Hepatitis B virus (HBV) is an important human pathogen that can cause severe liver diseases. There are approximately 250 million people in the world that are chronically infected by this virus, resulting in nearly 1 million deaths every year. The current therapies for HBV patients do not generate sustained response in the great majority of HBV patients. Thus, there is an urgent need of better treatments for HBV patients. This, however, will require a better understanding of the life cycle of HBV for the identification of new therapeutic targets. Autophagy is a catabolic process that is important for maintaining cellular homeostasis. Recent studies indicated that HBV could induce autophagy to enhance its replication. By using cell cultures and transgenic mice that carried the entire HBV genome, we previously demonstrated that autophagy was required for HBV DNA replication both in vitro and in vivo. In our preliminary studies, we further discovered the association of DNA replication-competent capsid particles with autophagosomes in hepatoma cells transfected with the HBV genomic DNA. Interestingly, this association was not detected if the HBV core protein, which forms the viral capsid, was expressed by itself. Our further analysis indicated that the HBV capsid particles were also associated with phagophores, the membrane precursor of autophagosomes, regardless of whether the core protein was expressed from the viral genome or by itself. These results, together with the previous reports that genes essential for the formation of phagophores were required for the assembly of HBV capsid particles, indicated an important role of autophagic membranes in HBV capsid particle assembly, maturation and trafficking. During this grant period, we will continue these novel findings to further investigate the role of autophagy in the HBV life cycle. Specifically, we will study the biological significance of the autophagosome-associated HBV nucleocapsids and their possible role in the morphogenesis and egress of HBV particles, the role of phagophores in the assembly of HBV capsid particles, and the mechanism that regulates the association of HBV nucleocapsids with autophagosomes. These studies will provide important information for us to further understand the role of autophagy in the HBV life cycle and facilitate the development of better treatments for HBV patients.
Hepatitis B virus (HBV) is an important human pathogen that can cause severe liver diseases. There are an estimated 250 million HBV carriers in the world, resulting in nearly 1 million deaths every year. The current HBV treatments are less than satisfactory. The goal our proposed research is to understand the life cycle of HBV, which will be important for improving the treatments for HBV patients.