Dr. Ella Sklan Department of Clinical Immunology and Microbiology Sackler School of Medicine Tel Aviv University. Date: Mar. 8, 2009 Title: Host factors required for hepatitis C virus replication Abstract: One hundered and seventy million people worldwide are estimated to be infected with hepatitis C virus (HCV), a major cause of liver disease including liver cirrhosis, and hepatocellular carcinoma. There is no vaccine for HCV and the current thearpy has limited efficacy and serious side effects. HCV is an enveloped virus and its nanoparticle sized virion contains a positive, single-stranded RNA genome. This genome encodes a single ~3000 amino acid polyprotein which is processed into structural proteins composing the mature viral particle and non-structural (NS) proteins involved in replicating the viral genome. Host factors participate in most, if not all, steps of positive-strand RNA virus's life cycle. Our goal is to identify these host factors and their role in the viral life cycle, aiming to translate these findings into novel antiviral strategies. We have recently discovered such an interaction between HCV NS protein 5A (NS5A) and TBC1D20 a protein involved in intracellular transport. TBC1D20 depletion impaired HCV replication, with no effect on cell viability. Currently, we are developing high throughput nanoparticle-based FRET assays, such as quantum dots or gold nanoparticles, in order to screen for small molecule inhibitors of this interaction. Viral particles are thought to contain all the essential proteins needed for initiation of replication in the target cell. To further understand the interaction of HCV with its host, we aim to isolate tissue culture grown viral particles using sucrose density gradients and identify host factors that are integral parts of the mature viral particle using a comprehensive proteomic analysis. Identification of the components of these virions has important implications for understanding the HCV biology and can serve as leads for the development of improved antiviral therapies.