Abstract

The use of L(–)SddC [β-l-2′,3′-dideoxy-3′-thiacytidine (lamivudine, 3TC)] for the treatment of Herpes B virus (HBV) infection is hindered by the emergence of drug-resistance associated with the L526M, L550V, and L526M/M550V mutations of the viral DNA polymerase (DP). The interactions of the anti-HBV compounds 2′,3′-dideoxy-2′,3′-didehydro-β-l(–)-5-fluorode-oxycytidine and 2′-fluoro-5-methyl-β-l-arabinofuranosyluracil triphosphate with HBV DP and its L(–)SddC-associated mutants have not been studied. The e antigen-negative variant of HBV associated with the G1896A mutation in the precore region has a high prevalence. Its effect on HBV DP is unclear. Because HBV DNA synthesis occurs in the nucleocapsid, we examined the kinetics of the reverse transcriptase activity from wild-type (wt) and mutated DPs with the wt or G1896A-mutated RNA template in the nucleocapsid. The effects of this template mutation on the activities of these l-nucleoside triphosphates were also examined. Results indicated that these DP mutations increased the K_m values of deoxy-NTPs and decreased the efficiencies (V_max/K_m) of DPs. The additional L526M mutation increased the efficiency of the M550V-mutated DP but no more than that of the L526M-mutated DP. The G1896A mutation had impacts on the interactions between different DPs and deoxy-NTPs, except dCTP. It also had different impacts on the actions of the l-nucleoside triphosphates toward DPs. The L526M and M550V mutations caused a greater decrease in the V_max using the wt RNA template compared with the G1896A-mutated template. The L526M, M550V, and L526M/M550V mutations caused varying degrees of resistance to the different l-nucleoside triphosphates.