title: Drug resistance mutations during structured treatment interruptions.
abstract: BACKGROUND
  We assessed whether treatment interruptions induce selection of mutations associated with drug resistance in the Swiss-Spanish Intermittent Treatment Trial (SSITT). Patients had been on HAART without previous failure and had undetectable viraemia for at least 6 months. Their HAART was interrupted for 2 weeks and restarted for 8 weeks. After four of these cycles, treatment was definitively interrupted at week 40.
  
  
  METHODS
  Genotypic resistance testing was performed in 87/97 Swiss patients: in those failing treatment before week 40, at the time of first viral rebound > 500 copies/ml off treatment and preceding failure to reach RNA < 50 copies/ml after 8 weeks of re-treatment; for patients without virological failure, on the first sample with HIV-1 RNA > 1000 copies/ml after week 40.
  
  
  RESULTS
  Mutations associated with drug resistance were detected in 9/25 (36%) patients with virological failure during the first 40 weeks and in 6/59 (10%) patients after week 40. Overall, drug resistance mutations were detected in 17% of patients, all but two with the 184V/I mutation. Among the 74 patients receiving lamivudine, the M184V/I mutation was detected in 13/74 (17.6%) patients. A wild-type codon at position 184 was detected in previous samples in all but two. The relative risk for virological failure was 2.55-fold higher in patients with the M184V/I mutation than in patients without detectable mutation (P=0.007).
  
  
  CONCLUSIONS
  The M184V/I mutation is frequently selected during repeated treatment interruptions.
authors.affiliation: Laboratory of Virology, Geneva University Hospital, Switzerland.
authors.forename: Sabine
authors.initials: S
authors.lastname: Yerly
authors.forename: Catherine
authors.initials: C
authors.lastname: Fagard
authors.forename: Huldrych F
authors.initials: HF
authors.lastname: Günthard
authors.forename: Bernard
authors.initials: B
authors.lastname: Hirschel
authors.forename: Luc
authors.initials: L
authors.lastname: Perrin
mesh_terms: D019380:Anti-HIV Agents / Q000008:administration & dosage* / Q000494:pharmacology / Q000627:therapeutic use; D023241:Antiretroviral Therapy, Highly Active; D004334:Drug Administration Schedule; D024882:Drug Resistance, Viral / Q000235:genetics*; D015658:HIV Infections / Q000188:drug therapy* / Q000821:virology; D016333:HIV Protease / Q000235:genetics; D054303:HIV Reverse Transcriptase / Q000235:genetics; D015497:HIV-1 / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D006801:Humans; D019259:Lamivudine / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D008826:Microbial Sensitivity Tests; D009154:Mutation; D012367:RNA, Viral / Q000097:blood; D018894:Reverse Transcriptase Inhibitors / Q000008:administration & dosage* / Q000494:pharmacology / Q000627:therapeutic use
chemical_list: D019380:Anti-HIV Agents; D012367:RNA, Viral; D018894:Reverse Transcriptase Inhibitors; D019259:Lamivudine; D054303:HIV Reverse Transcriptase; D016333:HIV Protease