DUCK HEPATITIS-B VIRUS - DNA-POLYMERASE AND REVERSE-TRANSCRIPTASE ACTIVITIES OF REPLICATIVE COMPLEXES ISOLATED FROM LIVER AND THEIR INHIBITION INVITRO

The duck hepatitis B virus (DHBV)-associated activities of reverse transcriptase and DNA polymerase and their inhibition in vitro were studied. Replicative complexes (RCs) were isolated from DHBV-infected liver by gel chromatography followed by sucrose gradient centrifugation. The RCs were detected by dot blot hybridization, using radiolabeled cloned DHBV DNA as a probe, and by the incorporation of 32 -TTP in the presence of dATP, dCTP, dGTP, and Mg 2+ (endogenous DNA polymerase activity). The endogenous DNA polymerase activity associated with RCs was further studied using exogenous templates: reverse transcriptase and DNA polymerase activities were demonstrated using as substrates 32 P-TTP and poly(rA) p(dT) 12 or poly(dA) p(dT) 12–18 , respectively. Both activities were biochemically characterized. Their inhibition by various antiviral agents was studied in vitro : actinomycin D, ara-ATP, aphidicolin, suramin, chloroquin, and phosphonoformate. Among these, suramin, chloroquin, phosphonoformate, and ara-ATP were shown to be potent inhibitors of viral reverse transcriptase and DNA polymerase. Studies are now in progress to establish their antiviral activity in vivo .