Introduction

Infection with hepatitis B virus (HBV) can cause either an acute or a chronic hepatitis (Nielsen et al., 1971). Chronic infection is a major health problem affecting over 250 million people worldwide (Ganem & Varmus, 1987). Without treatment, chronic infection with HBV progresses to cirrhosis and/ or hepatocellular carcinoma in over 50% of infected patients. It is still not clear why some infected individuals develop a relatively mild, self-limiting hepatitis whilst others suffer from a prolonged, chronic infection. Recent research suggests that interferon-induced expression of MHC antigens on the surface of infected hepatocytes may play a key role in determining the outcome of infection with HBV.

Viral clearance in acute HBV infection

The majority of healthy adults infected with HBV develops a brief hepatitis, which resolves within a few months and is followed by elimination of the virus. A small percentage of infected adults (less than 5%) and the majority of infected neonates and children (greater than 90%) develop a chronic infection. Research in patients and chimpanzees acutely infected with HBV has provided an insight into the mechanisms underlying the normal eradication of HBV and these studies suggest that induction of MHC expression, by type I interferon (i.e. IFN-α/β), is a key factor in virus eradication.

Following infection with HBV, most adults show a marked increase in the serum concentration of circulating IFN (Ikeda, Lever & Thomas, 1986; Kato, Nakagawa & Kobayashi, 1986; Pignatelli et al., 1986).