title: Natural occurrence of drug resistance mutations in the reverse transcriptase of human immunodeficiency virus type 1 isolates.
abstract: Reverse transcriptase-associated amino acid substitutions related to ddC, d4T, and nevirapine resistance have been found in isolates of human immunodeficiency virus type 1 (HIV-1) from patients treated with AZT only. Sequence analysis of 23 isolates documented the presence of 4 unexpected mutations at amino acid residues related to drug resistance. Two isolates contained an aspartic residue in codon 69 associated with ddC resistance, and another a change in codon 75 associated with resistance to d4T. The Y-to-C alteration in codon 181 associated with nevirapine resistance was observed in another isolate after serial passage in cell culture in the absence of drug. Changes in substitution patterns were also noted after serial passage of four AZT resistant isolates in cell culture without inhibitors. One of the strains showed changes in codons 67 and 70 to wild-type residues. Clonal analysis showed that this alteration occurred by the selection during cell culture passage of the wild-type genotype, which was present as a minority subpopulation in the initially resistant virus stock, rather than to genetic reversion. In summary, we present evidence documenting the presence of mutations associated with drug resistance in the absence of drug treatment and supporting the role played by gentic variability in the emergence of HIV-1 antiviral resistance.
authors.affiliation: Centro Nacional de Biologia Celular y Retrovirus, Instituto de Salud Carlos III, Madrid, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Nájera
authors.forename: D D
authors.initials: DD
authors.lastname: Richman
authors.forename: I
authors.initials: I
authors.lastname: Olivares
authors.forename: J M
authors.initials: JM
authors.lastname: Rojas
authors.forename: M A
authors.initials: MA
authors.lastname: Peinado
authors.forename: M
authors.initials: M
authors.lastname: Perucho
authors.forename: R
authors.initials: R
authors.lastname: Nájera
authors.forename: C
authors.initials: C
authors.lastname: López-Galíndez
mesh_terms: D000595:Amino Acid Sequence; D000998:Antiviral Agents / Q000494:pharmacology; D001483:Base Sequence; D003001:Cloning, Molecular; D004279:DNA, Viral / Q000235:genetics; D004352:Drug Resistance, Microbial / Q000235:genetics; D054303:HIV Reverse Transcriptase; D015497:HIV-1 / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D019829:Nevirapine; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D011725:Pyridines / Q000494:pharmacology; D012194:RNA-Directed DNA Polymerase / Q000235:genetics*; D018894:Reverse Transcriptase Inhibitors; D018119:Stavudine / Q000494:pharmacology; D014776:Virus Cultivation; D016047:Zalcitabine / Q000494:pharmacology; D015215:Zidovudine / Q000494:pharmacology
chemical_list: D000998:Antiviral Agents; D004279:DNA, Viral; D011725:Pyridines; D018894:Reverse Transcriptase Inhibitors; D015215:Zidovudine; D016047:Zalcitabine; D019829:Nevirapine; D018119:Stavudine; D054303:HIV Reverse Transcriptase; D012194:RNA-Directed DNA Polymerase