The role of NK cells in immunodysregulation by hepatitis C virus

描述（由申请人提供）：丙型肝炎病毒（HCV）在破坏人体免疫以建立慢性感染方面是显着的；这是一个全球性的健康问题，治疗选择有限，也没有可用的疫苗。该病毒克服宿主先天免疫和适应性免疫并在大多数感染肝细胞中持续存在的机制目前尚不清楚，部分原因是我们对hcv -宿主相互作用导致免疫破坏的理解不完全。我们之前已经证明慢性HCV感染通过上调阴性免疫调节剂介导的免疫失调，包括程序性死亡-1 (PD-1)，细胞因子信号传导抑制因子-1 (SOCS-1)，以及最近的T细胞免疫球蛋白和粘蛋白结构域蛋白-3 （Tim-3）。虽然Tim-3已被证明在慢性病毒感染期间的T细胞衰竭中发挥关键作用，但其在HCV持久性和抗病毒反应中的表达和先天免疫细胞的功能尚不清楚。自然杀伤细胞（NK）是宿主抵御病原体入侵的第一道防线。慢性HCV感染者中有NK细胞功能受损的报道，但NK细胞在HCV感染的临床结果和治疗反应中的作用主要集中在传统的NK受体上，如杀伤免疫球蛋白样受体（KIRs）。我们最近发现，从hcv感染个体分离的NK细胞和与hcv感染的肝细胞孵育的NK细胞上，Tim-3的表达上调。阻断Tim-3信号通路可恢复hcv介导的NK细胞抑制和凋亡。基于这些新发现，我们假设HCV诱导的NK细胞上的Tim-3表达在免疫失调中起着关键作用，因此阻断NK细胞上的Tim-3信号将恢复对HCV感染受损的抗病毒免疫反应。为了验证这一假设，我们将进行以下具体目的：1)与自然解决的HCV感染或健康受试者相比，确定接受抗病毒治疗并确定结果的HCV感染患者的NK细胞中Tim-3表达及其功能的作用。2)利用表达HCV的肝细胞模型系统确定Tim-3在NK细胞上上调的机制，重点研究HCV抗原介导的Tim-3转录、翻译、生物合成和降解的特异性调控。3)确定NK细胞中Tim-3信号通路对宿主抗病毒应答的影响，包括树突状细胞（DC） IL-12表达、NK/自然T （NT）和CD4+/CD8+ T淋巴细胞应答，以及肝细胞干扰素（IFN）信号通路和HCV复制。本提案的总体目标是采用翻译方法，统一概述HCV介导的NK细胞Tim-3上调如何改变宿主对HCV感染的先天免疫反应到适应性免疫反应，从而制定有效的策略来对抗这种常见的病毒性疾病。

DESCRIPTION (provided by applicant): Hepatitis C virus (HCV) is remarkable at disrupting human immunity to establish chronic infection; it is a global health problem with limited treatment options and no available vaccine. The mechanisms by which the virus overcomes host innate and adaptive immunity to persist in the majority of infected hepatocytes is currently unclear, in part due to our incomplete understanding of HCV-host interactions leading to immune disruption. We have previously demonstrated that chronic HCV infection leads to immunodysregulation mediated through up-regulation of negative immunomodulators, including programmed death-1 (PD-1), suppressor of cytokine signaling-1 (SOCS-1), and, most recently, T cell immunoglobulin and mucin domain protein-3 (Tim-3). While Tim-3 has been shown to play a critical role in T cell exhaustion during chronic viral infections, its expression and function o innate immune cells in HCV persistence and antiviral responses remain unknown. Natural killer (NK) cells comprise the first line of host defense against invading pathogens. Compromised NK cell functions have been reported in chronic HCV-infected individuals, but efforts to define the role of NK cells in clinical outcomes of HCV infection and treatment responses have focused primarily on traditional NK receptors, such as killer immunoglobulin-like receptors (KIRs). We have recently discovered that Tim-3 expression is up-regulated on NK cells isolated from HCV-infected individuals and on NK cells incubated with HCV-infected hepatocytes. Blockade of Tim-3 signaling restores HCV-mediated NK cell inhibition and apoptosis. Based on these novel findings, we hypothesize that HCV-induced Tim-3 expression on NK cells plays a pivotal role in immunodysregulation, such that blockade of Tim-3 signaling on NK cells will rescue impaired antiviral immune responses to HCV infection. To test this hypothesis, we will carry out the following specific aims: 1) Define the role of Tim-3 expression and its function on NK cells from HCV-infected patients who have received antiviral therapy with defined outcomes, compared with naturally resolved HCV infection or healthy subjects. 2) Determine the mechanisms by which Tim-3 is up-regulated on NK cells using an HCV-expressing hepatocyte model system, focusing on specific HCV antigen-mediated regulation of Tim-3 transcription, translation, biosynthesis and degradation. 3) Determine the effects of Tim-3 signaling in NK cells on host antiviral responses, including dendritic cell (DC) IL-12 expression, NK/natural T (NT) and CD4+/CD8+ T lymphocyte responses, as well as hepatocyte interferon (IFN) signaling and HCV replication. The overall goal of this proposal is to employ a translational approach to obtain a unified overview of how HCV-mediated Tim-3 up-regulation on NK cells alters host innate to adaptive immune responses to HCV infection, so as to develop effective strategies to combat this common viral disease.