The long-range goal of this research is to develop animal models for use in elucidating the mechanism of hepatitis C, as well as in preclinical studies of candidate therapeutics. The transgenic mice that constitutively express hepatitis C virus (HCV) proteins in the liver have been valuable in some studies in the past. However, they have been less useful as a model for hepatitis due to their inherent tolerance to the viral antigens expressed in the liver. We have taken advantage of the cre/IoxP technology, and developed several transgenic mouse lines with inducible expression of the HCV core, E1, and E2 proteins in the liver. In this grant application, we propose studies aimed at establishing a suitable murine hepatitis C model through much improved induction technologies. We will evaluate a novel hydrodynamics-based transfection protocol. The efficiency of HCV gene induction and potential adverse effects will be examined. In addition, a cell-permeable cre fusion protein will be assessed for its function as the catalyst for HCV transgene recombination in the liver. We will then test the hypothesis that transgenic mice conditionally expressing the HCV proteins will mount immune response to the viral antigens and develop hepatitis. In the event that HCV gene expression alone is not sufficient to result in T cell homing and hepatocellular injuries, we will co-transfect the liver with a plasmid DNA encoding the co-stimulatory signal molecule CD80 or CD86 to increase the level of antigen presentation. The antibody and T cell responses against HCV antigens will then be assessed. The results obtained from these proposed studies will be the bases for future NIH RO1 grant applications.