role of IL-10 as a neuroprotective agent will be determined by exogenous administration to infected areas using NSV as a vector for IL-10 (dsNSV:IL-10) and evaluating its effects on morbidity and survival in IL-10 -/- and wild-type mice, determining its effects on neuronal apoptosis in vitro and in vivo, and examining its role in glutamate excitotoxicity. Determining the role of IL-10 in mediating fatal viral encephalomyelitis pathology will increase our understanding of the mechanisms responsible for severe and fatal infections and provide a basis for therapeutic development.