Innate Regulation and CD4+Th1/17 Immunity in TMEV-Induced Demyelination

描述（由申请方提供）：Theiler小鼠脑脊髓炎病毒（TMEV）诱导的脱髓鞘疾病（TMEV-IDD）被广泛认为是病毒诱导的自身免疫介导的脱髓鞘疾病的最相关动物模型。MS被认为涉及自身免疫病理学，但流行病学证据强烈表明病毒触发。TMEV是天然的小鼠病原体，用TMEV的BeAn株脑内接种易感的SJL小鼠导致慢性进行性、炎性免疫介导的脱髓鞘疾病，其与终身持续性CNS病毒感染相关，特征在于痉挛性后肢麻痹。相反，抗性C57 BL/6小鼠产生有效的CTL应答并迅速清除感染。与MS一样，TMEV-IDD的特征在于进行性脱髓鞘，伴随以CD 4 + T细胞和活化的APC（小胶质细胞/巨噬细胞/DC）为主的单核细胞浸润。我们以前的研究表明，脱髓鞘是由病毒特异性CD 4 + T细胞启动的，这些细胞靶向由持续感染的CNS驻留APC呈递的病毒表位。慢性脱髓鞘通过诱导对多种内源性致脑炎髓鞘表位的自身免疫应答介导，所述表位通过表位扩散产生。这项申请建议继续我们的生产性研究，由美国国立卫生研究院PPG资助，在过去的21年。基于广泛的新的初步数据，我们将研究先天免疫调节和先天免疫刺激机制在急性感染的免疫介导的病毒清除水平和慢性脱髓鞘期间自身免疫过程的调节水平上参与调节对TMEV-IDD的易感性/抗性的作用。目的1将采用耗竭、补充和遗传方法检验以下假设：CD 4 + CD 25 + Foxp 3 + T细胞活化通过抑制急性感染期间病毒特异性CD 4、CD 8和抗体应答的发展，在调节对TMEV-IDD的易感性方面发挥主要作用，从而建立CNS病毒持续存在，并最终发展为慢性自身免疫。目的2将测试的假设，髓鞘表位特异性自身反应性Th 1（IFN-3）和Th 17（IL-17）细胞的促炎作用是至关重要的介导脱髓鞘免疫病理学在慢性自身免疫阶段的TMEV-IDD。目的3，将检验外周来源的CNS驻留DC在驱动表位扩散至髓磷脂特异性CD 4 + Th 1/17细胞的活化中起关键作用的假设，所述髓磷脂特异性CD 4 + Th 1/17细胞负责慢性TMEV-IDD中的CNS病理。将测定天然免疫应答（细胞因子、趋化因子和抗原呈递分子的表达）;以及来自TMEV感染小鼠的CNS衍生的DC、MU和小胶质细胞激活T细胞增殖和初始CD 4和记忆CD 4+（Th 1、Th 2和Th 17）和CD 8 + T细胞分化的功能能力。这些研究将为病毒诱导的脱髓鞘的易感性/耐药性机制提供重要信息，并适用于MS和其他CNS炎性疾病的未来治疗策略设计。 公共卫生相关性：多发性硬化症（MS）是一种自身免疫性麻痹性疾病，由免疫细胞介导的中枢神经系统中产生髓鞘的少突胶质细胞的破坏引起。某些形式的MS被怀疑是遗传易感个体中病毒感染的继发结果。我们将采用Theiler小鼠脑脊髓炎病毒感染诱导的MS小鼠模型，研究调节性T细胞在决定不同品系近交系小鼠对疾病的遗传易感性中的作用，并确定树突状细胞（先天免疫系统的特化抗原呈递细胞）的作用，在疾病的急性期诱导病毒免疫和在疾病的慢性期诱导产生破坏性细胞因子（IFN-3和IL-17）的自身免疫T细胞的发展。

DESCRIPTION (provided by applicant): Theiler's murine encephalomyelitis virus (TMEV)-induced demyelinating disease (TMEV-IDD) is widely considered the most relevant animal model of virus-induced autoimmune-mediated demyelinating disease. MS is believed to involve an autoimmune pathology, but epidemiological evidence strongly suggests a viral trigger. TMEV are natural mouse pathogens and intracerebral inoculation of susceptible SJL mice with the BeAn strain of TMEV results in a chronic-progressive, inflammatory immune-mediated demyelinating disorder which is related to life-long persistent CNS virus infection and characterized by spastic hind limb paralysis. In contrast, resistant C57BL/6 mice make a potent CTL response and rapidly clear the infection. Like MS, TMEV-IDD is characterized by progressive demyelination with accompanying mononuclear cell infiltrates dominated by CD4+ T cells and activated APCs (microglia/macrophages/DCs). Our previous studies have shown that demyelination is initiated by virus-specific CD4+ T cells targeting viral epitopes presented by persistently infected CNS- resident APCs. Chronic demyelination is mediated by induction of autoimmune responses to a variety of endogenous encephalitogenic myelin epitopes which arise via epitope spreading. This application proposes continue our productive studies funded by an NIH PPG for the past 21 years. Based on extensive new preliminary data, we will examine the role of innate immune regulatory and innate immune stimulatory mechanisms involved in regulating susceptibility/resistance to TMEV-IDD at both the level of immune- mediated virus clearance to acute infection and regulation of autoimmune processes during chronic demyelination. Employing depletion, supplementation and genetic approaches, Aim 1 will test the hypothesis that activation of CD4+CD25+Foxp3+ Tregs plays a major role in regulating susceptibility to TMEV-IDD by inhibiting development of virus-specific CD4, CD8, and antibody responses during acute infection leading to establishment of CNS virus persistence and hence eventual development of chronic autoimmunity. Aim 2 will test the hypothesis that the pro-inflammatory effects of both myelin epitope-specific autoreactive Th1 (IFN-3) and Th17 (IL-17) cells are critical for mediating demyelinating immunopathology during the chronic autoimmune phase of TMEV-IDD. Aim 3, will test the hypothesis that peripherally-derived, CNS-resident DCs play a critical role in driving the activation of epitope spreading to myelin-specific CD4+ Th1/17 cells responsible for CNS pathology in chronic TMEV-IDD. Innate immune responses (expression of cytokines; chemokines; and antigen presentation molecules); and functional ability of CNS-derived DCs, MUs and microglia from TMEV-infected mice to activate T cell proliferation and differentiation of naove CD4 and memory CD4+ (Th1, Th2 and Th17) and CD8+ T cells by will be determined. These studies will provide important information on the mechanisms underlying susceptibility/resistance in virus-induced demyelination and are applicable for the future design of treatment strategies for MS and other CNS inflammatory diseases. PUBLIC HEALTH RELEVANCE: Multiple sclerosis (MS) is an autoimmune paralytic disease caused by immune cell-mediated destruction of myelin-producing oligodendrocytes in the central nervous system. Certain forms of MS are suspected to occur as a secondary consequence a virus infection in genetically susceptible individuals. We will employ a mouse model of MS induced by infection with Theiler's murine encephalomyelitis virus to study the role of regulatory T cells in determining genetic susceptibility to disease in different strains of inbred mice, and to determine the role of dendritic cells, specialized antigen presenting cells of the innate immune system, both in inducing virus immunity in the acute stages of the disease and in inducing development of autoimmune T cells making destructive cytokines (IFN-3 and IL-17) in the chronic phase of disease.