title: Mutation Q95K enhances N155H-mediated integrase inhibitor resistance and improves viral replication capacity.
abstract: OBJECTIVE
  The genetic barrier to development of raltegravir resistance is considered to be low, requiring at least one primary integrase mutation: Y143C, Q148H/K/R or N155H to confer raltegravir therapy failure. However, during continued raltegravir treatment failure, additional mutations may be selected. In a patient failing raltegravir therapy, we investigated the impact of multiple integrase mutations on resistance and viral replication. Furthermore, in vivo fitness was investigated during failure of raltegravir-containing highly active antiretroviral therapy and after raltegravir was discontinued from the regimen.
  
  
  METHODS
  Patient-derived viral integrase genes were cloned into a reference strain. These recombinant viruses were used to determine the contribution of individual integrase mutations to raltegravir resistance and replication capacity in vitro. To determine in vivo fitness, the relative proportion of specific integrase mutations was monitored over time by in-depth clonal analysis of the viral integrase at baseline, during and after raltegravir treatment.
  
  
  RESULTS
  Raltegravir therapy failure was associated with the initial selection of primary resistance mutation N155H. This mutation conferred a 3.8-fold reduction in raltegravir susceptibility and a severe reduction in viral replication. Acquisition of integrase mutation Q95K increased resistance (6.2-fold) and partly restored viral replication. Selection of a third mutation, V151I, further increased raltegravir resistance (20-fold), but decreased viral replication. After prolonged raltegravir interruption, raltegravir resistance mutations were lost, demonstrating the reduced replication capacity of the resistant virus.
  
  
  CONCLUSIONS
  We describe selection of Q95K as a secondary resistance mutation during raltegravir therapy failure. In the background of N155H, Q95K enhances raltegravir and elvitegravir resistance and improves the impaired replication of the virus.
authors.affiliation: Department of Virology, Medical Microbiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Axel
authors.initials: A
authors.lastname: Fun
authors.forename: Kurt
authors.initials: K
authors.lastname: Van Baelen
authors.forename: Steven F L
authors.initials: SF
authors.lastname: van Lelyveld
authors.forename: Pauline J
authors.initials: PJ
authors.lastname: Schipper
authors.forename: Lieven J
authors.initials: LJ
authors.lastname: Stuyver
authors.forename: Annemarie M J
authors.initials: AM
authors.lastname: Wensing
authors.forename: Monique
authors.initials: M
authors.lastname: Nijhuis
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D019380:Anti-HIV Agents / Q000627:therapeutic use; D023241:Antiretroviral Therapy, Highly Active / Q000379:methods; D024882:Drug Resistance, Viral; D019143:Evolution, Molecular; D015658:HIV Infections / Q000188:drug therapy / Q000821:virology; D019427:HIV Integrase / Q000235:genetics*; D019428:HIV Integrase Inhibitors / Q000494:pharmacology*; D015497:HIV-1 / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology; D006801:Humans; D020125:Mutation, Missense; D012641:Selection, Genetic; D017211:Treatment Failure; D019562:Viral Load; D014779:Virus Replication
chemical_list: D019380:Anti-HIV Agents; D019428:HIV Integrase Inhibitors; D019427:HIV Integrase; C514801:p31 integrase protein, Human immunodeficiency virus 1