title: Analysis of HIV cross-resistance to protease inhibitors using a rapid single-cycle recombinant virus assay for patients failing on combination therapies.
abstract: OBJECTIVE
  To assess the patterns of HIV phenotypic cross-resistance to protease inhibitors (PI) in patients experiencing viral load rebound on combination therapy including a PI.
  
  
  METHODS
  Phenotypic analysis of sensitivity to indinavir, nelfinavir, saquinavir, ritonavir and amprenavir was carried out using a single-cycle recombinant virus assay. Viral protease was sequenced by automated dideoxynucleotide chain termination.
  
  
  RESULTS
  Of the 108 patients studied, 68 had received indinavir, 50 ritonavir, 25 saquinavir and eight nelfinavir. The majority (71%) had received only one PI. The incidence of cross-resistance between indinavir, nelfinavir, ritonavir and saquinavir was high (60-90%). Cross-resistance to amprenavir was less frequent (37-40%). However there was some correlation between levels of sensitivity to amprenavir and indinavir (r2 = 0.34; P < 0.01). Conversely, the correlation between levels of sensitivity to indinavir and saquinavir was poor (r2 = 0.25), particularly for patients who had not received saquinavir. The degree of cross-resistance correlated with the level of resistance and with the total number of mutations in the protease gene (P < 0.05, chi square test) but could not be significantly correlated to any one particular mutation or combination of mutations. Mutation 184V was significantly associated with cross-resistance to amprenavir, with no mutations at codon 50 observed, while mutations associated with cross-resistance to saquinavir differed according to the treatment received.
  
  
  CONCLUSIONS
  These results suggest that, although the total number of protease mutations correlates with the degree of cross-resistance, the specific mechanisms accounting for primary resistance and for cross-resistance may be different.
authors.affiliation: Laboratoire de Recherche Antivirale, Hôpital Bichat-Claude Bernard, Paris, France.
authors.forename: E
authors.initials: E
authors.lastname: Race
authors.forename: E
authors.initials: E
authors.lastname: Dam
authors.forename: V
authors.initials: V
authors.lastname: Obry
authors.forename: S
authors.initials: S
authors.lastname: Paulous
authors.forename: F
authors.initials: F
authors.lastname: Clavel
mesh_terms: D019380:Anti-HIV Agents / Q000494:pharmacology* / Q000627:therapeutic use; D004352:Drug Resistance, Microbial / Q000235:genetics; D018432:Drug Resistance, Multiple / Q000235:genetics; D004359:Drug Therapy, Combination; D005838:Genotype; D015658:HIV Infections / Q000188:drug therapy / Q000821:virology*; D016333:HIV Protease / Q000235:genetics*; D017320:HIV Protease Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D015497:HIV-1 / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D006801:Humans; D010641:Phenotype; D017211:Treatment Failure
chemical_list: D019380:Anti-HIV Agents; D017320:HIV Protease Inhibitors; D016333:HIV Protease