Effect of tenofovir disoproxil fumarate on drug-resistant HBV clones

• We compared tenofovir disoproxil fumarate (TDF) susceptibilities between HBV genotype A and C.
• N236T substitution in HBV RT region is significantly associated with TDF susceptibility.
• Genotypic differences in TDF susceptibility were observed between genotypes A and C in vitro and in vivo.

SummaryBackground & aimsTenofovir disoproxil fumarate (TDF) has been approved for chronic hepatitis B treatment, and favorable susceptibility of hepatitis B virus (HBV) has been indicated. However, differences in TDF susceptibility among HBV genotypes and drug-resistant strains are unclear. In this study, TDF susceptibilities between genotypes A and C were evaluated in vitro and in vivo using several drug-resistant HBV clones.MethodsHBV expression plasmids were constructed from sera of HBV carriers, and drug-resistant substitutions were introduced by site-directed mutagenesis. TDF susceptibility was evaluated by changes of core-associated HBV replication intermediates in vitro or by change of serum HBV DNA in human hepatocyte chimeric mice carrying each HBV clone in vivo.ResultsTDF susceptibilities of lamivudine-resistant clones (rtL180M/M204V) and lamivudine plus entecavir-resistant clones (rtL180M/S202G/M204V) were similar to wild type clones in vitro. However, lamivudine plus adefovir-resistant clones (rtA181T/N236T) acquired tolerance to TDF, and the rtN236T mutation was considered to be a causal substitution for TDF resistance. Furthermore, genotypic differences in TDF susceptibility were also observed between genotypes A and C in vitro, and the differences could be confirmed in vivo (p = 0.023).ConclusionsThe present study indicates that TDF susceptibility varies among HBV genotypes and drug-resistant HBV clones.