title: HIV-1 protease mutation 82M contributes to phenotypic resistance to protease inhibitors in subtype G.
abstract: OBJECTIVE
  The purpose of this study was the qualitative and quantitative assessment of the in vitro effect of HIV-1 protease (PR) mutation 82M on replication capacity and susceptibility to the eight clinically available PR inhibitors (PIs).
  
  
  METHODS
  The 82M substitution was introduced by site-directed mutagenesis in wild-type subtype B and G strains, as well as reverted back to wild-type in a therapy-failing strain. The recombinant viruses were evaluated for their replication capacity and susceptibility to PIs.
  
  
  RESULTS
  The single 82M mutation within a wild-type subtype B or G background did not result in drug resistance. However, the in vitro effect of single PR mutations on PI susceptibility is not always distinguishable from wild-type virus, and particular background mutations and polymorphisms are required to detect significant differences in the drug susceptibility profile. Consequently, reverting the 82M mutation back to wild-type (82I) in a subtype G isolate from a patient that failed therapy with multiple other PR mutations did result in significant increases in susceptibility towards indinavir and lopinavir and minor increases in susceptibility towards amprenavir and atazanavir. The presence of the 82M mutation also slightly decreased viral replication, whether it was in the genetic background of subtype B or subtype G.
  
  
  CONCLUSIONS
  Our results suggest that 82M has an impact on PI susceptibility and that this effect is not due to a compensatory effect on the replication capacity. Because 82M is not observed as a polymorphism in any subtype, these observations support the inclusion of 82M in drug resistance interpretation systems and PI mutation lists.
authors.affiliation: Clinical and Epidemiological Virology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, Leuven, Belgium. acmpalma@gmail.com
authors.forename: Ana Carolina
authors.initials: AC
authors.lastname: Palma
authors.forename: Kris
authors.initials: K
authors.lastname: Covens
authors.forename: Joke
authors.initials: J
authors.lastname: Snoeck
authors.forename: Anne-Mieke
authors.initials: AM
authors.lastname: Vandamme
authors.forename: Ricardo Jorge
authors.initials: RJ
authors.lastname: Camacho
authors.forename: Kristel
authors.initials: K
authors.lastname: Van Laethem
mesh_terms: D019943:Amino Acid Substitution; D019380:Anti-HIV Agents / Q000494:pharmacology*; D024882:Drug Resistance, Viral; D016333:HIV Protease / Q000235:genetics* / Q000378:metabolism*; D017320:HIV Protease Inhibitors / Q000494:pharmacology*; D015497:HIV-1 / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D006801:Humans; D008826:Microbial Sensitivity Tests; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D014779:Virus Replication / Q000187:drug effects
chemical_list: D019380:Anti-HIV Agents; D017320:HIV Protease Inhibitors; D050505:Mutant Proteins; D016333:HIV Protease; C514803:p16 protease, Human immunodeficiency virus 1