[Hepatitis B virus: new markers and their immunology]

Hepatitis B virus (HBV) is one of the most important causes of chronic liver disease. HBV is a DNA virus with an external glycoprotein surface and an internal nucleocapsid which contains the viral genome. HBV infection is revealed by the appearance of specific markers. Some of these markers are well known and their presence in serum is important to understand the behaviour of the disease. Among them HBsAg, HBeAg, anti-HBs and anti-HBe are found in serum, so as anti-Core; the HBcAg may be found in hepatic tissue and marks infectivity and virus replication. In the few last years some new antigens and antibodies have been studied and their importance in diagnosis and follow-up of hepatitis has been recognized. HBxAg, Pre-S and DNA-Polymerase (Pol) seem to be specific and early signals of viral replication. More studies showed the trans-activating properties of HBxAg; actually the X protein seems to be involved in replicative cycle of HBV. Many Authors also demonstrated a relationship between the presence of X in serum and/or liver and the progression of disease to cirrhosis and hepatocellular carcinoma. The Pol antigen and its antibody seem to be very common markers of HBV infection in serum of patients with hepatitis. Moreover their presence is the only signal of viral infection in some patients which have no other marker of HBV. More studies are of course needed to exactly establish the significance of these new markers and their importance for diagnosis and prognosis of HBV infection.