宿主固有免疫分子Mx2抑制乙型肝炎病毒复制的机制研究

Infection by hepatitis B virus (HBV) leads to hepatitis and is closely associated with the development of liver cirrhosis and hepatocellular carcinoma. Currently licensed drugs for the treatment of chronic hepatitis B are limited to nucleos(t)ide analogs and interferons (IFNs). IFNs induce expression of multiple interferon stimulated genes (ISGs). However, IFN-induced effectors that block HBV infection with defined action mechanisms are scarce. Our data showed that type I interferon induced Mx2 expression in two human hepatoma cell lines (HepG2 and Huh-7). Mx2 strongly blocked HBV replication, possibly at the steps of viral RNA transcription and pgRNA encapsidation. Nuclear membrane localization of Mx2 appeared essential for its anti-HBV activities. In this project, multidisciplinary approaches including molecular biology, cell biology and biophysics will be taken to reveal the detailed mechanisms by which Mx2 inhibits HBV replication. Using the in vitro HBV infection models, the proposed studies will establish whether Mx2 is a key IFN-induced effector molecule blocking HBV replication. This project will advance our understanding of how IFNs block HBV replication and help identify new drug targets.

乙肝病毒感染引起肝炎并与肝硬化、肝癌发展密切相关。目前临床上治疗慢性乙型肝炎药物仅限于核苷（酸）类似物和干扰素。干扰素诱导众多干扰素刺激基因表达，但目前作用机理明确的抗乙肝病毒效应基因鲜有报道。本项目前期工作发现I型干扰素诱导肝癌细胞系HepG2和Huh-7表达Mx2基因；Mx2强烈抑制乙肝病毒复制；Mx2可能在HBV RNA转录、pgRNA包装等环节抑制病毒复制；Mx2核膜定位可能与其抑制HBV复制相关。本项目将采用分子生物学、细胞生物学和生物物理学等多学科手段揭示Mx2抗乙肝病毒机制，并采用乙肝病毒感染细胞模型验证Mx2是否干扰素诱导并具有抑制乙肝病毒复制活性的重要效应蛋白。本项目将有助于了解干扰素抗病毒机制并发现新的靶点以利于抗病毒药物设计。

在本项目的资助下，我们通过筛选具有抗病毒活性的宿主蛋白，发现了一个ISG（即MX2）的抑制活性最高。通过多种分子生物学方法我们发现MX2通过抑制病毒松弛环状DNA（relaxed circular DNA）转化成cccDNA和选择性降低病毒RNA转录两种主要途径抑制乙肝病毒感染和复制。通过RNA干扰技术我们发现MX2在干扰素下调乙肝病毒RNA过程中起重要作用。这项工作有助于了解干扰素抑制乙肝病毒复制的机理，也有助于了解乙肝病毒cccDNA形成的复杂生物学过程。相关结果已经发表在肝脏学权威期刊Journal of Hepatology上。