Effects of adenine arabinoside on serum and intrahepatic replicative forms of duck hepatitis B virus in chronic infection.

Adenine arabinoside is an antiviral agent which has been used in a number of clinical studies for the treatment of chronic infections with hepatitis B virus. In order to better understand its effects and mode of action, we treated ducks chronically infected with duck hepatitis B virus with a 2-week course and monitored the effects of the drug on viral replication by studying duck hepatitis B virus DNA in liver and serum using molecular biological techniques. We found the drug to be effective in ducks only at much higher doses than those used in humans. At high doses, adenine arabinoside had a dose-related inhibitory effect on viral replication during treatment, but there was a rapid return toward baseline values soon after the cessation of treatment. The supercoiled form of viral DNA was found to be most resistant to adenine arabinoside therapy, and the drug had a disproportionate inhibitory effect on viral plus (noncoding) strand synthesis. We conclude that adenine arabinoside likely exerts its effect in hepadna virus infections predominantly through inhibition of viral DNA polymerase. On the basis of our current study and previous trials in hepatitis B virus-infected patients, we predict that adenine arabinoside will not efficiently eliminate viral replication in chronic hepadna virus infection, when used as the sole therapeutic modality. Adenine arabinoside may have a role to play as an adjunct to immunomodulation or interferon therapy in chronic hepatitis B virus infection in man.