Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China; Department of Hepatology, First Hospital of Jilin University, Changchun, Jilin 130021, China.
J Hepatol. 2015 Apr;62(4):771-8. doi: 10.1016/j.jhep.2014.11.007. Epub 2014 Nov 21.
BACKGROUND & AIMS: Hepatitis C virus (HCV) is a human pathogen that can evade host immunity to cause persistent infection, leading to liver cirrhosis and hepatocellular carcinoma. The transfected 3'UTR of HCV genomic RNA can be recognized by host protein RIG-I to activate interferon production in hepatocytes. However, it is difficult to demonstrate the RIG-I mediated sensing of HCV genomic RNA in the context of HCV infection because HCV-encoded NS3-4A protease can inactivate MAVS, a critical adaptor protein in interferon signaling. Our aim was to identify the viral sensor that triggers interferon response in hepatocytes during HCV infection.
We generated a hepatic cell line that stably expressed mutant MAVS resistant to the NS3-4A cleavage. This cell line allowed us to investigate the interferon signaling pathway in the context of HCV infection. By using the knockdown and knockout technology together with biochemical approaches, we were able to identify the actual viral sensor in hepatocytes during HCV infection.
We showed that HCV infection induced robust interferon response in the cells expressing MAVS resistant to the NS3-4A cleavage. Unexpectedly, the interaction between HCV's 3'UTR and RIG-I seemed to play a minor role in this activation, while another helicase MDA5 played a more important role in sensing HCV infection to trigger interferon response.
Our data demonstrate that MDA5 recognizes HCV to initiate host innate immune response during HCV infection. This study provides insight into how host senses HCV to initiate innate immunity during HCV infection.
丙型肝炎病毒（HCV）是一种能够逃避宿主免疫从而导致持续性感染的人类病原体，进而导致肝硬化和肝细胞癌。HCV 基因组 RNA 的转染 3'UTR 可被宿主蛋白 RIG-I 识别，从而激活肝细胞中干扰素的产生。然而，由于 HCV 编码的 NS3-4A 蛋白酶能够使干扰素信号通路中的关键衔接蛋白 MAVS 失活，因此难以证明 HCV 基因组 RNA 在 HCV 感染情况下被 RIG-I 介导识别。我们的目的是鉴定在 HCV 感染过程中触发肝细胞中干扰素反应的病毒传感器。
我们构建了一株稳定表达对 NS3-4A 切割具有抗性的突变型 MAVS 的肝细胞系。该细胞系使我们能够在 HCV 感染的背景下研究干扰素信号通路。通过使用敲低和敲除技术以及生化方法，我们能够鉴定在 HCV 感染过程中肝细胞中的实际病毒传感器。
我们表明，在表达对 NS3-4A 切割具有抗性的 MAVS 的细胞中，HCV 感染诱导了强烈的干扰素反应。出乎意料的是，HCV 的 3'UTR 与 RIG-I 之间的相互作用在这种激活中似乎作用较小，而另一种解旋酶 MDA5 在感知 HCV 感染以触发干扰素反应方面发挥了更重要的作用。
我们的数据表明 MDA5 识别 HCV，从而在 HCV 感染期间启动宿主先天免疫反应。本研究深入了解了宿主如何在 HCV 感染期间感知 HCV 以启动先天免疫。
