title: HIV with reduced sensitivity to zidovudine (AZT) isolated during prolonged therapy.
abstract: The drug sensitivities of human immunodeficiency virus (HIV) isolates from a group of patients with acquired immunodeficiency syndrome (AIDS) or AIDS-related complex (ARC) who were receiving zidovudine (3'-azido-3'-deoythymidine, AZT) therapy were tested by means of a newly developed plaque assay in CD4+ HeLa cells. Fifty percent inhibitory dose (ID50) values of 18 isolates from untreated individuals ranged between 0.01 microM and 0.05 microM. In contrast, most isolates from patients who had received zidovudine for 6 months or more exhibited decreased sensitivity characterized by changes in ID50 or ID95 values (or both), with isolates from several patients (5/15) showing 100-fold increases in ID50. The latter isolates were also insensitive to 3'-azido-2',3'-dideoxyuridine; however, the isolates were still sensitive to 2',3'-dideoxycytidine, 2',3'-dideoxy-2',3'-didehydrothymidine, or phosphonoformate. It cannot be determined from this small sample of patients whether development of a less sensitive virus phenotype results in clinical resistance. Appearance of such variants was not associated with a consistent increase in viral p24 concentrations in patient plasma and did not herald any sudden deterioration in clinical status. More extensive studies are required to determine the clinical significance. Thus, it would be premature to alter any treatment protocols for HIV-infected individuals at present.
authors: Molecular Sciences, Wellcome Research Laboratories, Beckenham, Kent BR3 3BS, United Kingdon.
authors: B A
authors: BA
authors: Larder
authors: G
authors: G
authors: Darby
authors: D D
authors: DD
authors: Richman
mesh_terms: D000386:AIDS-Related Complex / Q000188:drug therapy / Q000382:microbiology; D000163:Acquired Immunodeficiency Syndrome / Q000188:drug therapy / Q000382:microbiology*; D015224:Dideoxynucleosides / Q000494:pharmacology; D004351:Drug Resistance; D017245:Foscarnet; D006678:HIV / Q000187:drug effects* / Q000276:immunology / Q000302:isolation & purification; D016655:HIV Core Protein p24; D006367:HeLa Cells; D006801:Humans; D008826:Microbial Sensitivity Tests; D010746:Phosphonoacetic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D012191:Retroviridae Proteins / Q000032:analysis; D018894:Reverse Transcriptase Inhibitors; D010948:Viral Plaque Assay; D014779:Virus Replication / Q000187:drug effects; D016047:Zalcitabine / Q000031:analogs & derivatives; D015215:Zidovudine / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: D015224:Dideoxynucleosides; D016655:HIV Core Protein p24; D012191:Retroviridae Proteins; D018894:Reverse Transcriptase Inhibitors; D017245:Foscarnet; D015215:Zidovudine; D016047:Zalcitabine; C050624:2',3'-dideoxycytidinene; D010746:Phosphonoacetic Acid