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）在破坏人体免疫力以建立慢性感染方面表现突出;它是一个全球性健康问题，治疗选择有限，并且没有可用的疫苗。病毒克服宿主先天性和适应性免疫以在大多数感染的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。我们以前已经证明，慢性HCV感染导致免疫失调介导的负性免疫调节剂，包括程序性死亡-1（PD-1），细胞因子信号转导抑制因子-1（SOCS-1），以及最近，T细胞免疫球蛋白和粘蛋白结构域蛋白-3（Tim-3）的上调。虽然Tim-3已被证明在慢性病毒感染期间的T细胞耗竭中起关键作用，但其在HCV持久性和抗病毒应答中的先天免疫细胞的表达和功能仍然未知。自然杀伤（NK）细胞构成宿主防御入侵病原体的第一道防线。在慢性HCV感染个体中已经报道了NK细胞功能受损，但是确定NK细胞在HCV感染的临床结果和治疗反应中的作用的努力主要集中在传统的NK受体，例如杀伤免疫球蛋白样受体（KIR）。我们最近发现，Tim-3的表达上调的NK细胞从HCV感染的个人和与HCV感染的肝细胞孵育的NK细胞。Tim-3信号传导的阻断恢复HCV介导的NK细胞抑制和凋亡。基于这些新的发现，我们假设HCV诱导的Tim-3在NK细胞上的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信号传导将挽救针对HCV感染的受损的抗病毒免疫应答。为了验证这一假设，我们将进行以下具体目标：1）与自然消退的HCV感染或健康受试者相比，确定Tim-3表达及其对来自接受了具有确定结果的抗病毒治疗的HCV感染患者的NK细胞的功能的作用。2)使用表达HCV的肝细胞模型系统确定Tim-3在NK细胞上上调的机制，重点关注特异性HCV抗原介导的Tim-3转录、翻译、生物合成和降解的调节。3)确定NK细胞中Tim-3信号传导对宿主抗病毒应答的影响，包括树突状细胞（DC）IL-12表达、NK/天然T（NT）和CD 4 +/CD 8 + T淋巴细胞应答，以及肝细胞干扰素（IFN）信号传导和HCV复制。该提案的总体目标是采用翻译方法来获得HCV介导的Tim-3对NK细胞的上调如何改变宿主对HCV感染的先天性至适应性免疫应答的统一概述，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.