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In vitro evaluation of hepatitis B virus polymerase mutations associated with famciclovir resistance
Author(s) -
Xiong Xiaofeng,
Yang Huiling,
Westland Christopher E.,
Zou Ruiming,
Gibbs Craig S.
Publication year - 2000
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1002/hep.510310132
Subject(s) - famciclovir , penciclovir , adefovir , virology , lamivudine , biology , microbiology and biotechnology , hepatitis b virus , polymerase , dna polymerase , virus , enzyme , biochemistry , herpes simplex virus
Several mutations (V521L, P525L, L528M, T532S, and V555I) in the gene for hepatitis B virus (HBV) polymerase have been identified in HBV isolated from patients that displayed break‐through viremia during famciclovir treatment. To determine whether these mutations cause phenotypic resistance to famciclovir, we compared the inhibition constants ( K i ) of penciclovir triphosphate (PCVTP, the active metabolite of famciclovir) for recombinant wild‐type and mutant HBV polymerases containing these mutations. In in vitro enzymatic assays, the V555I mutation displayed the most resistance (with K i increased by 6.2‐fold) to PCVTP. The V521L and L528M mutations showed moderately decreased sensitivity to PCVTP ( K i increased by >3‐fold). We also analyzed the cross‐resistance profiles of these variants for adefovir and lamivudine, two other antiviral agents that also inhibit DNA replication by HBV polymerase. All 5 famciclovir‐associated mutations were sensitive to adefovir diphosphate (ADVDP) in in vitro enzymatic assays (<2.3‐fold decreased sensitivity). The V521L, L528M, and T532S mutations were also sensitive to lamivudine triphosphate (LAMTP); however, the P525L and V555I mutations displayed moderately decreased sensitivity to LAMTP in enzymatic assays (3.6‐fold decreased sensitivity). The lamivudine‐resistant mutations M552I, M552V, and L528M+M552V, which were previously shown to display 8‐ to 25‐fold resistance to LAMTP, were less resistant (≤3.1‐fold) to PCVTP.