Ethanol suppresses HBV peptide-MHC Class I presentation on hepatocytes

摘要 乙肝病毒感染是导致肝脏失代偿和肝细胞变性的主要原因之一。 全球约有4亿人感染了乙肝病毒。由于艾滋病的高流行率 在普通人群中饮酒，很大一部分慢性乙肝患者也是慢性的 酗酒者。酒精摄入会延长乙肝病毒的持续时间，从而导致慢性肝炎的建立。这个 饮酒患者的乙肝病毒感染快速进展和严重后果的机制不是 安全。病毒不是细胞致病的，有效的清除需要诱导适应性免疫。 主要通过识别病毒多肽的病毒特异性CD8+细胞毒性T淋巴细胞(CTL)进行应答 感染肝细胞表面的组织相容性复合体(MHC)I类。虽然许多研究都集中在 酒精诱导的免疫反应障碍，关于酒精如何掩盖 为逃避CTL的识别，感染肝细胞表面的HBV肽-MHC-I类复合体 失踪。因此，本研究的主要重点是了解乙醇代谢对人体健康的影响。 乙肝病毒多肽-MHC-I类复合体在乙肝病毒感染肝细胞上的表达。这一点的呈现 细胞膜上的复合体需要胞浆中的蛋白酶体对抗原进行处理，负载多肽 进入MHC I类，与抗原呈递转运体(TAP)组装的多肽负载复合体，其 Tapasin在内质网中的稳定作用，并通过反式高尔基体将该复合体运输到 肝细胞表面。几乎所有这些步骤都依赖于干扰素-伽马。最近我们发现， 乙醇代谢产物乙醛(Ach)抑制乙肝病毒核心肽18-27提呈 肝细胞，伴随蛋白酶体功能失调，TAP1/TAPASIN减少 表达和高尔基碎裂，所有这些共同作用，损害乙肝病毒-MHC-I类复合体 感染的肝细胞的表现。基于这些初步数据，我们提出了假设 乙醇代谢减少乙肝病毒多肽-MHC-I类复合体在肝细胞上的表达 蛋白酶体对病毒表面多肽的裂解和对多肽-MHC-I的破坏 贩运到细胞表面。 我们将利用各种最先进的和创新的技术来测试我们的新假设。三位一体 这项研究的具体目的是：1)检测酒精代谢和乙肝病毒对抗原的影响 MHC-I类限制性抗原呈递到肝细胞的多肽处理；2)确定乙醇如何 代谢对表达乙肝病毒多肽-MHC-I类的载肽复合体转运的影响 肝细胞；3)用人双重组嵌合小鼠验证特异性AIMS 1-2的结果 肝细胞和人体免疫系统。拟议研究的完成将有助于发展 预防酒精滥用患者乙肝持续感染的治疗方法。

ABSTRACT Hepatitis B virus (HBV) infection is one of the leading causes of hepatic decompensation and hepatocellular carcinoma worldwide; approximately 400 million people are infected with HBV. Due to the high prevalence of alcohol consumption in the general population, a significant portion of chronic HBV patients are also chronic alcohol abusers. Alcohol intake prolongs HBV persistence leading to establishment of chronic hepatitis. The mechanisms of rapid HBV infection progression and severe outcomes in alcohol-consuming patients are not clear. The virus is not cytopathogenic, and effective clearance requires the induction of an adaptive immune response, mainly via virus-specific CD8+ cytotoxic T lymphocytes (CTLs), which recognize viral peptide-major histocompatibility complex (MHC) class I on infected hepatocytes. While many studies have focused on alcohol-induced impairments of the immune response, information on how alcohol masks the presentation of HBV peptide-MHC class I complex on infected hepatocyte surfaces for escaping recognition by CTLs is missing. Therefore, the main focus of this study is to understand the effects of ethanol metabolism on the expression of the HBV peptide-MHC class I complex on HBV-infected hepatocytes. The presentation of this complex on cell membranes requires antigen processing by proteasomes in the cytosol, loading of peptides into MHC class I, assembly of peptide-loading complex with transporters for antigen presentation (TAP), its stabilization by tapasin in endoplasmic reticulum, and trafficking of this complex via trans-Golgi to the hepatocyte surface. Almost all of these steps are interferon-gamma dependent. Recently, we have found that the ethanol metabolite, acetaldehyde (Ach), suppresses HBV core peptide 18-27 presentation on HBV+ hepatocytes, which is accompanied by dysregulation of proteasome function, reduction in TAP1/tapasin expression and Golgi fragmentation, all of which work in combination to impair HBV-MHC class I complex presentation on infected hepatocytes. Based on these preliminary data, we put forth the hypothesis that ethanol metabolism decreases the display of HBV peptide-MHC class I complex on the hepatocyte surface by impairing viral peptide cleavage by the proteasome and by disrupting peptide-MHC class I trafficking to the cell surface. We will utilize a variety of state-of-the art and innovative techniques to test our novel hypothesis. The three specific aims of the proposed study are to: 1) Examine the effects of ethanol metabolism and HBV on antigenic peptide processing for MHC class I-restricted antigen presentation on hepatocytes; 2) Determine how ethanol metabolism affects the trafficking of peptide loading complex for expressing HBV peptide-MHC class I on hepatocytes; 3) Validate the results of specific aims 1-2 using chimeric mice double-reconstituted with human hepatocytes and a human immune system. Completion of the proposed studies will help in the development of treatment modalities for preventing the persistence of hepatitis B in alcohol abusing patients.