E-cadherin/KLRG1在HBV特异性CD8+T细胞耗竭中的作用

Virus specific T cell exhaustion is one of the main causes for Hepatitis B virus persistent infection, and the mechanism has not been fully elucidated yet. Killer cell lectin-like receptor G1 (KLRG1) is an inhibitory receptor molecule, which is mainly expressed in NK and T cell and produces inhibitory signals to negatively regulate the function of immune cells. E-cadherin is a well known intercellular adhesion molecule, but its role in immunomodulation is less known. Recently, E-cadherin wss found to be the ligand of KLRG1 and take part in T cell exhaustion. Our early work discovered that Hepatitis B virus (HBV) increased the expression of E-cadherin accompanied with down-regulation of ZEB2. In addition, sE-cadherin increased in sera of patients with HBV infection. Therefore, we proposed a hypothesis: HBV enhances E-cadherin expression by down-regulation of ZEB2, and the enhanced E-cadherin stimulates KLRG1 pathway and induces virus specific CD8+ T cell exhaustion, which in turn promotes persist infection. This project aims to elaborate the mechanism that HBV increase the expression of E-cadherin via down-regulation of ZEB2 and the clinical significance in CD8+ T cell exhaustion through stimulating KLRG1. This research may enrich our knowledge about interaction between virus and host and provide an explanation for HBV chronic infection. Furthermore, it may help to explore new therapy targets.

病毒特异性T细胞耗竭是HBV持续存在的重要原因，但具体机制未明。KLRG1是NK细胞和T细胞的一种抑制性受体，其活化可抑制NK细胞和T细胞功能。近年发现E-cadherin是KLRG1的配体，可活化KLRG1信号。我们在前期工作中，发现细胞中HBV可以下调ZEB2的水平并促进E-cadherin的表达，HBV感染者血液中sE-cadherin水平明显增高。据此，本项目提出假说：HBV下调ZEB2的水平，从而促进E-cadherin的表达，通过激活KLRG1通路引起病毒特异性CD8+ T细胞耗竭，导致HBV持续感染。为此，本项目拟综合利用细胞实验、动物实验和临床标本，探讨HBV上调E-cadherin的机制及临床意义，重点解析E-cadherin/LKRG1通路在HBV特异性CD8+细胞耗竭中的作用机制。本项目的实施，将有助于深入理解病毒与宿主的相互关系，并为研发新的治疗靶点提供思路。

乙型肝炎病毒（Hepatitis B virus, HBV）感染是影响我国人民健康的重要公共卫生问题，机体的免疫应答是决定HBV感染发展和转归的重要因素，深入了解HBV感染与宿主免疫系统的相互作用具有重要意义。在慢性HBV感染过程中, 病毒特异性CD8+ T淋巴细胞耗竭是病毒持续存在的重要原因，阻断 CD8+ T细胞耗竭并恢复其功能可能提供新的抗病毒治疗策略。杀伤细胞凝集素样受体KLRG1（killer cell lectin-like receptor subfamily G member 1, KLRG1）是T淋巴细胞表达的抑制性受体分子之一，其在T细胞耗竭中的作用逐渐受到关注。E-cadherin可作为 KLRG1 的配体，通过结合KLRG1 而激活该通路，从而抑制NK细胞的免疫活性。本项目旨在研究HBV感染患者中，KLRG1的表达变化，以及E-cadherin/KLRG1通路对病毒特异性CD8+ T细胞的调控作用。按照课题设计方案，本项目完成了以下研究内容：（1）HBV感染对E-Cadherin表达的影响。实验结果发现，在HepG2细胞中，HBV感染可以下调ZEB2分子的表达，从而促进E-cadherin的上调；在患者血清中，也发现可溶性E-cadherin的显著上调，其水平与肝损伤状况相关；（2）HBV患者CD8+ T细胞KLRG1表达情况与健康对照组有差异；（3）HBV特异性CD8+T细胞KLRG1呈高表达状态，其免疫活化功能受到抑制，表现为CD69、Annexin、IL2、INF-α、TNF-γ等分子较健康对照组有明显变化；（4）细胞实验中，纯化的sE-cadherin可以对抗HBV特异性T细胞对HBV的抑制作用；（5）sE-cadherin可影响HBV特异性CD8+ T细胞的AKT磷酸化水平；（6）HBV转基因小鼠CD8+ T细胞KLRG1表达高于对照组小鼠。