title: In vitro analysis of human immunodeficiency virus type 1 resistance to nevirapine and fitness determination of resistant variants.
abstract: Nevirapine-resistant variants were generated by serial passages in MT-2 cells in the presence of increasing drug concentrations. In passage 5, mutations V106A, Y181C and G190A were detected in the global population, associated with a 100-fold susceptibility decrease. Sequence analysis of biological clones obtained from passage 5 and subsequent passages showed that single mutants, detected in first passages, were progressively replaced in passage 15 by double mutants, correlating with a 500-fold increase in phenotypic resistance. Fitness determination of single mutants confirmed that, in the presence of nevirapine, every variant was more fit than wild-type with a fitness order Y181C>V106A>G190A>wild-type. Unexpectedly, in the absence of the drug, the Y181C resistant mutant was more fit than wild-type, with a fitness gradient Y181C>wild-type >G106A>or=V190A. Using a molecular clone in which the Y181C mutation was introduced by in vitro mutagenesis, the greater fitness of the Y181C mutant was confirmed in new competition cultures. These data exemplify the role of resistance mutations on virus phenotype but also on virus evolution leading, occasionally, to resistant variants fitter than the wild-type in the absence of the drug.
authors.affiliation: Servicio de Virología Molecular, Centro Nacional de Biología Fundamental, Instituto de Salud Carlos III, Carretera Majadahonda-Pozuelo Km. 2, Majadahonda, 28220 Madrid, Spain1.
authors.forename: Maria Dolores
authors.initials: MD
authors.lastname: Iglesias-Ussel
authors.affiliation: Servicio de Virología Molecular, Centro Nacional de Biología Fundamental, Instituto de Salud Carlos III, Carretera Majadahonda-Pozuelo Km. 2, Majadahonda, 28220 Madrid, Spain1.
authors.forename: Concepción
authors.initials: C
authors.lastname: Casado
authors.affiliation: Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain2.
authors.forename: Eloísa
authors.initials: E
authors.lastname: Yuste
authors.affiliation: Servicio de Virología Molecular, Centro Nacional de Biología Fundamental, Instituto de Salud Carlos III, Carretera Majadahonda-Pozuelo Km. 2, Majadahonda, 28220 Madrid, Spain1.
authors.forename: Isabel
authors.initials: I
authors.lastname: Olivares
authors.affiliation: Servicio de Virología Molecular, Centro Nacional de Biología Fundamental, Instituto de Salud Carlos III, Carretera Majadahonda-Pozuelo Km. 2, Majadahonda, 28220 Madrid, Spain1.
authors.forename: Cecilio
authors.initials: C
authors.lastname: López-Galíndez
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D019380:Anti-HIV Agents / Q000494:pharmacology*; D024882:Drug Resistance, Viral / Q000235:genetics*; D014644:Genetic Variation; D005838:Genotype; D015497:HIV-1 / Q000187:drug effects / Q000235:genetics*; D006367:HeLa Cells; D006801:Humans; D019829:Nevirapine / Q000494:pharmacology*; D010641:Phenotype; D018894:Reverse Transcriptase Inhibitors / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D019380:Anti-HIV Agents; D018894:Reverse Transcriptase Inhibitors; D019829:Nevirapine