title: Genotypic/phenotypic patterns of HIV-1 integrase resistance to raltegravir.
abstract: OBJECTIVE
  To understand the dynamic viral evolution observed during failure on raltegravir-containing regimens, we studied the genotypic and phenotypic patterns of resistance to raltegravir and the residual replication capacity (rRC) of HIV-1 variants selected in vivo.
  
  
  METHODS
  Clonal genotypic analyses were performed on sequential HIV-1 integrase sequences amplified from 11 failing patients and sampled every 4-24 weeks for up to 64 weeks. Fully replicating recombinant viruses were generated using modified vectors in which selected viral integrase genes amplified from patients' plasma were cloned. rRC was measured by a novel multiple cycle competition assay. Resistance to raltegravir and the rRC of resistant HIV-1 variants selected in vivo were evaluated in purified CD4+ T cells.
  
  
  RESULTS
  In all of the patients but one, failure was associated with selection of mutations in positions 143, 148 or 155. Unlike mutations at position 143 (Y143S/K/R), identified alone or in combination with others, mutations at position 148 and 155 were always found in combination. A wide range of resistance levels to raltegravir [from 10- to 770-fold change in 50% inhibitory concentration (IC(50)) compared with baseline] was observed using recombinant viral clones. Finally, rRC was not significantly altered in highly resistant variants.
  
  
  CONCLUSIONS
  Two patterns of viral evolution were observed in the resistant viral populations, driving the variants towards a fast (most of them with G140S + Q148H mutations) or progressive increase in resistance to raltegravir. These results may have implications either for the evaluation of genotypic results, or for the correct clinical use of the compound.
authors.affiliation: Università Vita-Salute San Raffaele, Milano, Italy. canducci.filippo@hsr.it
authors.forename: Filippo
authors.initials: F
authors.lastname: Canducci
authors.forename: Maria Chiara
authors.initials: MC
authors.lastname: Marinozzi
authors.forename: Michela
authors.initials: M
authors.lastname: Sampaolo
authors.forename: Enzo
authors.initials: E
authors.lastname: Boeri
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Spagnuolo
authors.forename: Nicola
authors.initials: N
authors.lastname: Gianotti
authors.forename: Antonella
authors.initials: A
authors.lastname: Castagna
authors.forename: Stefania
authors.initials: S
authors.lastname: Paolucci
authors.forename: Fausto
authors.initials: F
authors.lastname: Baldanti
authors.forename: Adriano
authors.initials: A
authors.lastname: Lazzarin
authors.forename: Massimo
authors.initials: M
authors.lastname: Clementi
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D019380:Anti-HIV Agents / Q000494:pharmacology*; D015496:CD4-Positive T-Lymphocytes / Q000821:virology; D002478:Cells, Cultured; D024882:Drug Resistance, Viral; D005838:Genotype; D015658:HIV Infections / Q000188:drug therapy / Q000821:virology*; D019427:HIV Integrase / Q000235:genetics*; D015497:HIV-1 / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D006801:Humans; D020128:Inhibitory Concentration 50; D008826:Microbial Sensitivity Tests; D020125:Mutation, Missense; D010641:Phenotype; D011760:Pyrrolidinones / Q000494:pharmacology*; D000068898:Raltegravir Potassium; D017422:Sequence Analysis, DNA; D014779:Virus Replication
chemical_list: D019380:Anti-HIV Agents; D011760:Pyrrolidinones; D000068898:Raltegravir Potassium; D019427:HIV Integrase; C514801:p31 integrase protein, Human immunodeficiency virus 1