A novel mutation pattern emerging during lamivudine treatment shows cross-resistance to adefovir dipivoxil treatment.
OBJECTIVE
This study was conducted to clarify the resistance profile of a novel mutation pattern emerging during lamivudine (3TC) therapy and showing cross-resistance to adefovir dipivoxil (ADV) in a patient with chronic hepatitis B.


RESULTS
Successful suppression of hepatitis B virus (HBV) replication by sequential therapy of 9 MU thrice weekly interferon (IFN) and 3TC was followed by genotypical resistance detected at month 28 of therapy (month 19 of lamivudine treatment). ADV was added to 3TC therapy on month 44 of antiviral treatment. Neither alanine aminotransferase normalization nor a stable decrease in HBV viral load was observed, although ADV was used for more than 40 months. The HBV pol region was amplified from serum samples obtained before and after ADV treatment. The complete genome was cloned into a TA vector. PCR products and 7-10 clones from each cloned vector were sequenced. A novel mutation, A181S, in the reverse transcriptase gene leading to a conversion of W172C in the overlapping surface antigen gene was detected along with a M2041 mutation. The complete genome comprising the A181S+M2041 pattern was cloned into an expression vector and its in vitro susceptibility to 3TC, ADV, tenofovir (PMPA), clevudine (L-FMAU) and emtricitabine (FTC) were determined in transiently transfected Huh7 cells. This mutation pattern displayed more than 1000-fold resistance to the nucleoside analogues 3TC and FTC and approximately sixfold resistance to L-FMAU, while it confers 28.23- and 5.57-fold resistance for the nucleotide analogues ADV and PMPA, respectively.


CONCLUSIONS
A new mutation pattern, A181S+M2041, arising under lamivudine treatment confers cross-resistance to ADV both in vivo and in vitro.
Karatayli
Ersin
E
Institute of Hepatology, Ankara University, Ankara, Turkey.
Karayalçin
Selim
S
Karaaslan
Hayri
H
Kayhan
Handan
H
Türkyilmaz
A Resat
AR
Sahin
Fikret
F
Yurdaydin
Cihan
C
Bozdayi
A Mithat
AM
D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D000328:Adult; D001086:Arabinofuranosyluracil / Q000031:analogs & derivatives / Q000494:pharmacology; D001483:Base Sequence; D045744:Cell Line, Tumor; D003001:Cloning, Molecular; D004252:DNA Mutational Analysis; D004279:DNA, Viral / Q000097:blood; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D024921:Drug Resistance, Multiple, Viral / Q000235:genetics*; D000068679:Emtricitabine; D006515:Hepatitis B virus / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D019694:Hepatitis B, Chronic / Q000097:blood / Q000188:drug therapy* / Q000235:genetics; D006801:Humans; D019259:Lamivudine / Q000494:pharmacology / Q000627:therapeutic use*; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D063065:Organophosphonates / Q000494:pharmacology / Q000627:therapeutic use*; D012194:RNA-Directed DNA Polymerase / Q000235:genetics* / Q000378:metabolism; D018894:Reverse Transcriptase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D000068698:Tenofovir; D013997:Time Factors; D014162:Transfection; D016896:Treatment Outcome; D019562:Viral Load; D014779:Virus Replication / Q000187:drug effects
D004279:DNA, Viral; D063065:Organophosphonates; D018894:Reverse Transcriptase Inhibitors; D003841:Deoxycytidine; D019259:Lamivudine; D001086:Arabinofuranosyluracil; D000068698:Tenofovir; D012194:RNA-Directed DNA Polymerase; D000068679:Emtricitabine; C034935:clevudine; D000225:Adenine; C106812:adefovir dipivoxil