Recombinant DNA techniques have recently contributed a great deal of informations on hepatitis B virus (HBV)
infection. Serum HBV-
DNA appeared as the most sensitive marker of viral replication activity both in
hepatitis B e antigen (
HBeAg)-positive and in anti-HBe-positive patients. In the latter group, a significant correlation between serum
viral DNA positivity and
liver disease activity was present. In our experience, more than 50% of anti-HBe-positive cases with chronic
liver disease showed circulating HBV-
DNA, while none of healthy
HBsAg chronic carriers was found positive for serum HBV-
DNA. In type B acute
hepatitis, viral
nucleic acid sequences were detectable only in a small number of uncomplicated cases, but were observed in all the patients who progressed to
chronic hepatitis. HBV-
DNA represents therefore an early and useful prognostic parameter in acute
infection. Several epidemiological studies have established a striking correlation between HBV
infection and development of
hepatoma. Using molecular hybridization techniques,
viral DNA has been identified in
liver cancer cells. Finally, HBV-
DNA has also been identified in the pancreas, kidney, skin, bile ducts and in cells of the vascular system. In addition, the presence of viral genome has been recently identified in circulating lymphocytes of patients with acute or chronic
HBsAg-positive
hepatitis. These findings add further informations to the understanding of viral biology and of virus-host interactions in the natural history of the
infection and associated
liver disease.