Molecular biology of hepadnavirus replication.

Hepatitis B virus was discovered to be the causative agent of hepatitis B (serum hepatitis) almost 25 years ago. However, a detailed understanding of the biology of this clinically important virus has only developed in the last ten years. Among the problems faced by early researchers, were the very limited host range exhibited by HBV and the lack of any tissue culture system in which to propagate the virus. The advent of molecular cloning techniques and the discovery of HBV-like viruses in certain animals, lead to rapid advances in the late 1970s. More recently, several systems have been described for studying hepadnavirus infection and replication in vitro, which promise to yield exciting developments in the near future. In this chapter we will review the molecular biology of HBV replication, and the contributions made by the various animal models and in vitro systems to our present level of understanding.