title: The R263K substitution in HIV-1 subtype C is more deleterious for integrase enzymatic function and viral replication than in subtype B.
abstract: OBJECTIVE
  Dolutegravir is an integrase strand-transfer inhibitor that has shown unprecedented robustness against the emergence of HIV drug-resistant strains in treatment-naive individuals. The R263K substitution in integrase was identified through culture selection as a resistance-associated substitution for dolutegravir and was recently detected in two treatment-experienced participants in the SAILING clinical trial, who experienced dolutegravir-based treatment failure, one of whom was infected by a subtype C virus. The objective of this study was to characterize the R263K substitution in HIV-1 subtype C integrase.
  
  
  METHODS
  We used cell-free strand transfer assays and tissue culture experiments to characterize the R263K substitution in HIV-1 subtype C integrase in comparison with subtype B.
  
  
  RESULTS
  Cell-free biochemical assays showed that the R263K substitution diminished subtype C integrase strand-transfer activity by decreasing the affinity of integrase for target DNA. Similarly, both viral infectiousness and replication capacity were reduced by the R263K substitution in tissue culture. Decrease in enzyme activity and viral infectiousness exceeded 35 and 50%, respectively - significantly more than in HIV-1 subtype B. R263K in HIV-1 subtype C also conferred low levels of resistance against dolutegravir and high levels of cross-resistance against elvitegravir, but not raltegravir.
  
  
  CONCLUSIONS
  The R263K substitution is more deleterious to integrase strand-transfer activity and viral infectiousness in HIV-1 subtype C than in subtype B. Our results suggest that cross-resistance may prevent treatment-experienced individuals who are experiencing treatment failure with dolutegravir from being subsequently treated with elvitegravir.
authors.affiliation: aMcGill University AIDS Centre, Lady Davis Institute for Medical Research, Jewish General Hospital bDivision of Experimental Medicine cDepartment of Microbiology and Immunology, Faculty of Medicine, McGill University, Montréal, Québec, Canada. *Thibault Mesplède and Peter K. Quashie contributed equally to the writing of this article.
authors.forename: Thibault
authors.initials: T
authors.lastname: Mesplède
authors.forename: Peter K
authors.initials: PK
authors.lastname: Quashie
authors.forename: Said
authors.initials: S
authors.lastname: Hassounah
authors.forename: Nathan
authors.initials: N
authors.lastname: Osman
authors.forename: Yingshan
authors.initials: Y
authors.lastname: Han
authors.forename: Jiaming
authors.initials: J
authors.lastname: Liang
authors.forename: Diane N
authors.initials: DN
authors.lastname: Singhroy
authors.forename: Mark A
authors.initials: MA
authors.lastname: Wainberg
mesh_terms: D019943:Amino Acid Substitution; D019380:Anti-HIV Agents / Q000494:pharmacology; D001669:Biochemical Phenomena; D002460:Cell Line; D024882:Drug Resistance, Viral; D005838:Genotype; D019427:HIV Integrase / Q000235:genetics* / Q000378:metabolism*; D015497:HIV-1 / Q000145:classification / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D006575:Heterocyclic Compounds, 3-Ring / Q000494:pharmacology; D006801:Humans; D020125:Mutation, Missense; D010078:Oxazines; D010879:Piperazines; D011728:Pyridones; D012641:Selection, Genetic; D014776:Virus Cultivation; D014779:Virus Replication; D000099226:Dolutegravir
chemical_list: D019380:Anti-HIV Agents; D019427:HIV Integrase; D006575:Heterocyclic Compounds, 3-Ring; D010078:Oxazines; D010879:Piperazines; D011728:Pyridones; D000099226:Dolutegravir; C514801:p31 integrase protein, Human immunodeficiency virus 1