Innate Immune Responses in Hepatitis E Virus Infectionin the Context of Liver Transplantation

戊型肝炎病毒（HEV）是世界范围内急性病毒性肝炎的常见病因。虽然急性戊型肝炎病毒感染通常是自限性的，但也有一些临床相关的例外。怀孕期间感染基因型1可能导致高达30%的死亡率。在免疫抑制患者中，如器官移植受者，感染HEV基因型3可导致慢性肝炎和随后的肝硬化。最近的一项研究报道了20%的肝移植（LTx）受者因肝酶升高和疑似急性排斥而接受肝活检，由于近年来急性HEV感染的频率增加，特别是在免疫功能低下的患者中，如实体器官移植受者，针对HEV的体液免疫和B细胞表位已被广泛研究，导致检测方法高度改进。然而，先天性细胞免疫应答在HEV感染中的作用尚未得到详细研究。我们与里根斯堡大学临床微生物学和卫生学研究所的Jürgen J. Wenzel教授博士密切合作，在我们的实验室建立了一个使用人肝癌细胞系PLC/PRF/5和Huh-7的体外HEV感染系统。这种新的模型具有的主要优点是，野生型病毒用于感染，而不是一个人工质粒构建的亚基因组克隆，如在许多以前的研究中使用的。本研究的主要目的是分析先天免疫细胞的抗病毒免疫和它们在HEV感染中的作用，特别是在肝移植受体。首先，我们将评估先天性NK细胞在HEV复制背景下的效应子功能，并确定促进NK细胞体外细胞毒性的受体配体相互作用。接下来，我们将研究在体外HEV感染的背景下，免疫抑制和抗病毒药物如RBV对NK细胞的影响。然后，我们将确定是否在急性HEV感染患者和LTx接受者的血清和肝活检中检测到先天免疫细胞活化的证据。最后，我们将前瞻性地研究NK细胞在HEV感染过程中和RBV治疗过程中的激活和功能。总之，通过我们的实验计划，我们将能够在体外和体外LTx受体中描述HEV感染背景下的先天性NK细胞反应。这些观察结果可能有助于解释针对HEV的免疫应答的有限持久性，并引导新的方法来指导LTx接受者的HEV治疗。

The hepatitis E virus (HEV) is worldwide a common cause of acute viral hepatitis. Although acute HEV infections are most often self-limiting, there are some clinically relevant exceptions. Infection with genotype 1 during pregnancy may lead to up to 30% mortality. In immunosuppressed patients, such as organ transplant recipients, infection with HEV genotype 3 can cause chronic hepatitis and subsequent liver cirrhosis. A recent study reported a rate of 20% HEV infections in liver transplant (LTx) recipients undergoing liver biopsy for elevated liver enzymes and suspected acute rejection.Due to the recent increase in the frequency of acute HEV infection especially in immunocompromised patients, such as solid organ transplant recipients, humoral immunity and B-cell epitopes against HEV have been extensively studied, leading to highly improved detection assays. However, the role of innate cellular immune responses during HEV infection has not been studied in detail.In close collaboration with Prof. Dr. med. Jürgen J. Wenzel from the Institute of Clinical Microbiology and Hygiene at the University of Regensburg, we established in our laboratory an in vitro HEV infection system using the human hepatoma cell lines PLC/PRF/5 and Huh-7. This new model has the major advantage that a wild-type virus is used for infection, instead of an artificial plasmid construct with a subgenomic clone, as used in many previous studies.The main purpose of this study is to analyze innate immune cells with respect to their anti-viral immunity and their role in HEV infection, especially in liver transplant recipients. First, we will assess the effector functions of innate NK cells in the context of HEV replication and to identify receptor ligand interactions that facilitate NK cell cytotoxicity in vitro. Next, we will examine the effect of immunosuppression and antivirals such as RBV on NK cells in the context of in vitro HEV infection. Then, we will determine if evidence of activation of innate immune cells is detected in serum and liver biopsies of acute HEV-infected patients and LTx recipients. Finally, we will prospectively investigate NK cell activation and function in the course of HEV infection and during RBV therapy.In summary, with our experimental plans, we will be able to characterize innate NK cell responses in the context of a HEV infection in vitro and ex vivo in LTx recipients. These observations might help to explain the limited durability of immune responses against HEV and lead new approaches to guide HEV treatment in LTx recipients.