The Role of Interleukin-10 During Fatal Alphavirus Encephalomyelitis

描述(申请人提供)：脑炎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。了解严重和致命性脑炎感染的机制对于制定有效的干预措施至关重要。辛德比斯病毒(SV)是典型的甲型病毒，与委内瑞拉、东部和西部的马脑炎病毒有关，这些病毒在美洲引起季节性脑炎暴发。SV在人类中引起轻微疾病，但具有神经元趋向性，并导致小鼠脑脊髓炎。SV的毒力具有年龄依赖性和病毒株依赖性。神经适应性辛德比斯病毒(NSV)是一种能引起所有年龄段小鼠致死性脑脊髓炎的强毒株。病毒清除与瘫痪的发生相关，这表明是免疫反应导致了病理，而不是病毒复制。通过药物治疗或使用免疫缺陷小鼠模型来抑制免疫反应，可以在感染期间产生保护作用，进一步支持免疫病理学的概念。谷氨酸的兴奋毒性也与致命性疾病有关。白介素10(IL-10)是一种抗炎分子，也是免疫反应的先天和获得性手臂的关键调节因子。其经典作用是通过抑制MHC II类分子和共刺激分子的表达来减少T细胞的激活。这会减少促炎细胞因子和趋化因子的产生，从而抑制免疫反应。在谷氨酸兴奋毒性等应激条件下，IL-10还可直接保护神经元免受细胞凋亡的影响。这项拟议的研究旨在确定IL-10在致死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)中参与NSV感染期间死亡的IL-10的关键来源。IL-10报告小鼠将被用来评估中枢神经系统中哪些细胞正在产生IL-10。介导保护所需的IL-10的来源将通过使用缺乏髓系或淋巴系来源的IL-10的小鼠来确定。其次，我们将研究IL-10在调节Th17介导的免疫病理中的作用。IL-10缺陷(IL-10-/-)小鼠将被用来确定在没有IL-10调节的情况下，炎症的程度和神经毒性细胞因子的产生。TH17浸润物及其产物IL-17、IL-23和IL-21的数量将被量化，并将确定在没有IL-10和TH17细胞的情况下的存活率。第三，IL-10作为神经保护剂的作用将通过将NSV作为IL-10载体(dsNSV：IL-10)外源性注射到感染区域，评估其对IL-10-/-和野生型小鼠的发病率和存活的影响，确定其在体外和体内对神经细胞凋亡的影响，并研究其在谷氨酸兴奋毒性中的作用，来确定IL-10作为神经保护剂的作用。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重症和致命性感染的机制的理解，并为治疗的发展提供基础。

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.