Evaluation of Intrahepatic Immune and Virological Mechanisms of Immunopathology in Chronic Hepatitis B Patients using Fine Needle Aspiration Biopsy

使用细针抽吸活检评估慢性乙型肝炎患者的肝内免疫和免疫病理学病毒学机制

• 批准号: 442362849
• 负责人: Dr. Shirin Nkongolo
• 金额: --
• 依托单位: Klinik für Gastroenterologie, Infektionskrankheiten, Vergiftungen
• 依托单位国家: 德国
• 项目类别: Research Fellowships
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/442362849?language=en
• 关键词: Evaluation; Intrahepatic; Immune; Virological; Mechanisms

T cell exhaustion is a defining characteristic of chronic viral infection. There is arguably no other human disease that results in greater antigen-specific T cell exhaustion than chronic Hepatitis B virus (HBV) infection. A majority of patients are infected at birth. HBV is a DNA virus with a low mutation rate compared to other viruses such as hepatitis C virus (HCV) HCV or human immunodeficiency virus (HIV). Coupled with high virus and antigen load, chronic hepatitis B (CHB) patients display profound exhaustion of T cell immunity. The extreme exhaustion is highlighted in CHB patients with liver cancer, where the Gehring lab showed that even tumor antigen specific T cell responses were greater than HBV-specific responses . Mechanisms of T cell exhaustion have been defined in mouse models and translated to checkpoint inhibitor therapy. Anti-PD-1 therapy partially restores HBV-specific T cell immunity in vitro and may improve therapy in CHB patients. However, checkpoint inhibitor therapy elicits only a partial response because inhibitory receptor expression is only one of several factors governing T cell functionality. For CHB, restoration of T cell immunity during chronic infection means 1) overcoming T cell specific defects of exhaustion and 2) breaking the tolerogenic liver environment – obstacles familiar to cancer immunotherapy.Preliminary work in the Gehring lab investigated blood and liver samples from different patient cohorts to define distinct immune profiles during liver inflammation. Using single-cell RNA sequencing of liver biopsies, they identified a population of CD8 T cells with an activated tissue-resident transcriptional phenotype that was unique to patients with liver inflammation. The population expressed high levels of the inhibitory receptors PD-1, Tim-3 and Lag-3. In contrast to the inhibitory phenotype, this CD8 T cell population was the only one where the antiviral cytokine, IFN-γ, and cytotoxic effector, Fas ligand, were detectable. These data suggest that the environment during liver inflammation overrides inhibitory receptor expression, promoting T cell function. Therefore, we hypothesize that immunologic definition of hepatic flares in CHB patients will provide an immune profile capable of breaking liver tolerance. Defining the inflammatory environment has the potential to identify immunotherapeutic targets that could restore T cell function for immunotherapy of chronic viral infections or cancer. The proposed study will i) validate the phenotype of CD8 T cells corresponding to their genetic signature and determine if the CD8 T cell population is HBV-specific; ii) identify the resting population of T cells from which the activated CD8 T cell population arises and iii) define the inflammatory environment that drives the function of this CD8 T cell population. The goal is to target specific CD8 T cells for immunotherapy in the liver and to define an effective antiviral immune response.

T细胞耗竭是慢性病毒感染的定义特征。可以说，没有其他人类疾病比慢性B型肝炎病毒（HBV）感染导致更大的抗原特异性T细胞耗竭。大多数患者在出生时就被感染。HBV是一种DNA病毒，与其他病毒如丙型肝炎病毒（HCV）、HCV或人类免疫缺陷病毒（HIV）相比，其突变率较低。慢性B型肝炎（CH B）患者伴随着高病毒和抗原负荷，表现出T细胞免疫的严重衰竭。在患有肝癌的CHB患者中，这种极度的耗竭突出显示，Gehring实验室表明，即使是肿瘤抗原特异性T细胞反应也大于HBV特异性反应。T细胞耗竭的机制已经在小鼠模型中定义，并转化为检查点抑制剂治疗。抗PD-1治疗在体外部分恢复HBV特异性T细胞免疫，并可能改善CHB患者的治疗。然而，检查点抑制剂治疗仅产生部分应答，因为抑制性受体表达仅是控制T细胞功能的几个因素之一。对于慢性乙型肝炎，在慢性感染期间恢复T细胞免疫意味着1）克服T细胞特异性耗竭缺陷，2）打破致耐受性肝脏环境-癌症免疫治疗常见的障碍。Gehring实验室的初步工作调查了不同患者队列的血液和肝脏样本，以确定肝脏炎症期间不同的免疫特征。使用肝活检的单细胞RNA测序，他们鉴定了一群具有激活的组织驻留转录表型的CD 8 T细胞，这是肝脏炎症患者所独有的。该群体表达高水平的抑制性受体PD-1、Tim-3和Lag-3。与抑制性表型相反，该CD 8 T细胞群是唯一可检测到抗病毒细胞因子IFN-γ和细胞毒性效应子Fas配体的细胞。这些数据表明，肝脏炎症期间的环境覆盖抑制性受体表达，促进T细胞功能。 因此，我们假设免疫学定义的慢性乙型肝炎患者的肝耀斑将提供一个能够打破肝脏耐受的免疫配置文件。定义炎症环境有可能确定免疫靶点，这些靶点可以恢复T细胞功能，用于慢性病毒感染或癌症的免疫治疗。拟议的研究将i）验证与其遗传特征相对应的CD 8 T细胞表型，并确定CD 8 T细胞群是否具有HBV特异性; ii）鉴定活化的CD 8 T细胞群产生的静息T细胞群，iii）确定驱动该CD 8 T细胞群功能的炎症环境。目标是靶向特异性CD 8 T细胞用于肝脏中的免疫治疗，并定义有效的抗病毒免疫应答。