title: Development of HIV-1 resistance to (-)2'-deoxy-3'-thiacytidine in patients with AIDS or advanced AIDS-related complex.
abstract: OBJECTIVE
  To determine the rate of development of in vitro HIV resistance to (-)2'-deoxy-3'-thiacytidine (3TC) and relate the effect of dose to emergence of resistance.
  
  
  METHODS
  HIV-infected men and non-pregnant women, aged > or = 18 years, with a CD4 count < or = 300 x 10(6)/l cells were followed in a Phase I/II study, in which they were evaluated for tolerance to 3TC and effect of this agent with regard to viral susceptibility. Peripheral blood and plasma samples were collected at regular intervals for analysis. HIV was isolated using umbilical cord blood mononuclear cells as targets. These cells were also used in determinations of median inhibitory drug concentration. Specific amplification of the 184 mutation site, associated with HIV resistance to 3TC, was performed by polymerase chain reaction, using specific primer pairs, on DNA harvested from infected peripheral blood mononuclear cells (PBMC) of donors or, alternatively, on DNA that had been reverse transcribed from plasma-associated HIV RNA.
  
  
  RESULTS
  Phenotypic resistance was detected in approximately one-third of individuals studied, who were followed between 8 and 56 weeks. Development of 3TC resistance occurred independently of dose, although time of first appearance of resistant HIV-1 variants appeared reduced at high 3TC doses. Amino-acid changes at codon 184 in HIV-1 reverse transcriptase were associated with, and preceded, the development of phenotypic 3TC resistance. Most commonly, a Met to Ile substitution appeared transiently before being superceded by a Val substitution at codon 184.
  
  
  CONCLUSIONS
  In vitro resistance to 3TC developed in a high proportion of subjects who received prolonged monotherapy with this drug. The development of resistance to 3TC was associated with appearance of mutated viral forms and the disappearance of wild-type virus, with regard to codon 184, in both patient plasma and PBMC.
authors.affiliation: McGill University AIDS Centre, Jewish General Hospital, Montreal, Quebec, Canada.
authors.forename: M A
authors.initials: MA
authors.lastname: Wainberg
authors.forename: H
authors.initials: H
authors.lastname: Salomon
authors.forename: Z
authors.initials: Z
authors.lastname: Gu
authors.forename: J S
authors.initials: JS
authors.lastname: Montaner
authors.forename: T P
authors.initials: TP
authors.lastname: Cooley
authors.forename: R
authors.initials: R
authors.lastname: McCaffrey
authors.forename: J
authors.initials: J
authors.lastname: Ruedy
authors.forename: H M
authors.initials: HM
authors.lastname: Hirst
authors.forename: N
authors.initials: N
authors.lastname: Cammack
authors.forename: J
authors.initials: J
authors.lastname: Cameron
mesh_terms: D000386:AIDS-Related Complex / Q000188:drug therapy* / Q000821:virology; D000163:Acquired Immunodeficiency Syndrome / Q000188:drug therapy* / Q000821:virology; D000293:Adolescent; D000328:Adult; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D004352:Drug Resistance, Microbial / Q000235:genetics; D005260:Female; D054303:HIV Reverse Transcriptase; D015497:HIV-1 / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D006801:Humans; D066298:In Vitro Techniques; D019259:Lamivudine; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D011533:Proviruses / Q000187:drug effects / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics; D018894:Reverse Transcriptase Inhibitors; D013997:Time Factors; D016047:Zalcitabine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D017931:DNA Primers; D012367:RNA, Viral; D018894:Reverse Transcriptase Inhibitors; D019259:Lamivudine; D016047:Zalcitabine; D054303:HIV Reverse Transcriptase