Chronic viral hepatitis (due to HBV and HCV) is a major cause of liver disease worldwide, and an increasing cause of death in persons living with HIV/AIDS. Our laboratory studies are aimed at better defining the host-pathogen interactions in these infections, with particular focus on humoral and cellular immune responses, viral evasion, inflammation, fibrosis progression, and drug resistance. We are engaged in synthetic biology approaches to rational vaccine development and understanding the limits on the extraordinary genetic variability of HCV.