New therapeutic strategies in the treatment of hepatitis B virus infection

Principally, because of the association of the chronic carrier state with the development of cirrhotic liver disease and hepatocellular carcinoma, chronic hepatitis B infection is a public health problem of global significance. In the main, therapy for chronic hepatitis B is limited to the use of alpha interferon for a limited number of chronic hepatitis B virus (HBV) carriers who have chronic hepatitis with active viral replication. The development of antiviral nucleoside analogues for the herpes viruses and human immunodeficiency virus (HIV) has resulted in the identification of several compounds which also have activity against HBV. Unfortunately, these agents have not been associated with the clearance of hepatitis B infection, but rather only the suppression of active infection while the patient is receiving medication. In addition, the development of drug-resistance to these agents by the virus will most likely limit their long-term efficacy. Gene therapy has recently been applied to HBV both in vitro and in vivo. This has included the use of antisense oligodeoxynucleotides and RNA, ribozymes, dominant negative mutants and therapeutic HBV vaccines. These newer therapeutic modalities may hold promise as effective treatments for chronic hepatitis B, but to date, have been limited by the problem of delivery to the target cell population or infected organ in vivo. Combination nucleoside analogue therapy may also provide an important treatment modality for chronic hepatitis B, although this will require further investigation.