Characterization of HIV isolates arising after prolonged zidovudine therapy

Douglas L. Mayers, Francine E. McCutchan, Eric E. Sanders-Buell, Linda I. Merritt, Sonya Dilworth, Arnold K. Fowler, Christopher A. Marks, Nancy M. Ruiz, Douglas D. Richman, Chester R. Roberts, Donald S. Burke

Research output: Contribution to journalArticlepeer-review


Human immunodeficiency virus type 1 (HIV-1) was isolated from five patients with late-stage disease treated with zidovudine (ZDV) for more than 1 year. Peripheral blood mononuclear cells (PBMCs) were used for all virus isolations and to assay for drug resistance. The isolates exhibited a 10- to 100-fold decrease in ZDV susceptibility compared to pretreatment isolates. Multiple clones of a 618 bp segment of the HIV reverse transcriptase gene encompassing codons 60-250 were sequenced for each isolate. The association of alterations at codons Asp67 → Asn, Lys70 → Arg, Thr215 → Phe or Tyr, and Lys219 → Gln with ZDV resistance has been previously noted (ref. 5). In this study, the most frequent alteration was Thr215 → Tyr although genotypic mixtures of Thr/Tyr and Phe/Tyr were also observed. One isolate with a Tyr215 alteration and unaltered codons at 67, 70, and 219 had high-level ZDV resistance. Alterations at codons 67, 70, and 219 did not appear to increase resistance when seen in combination with Tyr215. Virus isolates obtained from each patient by cultivation with either 0 or 4 μM ZDV were compared and found to have similar alterations at codons 67, 70, 215, and 219, although one instance of apparent in vitro selection for Tyr215 over Phe215 was observed. Assays using PBMCs for virus propagation will permit susceptibility testing of HIV isolates from most patients on antiretroviral drugs to investigate the clinical significance of drug resistance.

Original languageEnglish (US)
Pages (from-to)749-759
Number of pages11
JournalJournal of Acquired Immune Deficiency Syndromes
Issue number8
StatePublished - Aug 1992


  • DNA sequence
  • Reverse transcriptase
  • Susceptibility assay
  • Zidovudine resistance

ASJC Scopus subject areas

  • Infectious Diseases
  • Pharmacology (medical)


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