Mechanism of HCV Internalization into Target Cells

描述(由申请人提供)： 据估计，世界上有2%的人口感染丙型肝炎病毒(丙型肝炎病毒)，并面临发展成威胁生命的肝病的风险。丙型肝炎病毒研究的一个主要目标是了解这种病毒如何选择性地攻击肝细胞，也许还有某些淋巴细胞，但由于缺乏适当的实验模型，极大地限制了对病毒趋向性和进入的研究。该领域的一项重大进展是最近发现与丙型肝炎病毒包膜糖蛋白假型的逆转录病毒颗粒真实地复制了病毒生命周期的早期阶段。根据我们最近使用这一新的实验系统进行的研究，我们假设丙型肝炎病毒包膜糖蛋白与一个受体结合，随后与一个辅助受体(CD81)结合，导致病毒颗粒内化和与细胞膜的低pH依赖融合。令人惊讶的是，我们发现丙型肝炎病毒包膜糖蛋白不能诱导受体介导的、低pH依赖的细胞表面融合，这表明细胞内因素对病毒进入的附着后步骤起关键调节作用。我们实验室正在进行的研究旨在阐明调节导致丙型肝炎病毒与靶细胞膜融合的独特而复杂的级联事件的病毒和细胞因素。在这里，我们建议确定丙型肝炎病毒内化和转运到融合能力细胞内的基本机制。从长远来看，我们计划确定允许丙型肝炎病毒进入特定细胞器的细胞内因素。病毒复制的开始阶段是中和抗体和药物的靶标。因此，对导致病毒进入的下游事件的详细了解至关重要，并可能产生预防或治疗干预的额外目标。这些研究将极大地促进我们对丙型肝炎病毒进入肝细胞的机制的理解，并将作为开发针对病毒复制这一关键步骤的特定抑制剂的基础。

DESCRIPTION (provided by applicant): It is estimated that 2% of the world's population is infected with Hepatitis C virus (HCV) and at risk of developing life-threatening liver disease. A major goal of HCV research is to understand how this virus selectively targets hepatocytes and perhaps also certain lymphocytes, but lack of appropriate experimental models has greatly limited studies of viral tropism and entry. A major advance in the field has been the recent discovery that retroviral particles pseudotyped with HCV envelope glycoproteins authentically replicate the early stages of the viral life cycle. Based on our recent studies using this novel experimental system, we postulate that HCV envelope glycoproteins bind to a receptor and subsequently to a co-receptor (CD81), which leads to internalization of viral particles and low pH-dependent fusion with intracellular membranes. Surprisingly, we discovered that HCV envelope glycoproteins cannot induce receptor-mediated, low pH-dependent fusion at the cell surface, indicating that intracellular factors critically modulate post-attachment steps of viral entry. Ongoing studies in our laboratory aim to elucidate the viral and cellular factors that regulate the unique and complex cascade of events resulting in HCV fusion with target cell membranes. Here, we propose to determine the basic mechanism of HCV internalization and trafficking to fusion-competent intracellular compartments. In the long term, we plan to identify the intracellular factors that allow HCV entry to occur in specific organelles. The entry stage of viral replication constitutes a target for neutralizing antibodies as well as pharmacologic agents. A detailed understanding of the downstream events leading to viral entry is therefore critical and may yield additional targets for preventive or therapeutic intervention. These studies will significantly advance our understanding of the mechanism by which HCV enters liver cells and will serve as a foundation for developing specific inhibitors that target this key step of viral replication.