Recombinant DNA techniques in the study of hepatitis B virus infection

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.