朱海珍 荀圳 邓日林 田仁云 郭萌萌 陈生稳 刘倩 郭艳霞

摘   要：为了研究乙型肝炎病毒（Hepatitis B virus，HBV）能否借助肿瘤细胞的抗免疫机制来逃逸机体免疫，利用HBV感染去肝细胞，研究受感染后的肝细胞对宿主免疫应答的变化. 通过实时荧光定量PCR的方法分析HBV感染后的肝细胞内Axin和PD-L1的转录水平，发现HBV不影响Axin和PD-L1的转录水平，采用蛋白免疫印迹技术发现HBV能下调肝细胞内Axin蛋白水平，同时上调PD-L1蛋白水平. 进一步在细胞内转染表达HBV的组成蛋白的质粒，通过蛋白免疫印迹技术发现HBV的组成蛋白HBx能下調细胞内Axin蛋白的表达. 通过数据相关性分析以及泛素化实验发现，Axin能通过增加PD-L1的E3泛素连接酶SPOP的表达，促进PD-L1泛素蛋白酶体降解. 进一步对PD-L1的泛素化方式进行探讨，发现Axin促进PD-L1的K48依赖的泛素化降解作用. 结果表明，HBV可能通过HBx下调Axin和SPOP蛋白水平，抑制PD-L1泛素化降解，进而逃逸宿主免疫应答. 本研究揭示了HBV免疫逃逸新机制，为治疗HBV奠定了新的基础，在一定程度上推动了抗HBV药物开发.

关键词：酶;PD-L1;乙型肝炎病毒;Axin;免疫逃逸;泛素化;HLCZ01细胞

中图分类号：Q71                               文献标志码：A

Mechanism of Induction of PD-L1

by Hepatitis B Virus in Human Hepatocytes

ZHU Haizhen1，2，3†，XUN Zhen1，2，3，DENG Rilin1，2，3，TIAN Renyun1，2，3，

GUO Mengmeng1，2，3，CHEN Shengwen1，2，3，LIU Qian1，2，3，GUO Yanxia1，2，3

（1. College of Biology，Hunan University，Changsha  410082，China;

2. Institute of Pathogen Biology and Immunology，Hunan University，Changsha  410082，China;

3. State Key Laboratory of Chemo/Biosensing and Chemometrics，Hunan University，Changsha 410082，China）

Abstract：In order to explore whether Hepatitis B virus （HBV） can escape the body’s immunity by means of the anti-immune mechanism of tumor cells， this study used HBV to infect hepatocytes， and then explored the changes of the immune response of infected hepatocytes to the host. The transcriptional levels of Axin and PD-L1 in hepatocytes after HBV infection were analyzed by real-time fluorescence quantitative PCR， and it was found that HBV did not affect the transcriptional levels of Axin and PD-L1. Then， western blot was used to find that HBV could down-regulate Axin protein levels in hepatocytes and up-regulate PD-L1 protein levels. Further transfection of plasmid expressing HBV component protein in cells showed that HBx could down-regulate Axin protein expression in cells by western blot. Data correlation analysis and ubiquitin assay showed that Axin promoted pD-L1 ubiquitin proteasome degradation by increasing the expression of E3 ubiquitin ligase SPOP of PD-L1. Further studies on the ubiquitination of PD-L1 showed that Axin promoted the K48-dependent ubiquitination of PD-L1. Based on the above results， we believe that HBV may down-regulate Axin and SPOP protein levels through HBx， inhibit PD-L1 ubiquitination and degradation， and then escape the host immune response. This study reveals a new mechanism of HBV immune escape， lays a new foundation for the treatment of HBV， and promotes the development of anti-HBV drugs to a certain extent.

Key words：enzymes;PD-L1;Hepatitis B virus（HBV）;Axin;immune evasion;ubiquitin;HLCZ01 cell line

乙型肝炎病毒（Hepatitis B virus，HBV）是一种小的嗜肝DNA病毒，是导致慢性肝病的主要原因，可导致病毒性肝炎、肝硬化和肝细胞癌（Hepatic cell carcinoma，HCC）. 据统计，全世界约有2.5亿人长期感染HBV，并有发展为肝硬化甚至肝癌的风险[1]. 病毒和宿主因素都对慢性HBV感染的結果有影响，与其他病原体一样，HBV形成了逃避宿主的免疫防御策略，例如高比率的基因突变率和免疫调节蛋白的……