STUDIES OF THE NATURAL HISTORY OF HEPATITIS C IN LIVER

慢性丙型肝炎病毒感染已成为美国最重要的病毒性肝炎形式。尽管这种疾病通常会持续多年，但大约20%的慢性丙型肝炎患者会在20年内进展为肝硬变。因此，慢性丙型肝炎导致的肝功能衰竭已成为美国和欧洲肝移植的主要适应症。尽管我们对这种疾病的许多方面的了解都取得了显著的进展，但慢性丙型肝炎患者肝细胞损伤的机制尚不清楚。遗憾的是，目前还没有有效的细胞培养系统和动物模型来研究肝病的发病机制。鉴于这些局限性，我们系统地研究了肝移植后复发丙型肝炎患者的肝损伤演变。通过将移植器官的损伤程度与病毒复制的详细分析相关联，我们希望为这些慢性感染患者的肝细胞损伤的发病机制提供见解。这项建议旨在检验一种假设，即丙型肝炎病毒RNA基因组序列的不同突变模式对肝移植后复发的丙型肝炎患者的肝损伤严重程度有深远的影响。我们的特定目的1是前瞻性地确定丙型肝炎复发患者准种进化与肝细胞损伤之间的关系。在特定目标2中，我们计划深入研究准种的克隆进化，并确定这些病毒株的组织来源，包括重型丙型肝炎复发患者和肝移植术后轻度肝细胞损伤患者。我们计划验证准种复制的主要部位对肝细胞损伤的发展至关重要的假设。我们认为，肝移植后非致病性病毒株的出现是丙型肝炎病毒持续肝外复制的结果，而致病性丙型肝炎病毒株起源于病毒的肝内复制。在具体目标3中，我们计划评估丙型肝炎病毒基因型、病毒循环水平和丙型肝炎病毒准种进化对移植肝组织损伤的长期演变的影响。通过仔细地将病毒的演变与肝移植后复发的丙型肝炎患者所经历的肝细胞损伤的程度相关联，我们希望对这一重要肝病的发病机制提供见解。从这些详细的分析中，我们还希望分离出致病病毒株，稍后可以在细胞培养系统中进行测试。

Chronic hepatitis C virus infection has emerged as the most important form of viral hepatitis in the United States. Although the disease often remains indolent for many years, approximately 20 percent of patients with chronic hepatitis C progress to cirrhosis within 20 years. As a consequence, liver failure from chronic hepatitis C has become the leading indication for liver transplantation both in the United States and Europe. Despite remarkable progress in our understanding of many aspects of this disease, the mechanism of hepatocellular injury in patients with chronic hepatitis C is not well understood. Unfortunately, neither efficient cell culture systems nor animal models are available to study the pathogenesis of the liver disease. Given these limitations, we have systematically examined the evolution of liver injury in patients with recurrent hepatitis C after liver transplantation. By correlating the degree of injury to the transplanted organ with detailed analyses of viral replication we hope to provide insights into the pathogenesis of liver cell injury in these chronically infected patients. This proposal is designed to examine the hypothesis that differing patterns of mutation in the genomic sequence of HCV RNA have a profound influence on the severity of liver injury in patients with recurrent hepatitis C after liver transplantation. Our Specific Aim 1 is to prospectively determine the relationship between evolution of HCV quasispecies and hepatocellular injury in patients with recurrent hepatitis C. In Specific Aim 2 we plan to intensively investigate the clonal evolution of quasispecies and to determine the tissue origin of these viral strains both in patients with severe recurrent hepatitis C and in those with mild hepatocellular injury after liver transplantation. We plan to test the hypothesis that the primary site of quasispecies replication is critical to the development of hepatocellular injury. We propose that emergence of nonpathogenic strains of virus after liver transplantation result from continuous extrahepatic replication of HCV, whereas pathogenic strains of HCV originate from intrahepatic replication of the virus. In Specific Aim 3 we plan to assess in impact of HCV genotype, circulating levels of virus, and evolution of HCV quasispecies on the long term evolution of histologic injury in the transplanted liver. By carefully correlating the evolution of the virus with the degree of hepatocellular injury experienced by patients who develop recurrent hepatitis C after liver transplantation, we hope to provide insights into to the pathogenesis of this important liver disease. From these detailed analyses we also hope to isolate pathogenic strains of virus which can later be tested in cell culture systems.