PD-1/PD-L1通路介导乙型肝炎免疫耐受的分子机制研究

Chronic hepatitis B virus (HBV) infection can induce chronic inflammation, cirrhosis, and eventually hepatocellular carcinoma (HCC). In previous study, we show gradually increased expression of co-inhibitory receptor TIGIT and PD-1 on CD8+ T cells in the liver of HBs-tg mice. Adaptive immune tolerance could be broken by TIGIT blockade，which leads to chronic hepatitis and HCC in HBs-tg mice. We hypothesize the expression of co-inhibitory receptors play an important role in the maintaining of liver tolerance during chronic HBV infection. PD-L1 blockade to HBs-tg mice leads to the breakdown of liver tolerance. HBs-tg mice developed chronic hepatitis after PD-L1 blockade. In this study, we may detect the co-inhibitory receptor expression of chronic HBV patients and HBV transgenic mice. In vivo and in vitro experiments would be used to verify the cellular and molecular mechanism over the PD-1 pathway and liver tolerance. We will detect whether HBsAg-specific CD8+ T cells increase in the liver and whether CD8+ T cells activate dramatically, improve their proliferation and enhance the ability of killing hepatocytes after PD-L1 blockade. We aim to investigate the molecule mechanisms of PD-1 and TIGIT pathways in the maintaining of HBV immune tolerance. This project may provide new theoretical basis on anti-viral checkpoint therapy in the future.

持续性慢性乙肝病毒（HBV）感染可导致肝纤维化，肝硬化和肝癌。前期研究证明HBV转基因（HBs-tg）小鼠高表达抑制性受体PD-1和TIGIT，阻断TIGIT通路后HBs-tg小鼠产生慢性肝炎，继而产生由慢性乙肝感染导致的肝癌。我们推测乙肝感染时抑制性受体的高表达是肝脏免疫耐受维持的重要原因，对HBs-tg小鼠进行PD-L1阻断，肝脏免疫耐受被打破，小鼠产生肝炎。本课题拟从临床乙肝病人和HBs-tg小鼠两方向检测乙肝感染时抑制性受体PD-1的表达；小鼠体内和体外实验PD-L1阻断研究打破耐受的细胞学和分子学机制：PD-L1阻断后肝脏产生HBV特异性CTLs，CD8+ T细胞增殖加快，活化水平提高，对肝细胞杀伤能力增强。本项目旨对乙肝免疫耐受的机制进一步阐述，研究PD-1和TIGIT通路在维持HBV耐受过程中发挥的作用，并深入探究其分子机制，为未来抗病毒的靶点治疗提供更好的理论基础。

该项目旨在研究感染中PD-1的高表达是乙肝和肝癌中免疫耐受的形成和维持的重要原因。主要取得了以下结果：1）肝癌中NKT细胞高表达PD-1，而阻断PD-1通路后，NKT细胞功能增强，活化水平提高，打破耐受，对肝癌细胞的杀伤增强 （OncoImmunology, 2021）。2）新型布尼亚病毒感染中CD8+ T 细胞高表达PD-1，TIGIT。CD8+T 细胞在新型布尼亚病毒感染中主导清除病毒的作用，并且CD14+CD16+单核细胞分泌CXCL10招募CD8+ T细胞发挥抗感染作用（The FASEB Journal, 2023）。除此之外，新型布尼亚病毒感染患者凝血系统被激活，血管内皮损伤（中华检验医学杂志，2022）。以上结果一方面揭示了乙肝病毒感染时PD-1通路介导了NKT细胞的免疫耐受，另一方面，在新型布尼亚病毒感染时CD8+ T细胞表面高表达的PD-1与疾病发展程度也有一定相关性，这些研究结果都对临床疾病的治疗提供潜在的干预手段。