Role of TLR3 Signaling in Control of HCV

描述（由申请人提供）：丙型肝炎病毒（HCV）感染全球约1.3亿人，对人类健康构成重大威胁。HCV是一种嗜肝RNA病毒，在约70%的感染个体中引起慢性肝脏炎症，使患者处于肝硬化和肝细胞癌的风险中。HCV感染的清除需要发展强有力和广泛的CD 4和CD 8 T细胞应答。不幸的是，这些反应通常失败，并被中间细胞毒性T细胞反应所取代，不能消除感染，但足以引起肝细胞破坏。对HCV的先天免疫反应提供了对抗病毒的第一道防线，并且对于协调随后的T细胞反应至关重要，但它们如何在肝细胞中运作仍然知之甚少。我们最近的数据表明，人肝细胞含有一个功能性Toll样受体-3（TLR 3）信号通路，该通路感知HCV感染并导致促炎细胞因子和趋化因子的产生，这些细胞因子和趋化因子是将T细胞募集到肝脏的核心。然而，TLR 3感知病毒复制过程中产生的HCV双链（ds）RNA并导致NF-κ B活化和随后诱导促炎介质的机制尚不清楚。我们推测这些分子事件在HCV-肝细胞相互作用是至关重要的宿主对HCV的免疫反应。因此，更好地理解这些分子事件对于推进我们对HCV的宿主免疫应答和肝细胞中TLR 3信号转导机制的认识至关重要，并为开发丙型肝炎的新型免疫疗法奠定基础。拟议的工作涉及两个具体目标。目的1将确定病毒复制过程中产生的HCV dsRNA被内体/溶酶体区室中的TLR 3感知的机制。我们将描述自噬在TLR 3依赖的宿主对HCV感染的反应中的作用，并鉴定和表征在HCV感染期间被招募到内溶酶体以促进TLR 3信号传导的细胞蛋白。目的2将描述TLR 3通路下游的信号转导机制，HCV通过该通路激活NF-κ B并随后诱导促炎细胞因子和趋化因子。我们还将确定来自特定丙型肝炎患者队列的诊断性肝活检标本中选定的先天免疫信号分子和促炎介质的表达，并确定其与肝脏炎症的可能关系。

DESCRIPTION (provided by applicant): Hepatitis C virus (HCV) infects approximately 130 million people worldwide and poses a major threat to human health. HCV is a hepatotropic RNA virus that causes chronic hepatic inflammation in ~70% of infected individuals, putting patients at risk for cirrhosis and hepatocellular carcinoma. Clearance of HCV infection requires the development of vigorous and broad CD4 and CD8 T cell responses. Unfortunately, these responses often fail and are substituted with an intermediate cytotoxic T cell response unable to eliminate the infection but strong enough to cause hepatocyte destruction. The innate immune responses to HCV provide the first line of defense against the virus and are pivotal for orchestrating subsequent T cell responses, but how they operate in hepatocytes remains poorly understood. Our recent data suggest that human hepatocytes contain a functional Toll-like receptor-3 (TLR3) signaling pathway that senses HCV infection and leads to production of proinflammatory cytokines and chemokines which are central to recruiting T cells to the liver. However, the mechanisms by which TLR3 senses HCV double-stranded (ds) RNAs generated during viral replication and results in NF-kB activation and subsequent induction of proinflammatory mediators are unclear. We hypothesize that these molecular events in HCV-hepatocyte interactions are crucial in host immune responses to HCV. Therefore a better understanding of these molecular events is crucial for advancing our knowledge on host immune responses to HCV and the mechanisms of TLR3 signaling in hepatocytes, and lays the foundation for developing novel immunotherapies for hepatitis C. The work proposed involves two specific aims. Aim 1 will determine the mechanism by which HCV dsRNAs generated during viral replication are sensed by TLR3 in endosome/lysosome compartments. We will delineate the role of autophagy in TLR3- dependent host response to HCV infection, and identify and characterize cellular proteins that are recruited to endolysosomes to facilitate TLR3 signaling during HCV infection. Aim 2 will characterize the signaling mechanisms downstream of the TLR3 pathway by which HCV activates NF-kB and subsequent induction of proinflammatory cytokines and chemokines. We will also determine the expression of selected innate immune signaling molecules and proinflammatory mediators in diagnostic liver biopsy specimens from a specific cohort of hepatitis C patients and define their possible relationship to hepatic inflammation.