Conclusions

Abstract

Characterization of the molecular components in HBV have provided sensitive techniques for detection of the various viral markers associated with infection and establishment of vaccines which will decrease infection, disease incidence and sequaelae, including possibly primary hepatocellular carcinoma. Such characterization has also had a major impact upon our understanding of the virus life cycle, virus-host interactions and treatment of disease. The role of reverse transcriptase in the replication cycle of HBV and like viruses, for example, suggests that the life cycle of this group of viruses may be a temporally permuted version of the well known retrovirus life cycle (765). In retroviruses, genomic RNA is reverse transcribed into DNA early after infection, which is used to synthesize new genomic RNA later in infection. With HBV, pregenomic RNA is synthesized first, followed by reverse transcription of the minus DNA strand, and finished by partial plus strand synthesis (964). Further, several studies have shown that shortly after infection of susceptible fibroblasts with avian sarcoma virus (ASV), S1 sensitive linear viral DNA species were found in the cytoplasm (686, 760, 767).