CTL Effector Mechanisms in Adenoviral Hepatitis

描述（由申请方提供）：本项目的主要目的是阐明杀死病毒感染肝细胞的免疫机制。作为该项目的一部分进行的研究发现，肝细胞对细胞毒性T淋巴细胞（CTL）杀伤的穿孔素和颗粒酶依赖性机制具有抗性，并且病毒感染的肝细胞从肝脏中的清除主要由利用Fas/FasL、TNF/TNFR 1和/或其他死亡受体介导途径的替代CTL效应机制介导。这些结果使我们推测，肝细胞对穿孔素和颗粒酶介导的CTL效应子途径的细胞毒性作用的抗性在限制肝内免疫应答期间的肝损伤程度方面是重要的。为了解决这一假设，并探讨机制，负责在肝脏抗病毒免疫过程中采用的CTL效应机制的独特剧目，我们建议探索机制，负责抵抗病毒感染的肝细胞的颗粒胞吐途径的CTL效应功能。初步研究结果表明，在抗病毒免疫应答过程中产生的细胞因子分别诱导人和小鼠肝细胞中颗粒酶B特异性抑制剂蛋白酶抑制剂9（PI-9）和丝氨酸蛋白酶抑制剂6（SPI-6）的表达。在拟议的研究中，我们将确定在正常和病毒感染的小鼠肝细胞中表达的丝氨酸蛋白酶抑制剂（serpins）的库，并确定细胞因子在体外和体内调节这种serpin表达的作用。然后，我们将探讨丝氨酸蛋白酶抑制剂和/或组织蛋白酶B在介导肝细胞抵抗颗粒酶和穿孔素，分别发挥的作用。最后，我们将确定是否沉默丝氨酸蛋白酶抑制剂和/或组织蛋白酶B基因在体内使病毒感染的肝细胞对穿孔素和颗粒酶依赖的细胞毒性敏感，从而加速病毒感染的肝细胞的免疫清除和加重病毒性肝炎。

DESCRIPTION (provided by applicant): The broad objective of this project is to elucidate the immune mechanisms responsible for killing of virally infected hepatocytes. Studies conducted as part of this project have found that hepatocytes are resistant to perforin and granzyme dependent mechanisms of cytotoxic T lymphocyte (CTL) killing and that clearance of virally infected hepatocytes from the liver is mediated predominately by alternative CTL effector mechanisms that utilize Fas/FasL, TNF/TNFR1 and/or other death receptor mediated pathways. These results lead us to hypothesize that hepatocyte resistance to the cytotoxic effects of the perforin and granzyme mediated CTL effector pathway is important in limiting the degree of liver injury during intrahepatic immune responses. To address this hypothesis and to explore the mechanisms responsible for the unique repertoire of CTL effector mechanisms employed during anti-viral immunity in the liver; we propose to explore mechanisms responsible for resistance of virally infected hepatocytes to the granule exocytosis pathway of CTL effector function. Preliminary findings indicate that cytokines produced during antiviral immune responses induce expression of the granzyme B specific inhibitors proteinase inhibitor 9 (PI-9) and serine proteinase inhibitor 6 (SPI-6) in human and mouse hepatocytes respectively. In proposed studies, we will determine the repertoire of serine proteinase inhibitors (serpins) expressed in normal and virally infected murine hepatocytes and determine the role of cytokines in regulating such serpin expression in vitro and in vivo. We will then explore the role that serpins and/or cathepsin B play in mediating hepatocyte resistance to granzymes and perforin, respectively. Finally, we will determine whether silencing of serpin and/or cathepsin B genes in vivo renders virally infected hepatocytes susceptible to perforin and granzyme dependent cytotoxicity and thereby accelerates immune clearance of virally infected hepatocytes and exacerbates viral hepatitis.