title: Stepwise process for the development of entecavir resistance in a chronic hepatitis B virus infected patient.
abstract: OBJECTIVE
  Complex mutants may be selected under sequential anti-VHB pressures. We analyzed the genotypic and phenotypic evolution of the viral quasi-species of a patient who developed resistance to entecavir following lamivudine breakthrough.
  
  
  METHODS
  The polymerase gene was amplified, cloned and sequenced at different time points. Hepatoma cell lines were transfected to compare the replication capacity of HBV mutants and their drug susceptibility.
  
  
  RESULTS
  A mixture of lamivudine-resistant HBV strains coexisted following viral breakthrough to lamivudine, all harboring the rtM204V mutation. The rtV173L+L180M+M204V dominant mutant displayed strong lamivudine-resistance and the highest replication capacity. Following the switch to entecavir, the viral load dropped but the lamivudine-resistant strains continued to be selected. Three years later, the viral load rose again, and a complex mixture of entecavir-resistant strains, all harboring the lamivudine-resistance signature rtL180M+M204V and the rtS202G mutation were observed. Although the rtL180M+S202G+M204V variant, that prevailed at the end of entecavir therapy, did not show the highest viral genome replication capacity, it conferred one of the strongest resistance levels to entecavir.
  
  
  CONCLUSIONS
  We report the selection of complex HBV mutants that escaped lamivudine and entecavir antiviral pressures. Genotypic and phenotypic analysis provided additional information to understand the process of HBV variant selection.
authors.affiliation: INSERM, U271, Laboratoire des virus hépatiques et pathologies associées, Lyon F-69003, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Villet
authors.forename: Aurélie
authors.initials: A
authors.lastname: Ollivet
authors.forename: Christian
authors.initials: C
authors.lastname: Pichoud
authors.forename: Luc
authors.initials: L
authors.lastname: Barraud
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Villeneuve
authors.forename: Christian
authors.initials: C
authors.lastname: Trépo
authors.forename: Fabien
authors.initials: F
authors.lastname: Zoulim
mesh_terms: D000368:Aged; D000998:Antiviral Agents / Q000494:pharmacology*; D024882:Drug Resistance, Viral / Q000235:genetics*; D006147:Guanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006515:Hepatitis B virus / Q000187:drug effects / Q000235:genetics*; D019694:Hepatitis B, Chronic / Q000188:drug therapy*; D006801:Humans; D019259:Lamivudine / Q000627:therapeutic use; D008297:Male; D009154:Mutation / Q000235:genetics
chemical_list: D000998:Antiviral Agents; D019259:Lamivudine; C413685:entecavir; D006147:Guanine