[Kinetics of HBV mutants conferring adefovir resistance (rtn236t) and a method to detect them rapidly].
OBJECTIVE
The aim was to build a PCR-RFLP method for detecting rtN236T mutants and to observe their kinetics in chronic hepatitis B (CHB) patients.


METHODS
Seven CHB patients who had suboptimal viral response or viral breakthrough under adefovir mono-therapy were studied. Part of the HBV reverse transcriptional gene from serial sera samples was sequenced with PCR products or cloned HBV DNA; mutations at rt236 were simultaneously analyzed by a PCR-RFLP assay. Genetic diversity of HBV was observed by calculating Hamming distance within domains B, C and D of RT.


RESULTS
Three patients had viral breakthrough and one with suboptimal viral response had adefovir-resistance mutants, one had rtA181V mutation and three had rtN236T mutation. A novel PCR-RFLP assay based on restriction enzyme HpaI or DraI for on the detection of rtN236T mutant was established, which detected 10% minor strains with 100% specificity. Mutants (rtA181V or rtN236T) appeared 0-8 months earlier than the viral breakthrough, then afterwards became the dominant ones. In one patient after stopping the adefovir therapy, 3 months later a wild type virus re-took again the mutant one (rtN236T); in one patient who developed a rt236T mutant after 132 weeks of adefovir treatment, a novel mutant (rtN236V) appeared and then became the dominant one while adefovir treatment continued.


CONCLUSIONS
A rapid and easy method was established to detect rtN236T mutants. Mutants for adefovir-resistance accumulated rapidly then became dominant, but they could be taken over again by a wild type or novel mutant HBV.
Chen
Jin-jun
JJ
Department of Infectious Diseases, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China.
Ma
Shi-wu
SW
Wang
Zhan-hui
ZH
Sun
Jian
J
Hou
Jin-lin
JL
D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000328:Adult; D000998:Antiviral Agents / Q000494:pharmacology*; D004279:DNA, Viral / Q000235:genetics; D024882:Drug Resistance, Viral / Q000187:drug effects* / Q000235:genetics; D006509:Hepatitis B / Q000821:virology*; D006515:Hepatitis B virus / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D063065:Organophosphonates / Q000494:pharmacology*; D016133:Polymerase Chain Reaction / Q000379:methods; D012150:Polymorphism, Restriction Fragment Length
D000998:Antiviral Agents; D004279:DNA, Viral; D063065:Organophosphonates; C053001:adefovir; D000225:Adenine