Immunopathogenesis of hepatitis B virus and hepatitis C virus infection

病毒特异性CD8+T细胞反应在乙型肝炎病毒(乙肝病毒)和丙型肝炎病毒(丙型肝炎病毒)感染的转归和发病机制中起重要作用。通过使用For提供的免疫细胞培养模型，我们小组对这些病毒特异性CD8+T细胞反应在控制感染方面的成功和失败提出了几个新的见解。在第二个资助期内，我们将处理两个主要方面。第一个是关于乙肝病毒特异性效应分子功能对抗病毒疗效的相对贡献。细胞溶解效应机制与非细胞溶解效应机制在乙肝病毒控制中的相对作用尚不清楚。事实上，在乙肝转基因小鼠中的研究表明，非细胞溶解效应分子起主导作用，而在黑猩猩身上的研究也表明了细胞溶解效应分子的重要作用。在这个子项目中，我们将使用一种新的人类免疫学乙肝病毒细胞培养模型来分析急性和慢性乙肝患者的乙肝病毒特异性CD8+T细胞的体外效应功能。这一新建立的模型是基于一种产生乙肝病毒的、表达人类白细胞抗原A2的人肝癌细胞系(HepG2.117)，该细胞株内源性处理乙肝病毒抗原。在我们自己的初步工作中，我们可以证明CD8+T细胞介导的抗病毒效果主要是通过穿孔素依赖的细胞溶解效应功能来介导的。在这个模型中，我们还将分析恢复乙肝病毒特异性CD8+T细胞功能的不同方法，例如通过添加细胞因子和阻断抑制性受体。除了我们已建立的细胞培养系统外，我们还将使用原代人类肝细胞来进一步确定免疫细胞和乙肝病毒感染的肝细胞之间的重要相互作用及其对病毒控制的影响。第二个子项目涉及恢复丙型肝炎病毒特异性CD8+T细胞功能障碍。通过使用HLAA2复制子细胞，我们可以证明丙型肝炎病毒特异性CD8+T细胞通过非细胞溶解(干扰素γ介导)和细胞溶解效应功能来抑制复制，并且从慢性丙型肝炎患者中获得的丙型肝炎病毒特异性CD8+T细胞显示出不能通过细胞因子恢复的抗病毒效果。通过感染细胞培养模型，我们现在将分析丙型肝炎病毒感染是否影响丙型肝炎病毒特异性CD8+T细胞功能和抗病毒效果，以及先天免疫反应(如干扰素α)对CD8+T细胞功能的影响程度，例如通过减少T细胞识别水平以外的抗原负荷。由于尚不清楚丙型肝炎病毒特异性CD8+T细胞的功能障碍是否与正在进行的病毒复制直接相关，以及抑制病毒复制是否会因此导致丙型肝炎病毒特异性T细胞功能的恢复，我们将在接受无干扰素抗病毒治疗的慢性丙型肝炎患者队列中解决这一重要问题。总体而言，这些全面的分析应该会为乙肝和丙型肝炎免疫生物学提供重要的新见解。

Virus-specific CD8+ T cell responses play a major role in outcome and pathogenesis of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection. By using immunological cell culture models provided by the FOR, our group has yielded several novel insights into success and failure of these virus-specific CD8+ T cell responses in controlling infection. During the second funding period we will address two main aspects. The first one deals with the relative contribution of HBV specific effector functions to antiviral efficacy. The relative contribution of cytolytic versus non-cytolytic effector mechanisms in HBV control is poorly defined. Indeed, studies in HBV-transgenic mice have indicated a dominant role of non-cytolytic effector functions while studies in chimpanzees have also shown an important function of cytolytic effector molecules. In this subproject, we will analyze the ex vivo effector function of HBV-specific CD8+ T cells from patients with acute and chronic HBV infection by using a novel human immunological HBV cell culture model. This newly established model is based on an HBV producing, HLA-A2 expressing human hepatoma cell line (HepG2.117) that endogenously processes HBV antigen. In own preliminary work, we could show that CD8+ T cell-mediated antiviral efficacy is primarily mediated by perforin-depending cytolytic effector functions. With this model, we will also analyze different approaches to restore HBV-specific CD8+ T cell function, e.g. by addition of cytokines and blockade of inhibitory receptors. In addition to our established cell culture system, we will also use primary human hepatocytes to further define the important interactions between immune cells and HBV-infected hepatocytes and their impact on viral control. The second subproject deals with the restoration of HCV-specific CD8+ T cell dysfunction. By using HLA-A2 replicon cells, we could show that HCV-specific CD8+ T cells inhibit replication by non-cytolytic (IFNγ-mediated) and cytolytic effector functions and that HCV specific CD8+ T cells obtained from chronically HCV-infected patients show an impaired antiviral efficacy that can not be restored by cytokines. By using the infectious cell culture model, we will now analyze whether HCV infection influences HCV-specific CD8+ T cell function and antiviral efficacy and to what degree innate immune responses (e.g. IFNα) impact on CD8+ T cell function, e.g. by reducing antigen load beyond the level of T cell recognition. Since it is also not known whether the dysfunction of HCVspecific CD8+ T cells is directly linked to ongoing viral replication and whether inhibition of viral replication would thus lead to restoration of HCV-specific T cell functions, we will address this important question in a well defined patient cohort of chronically HCV infected patients undergoing antiviral IFN-free therapy. Overall, these comprehensive analyses should provide important new insights into HBV and HCV immunobiology.