阿地致HBV发生rtN236T变异的特性和分子模型分析

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In Vitro Characterization and Molecular Modeling Analysis of a Novel Adefovir Resistance Mutation, rtN236T, in the HBV Polymerase The rtN236T mutation in the HBV reverse transcriptase (RT) confers in vitro and clinical resistance to adefovir. This mutation emerges in <2% of adefovir dipivoxil (ADV)-treated patients after 2 years of ADV therapy. Researchers evaluated the cross-resistance profile and viral replication fitness of the rtN236T mutant in vitro and proposed a hypothesis for the mechanism of rtN236T induced resistance. In vitro drug susceptibility and viral replication fitness were determined by transient transfection of a patient-derived full-length HBV clone with the rtN236T mutation into HepG2 cells. Intracellular HBV replication signals were determined by Southern blotting. A computer model of HBV RT based on HIV-1 and murine leukemia virus RT structures was used to study the possible role of rtN236T. Results The rtN236T mutant studied showed a 9.6-fold decrease in adefovir susceptibility in vitro. Susceptibilities to acyclic phosphonates tenofovir and MCC-478 were also reduced by 4.2- and 8.6-fold, respectively. The rtN236T mutant remained sensitive to lamivudine, L-dT and entecavir with IC50 changes <2.4-fold. Cross resistance to FTC and L-FMAU is being investigated. The rtN236T mutation resulted in >60% reduction in replication capacity. Modeled HBV RT structure suggests that the side chain of the mutated rtN236T may have a more favorable interaction with the γ-phosphate of dATP compared to adefovir diphosphate thus providing for selectivity against adefovir diphosphate and other acyclic phosphonate analogs versus the natural substrate. Conclusion The in vitro cross-resistance profile of the adefovir resistance mutation rtN236T shows full susceptibility to lamivudine and investigational agents entecavir and L-dT. Gilead Sciences, Inc., Foster City, CA, USA, CABM, Rutgers University, Piscataway, NJ. 04/16/04 Reference H Yang and others. In Vitro Characterization and Molecular Modeling Analysis of A Novel Adefovir Resistance Mutation rtN236T in the HBV Polymerase. Abstract 383 (poster). 39th EASL. April 14-18, 2004. Berlin, Germany.