title: Natural polymorphisms in the protease gene modulate the replicative capacity of non-B HIV-1 variants in the absence of drug pressure.
abstract: BACKGROUND
  Genetic variation in the HIV-1 pol gene, which encodes the main targets for anti-HIV drugs, may favors different susceptibility and resistance pathways to antiretroviral agents. Several amino acid substitutions occur frequently in some non-B viruses at positions associated with drug resistance in clade B viruses. The clinical relevance of those polymorphisms is unclear.
  
  
  OBJECTIVE
  To evaluate the effect of two natural protease (PR) polymorphisms, K20I and M36I, which are frequently found in non-B subtypes, on the virus replicative capacity in the presence and absence of protease inhibitors (PI).
  
  
  METHODS
  Infectious HIV-1 clones carrying K20I, M36I or K20I/M36I were designed. Their replication kinetics were analyzed by viral competition in the absence of PI. Susceptibility to six different PI was phenotypically assessed in clones and in recombinant viruses carrying non-B proteases from 16 drug-naive individuals.
  
  
  RESULTS
  In the absence of drug, the M36I clone replicated more rapidly than wt (wild type) or the double mutant K20I/M36I. Natural polymorphisms 20I and/or 36I improved the virus replicative capacity under drug pressure, reducing the susceptibility to saquinavir and indinavir, with IC(50) values 2-3.5-fold higher than wt. All but one drug-naive individual carrying non-B viruses were fully susceptibility to all tested PI, suggesting that additional substitutions within the PR might compensate the reduced PI susceptibility caused by K20I and/or M36I.
  
  
  CONCLUSIONS
  Natural PR polymorphisms in non-B HIV-1 variants can influence in vitro the virus replication capacity in the presence and/or absence or certain PI. Hypothetically, the improved viral replication of mutant 36I might favor a more rapid spreading of non-B subtypes of HIV-1.
authors.affiliation: Service of Infectious Diseases, Hospital Carlos III, Madrid, Spain. aholguin.hciii@salud.madrid.org
authors.forename: Africa
authors.initials: A
authors.lastname: Holguín
authors.forename: Carlos
authors.initials: C
authors.lastname: Suñe
authors.forename: François
authors.initials: F
authors.lastname: Hamy
authors.forename: Vincent
authors.initials: V
authors.lastname: Soriano
authors.forename: Thomas
authors.initials: T
authors.lastname: Klimkait
mesh_terms: D018920:Coculture Techniques; D014644:Genetic Variation; D016333:HIV Protease / Q000235:genetics*; D015497:HIV-1 / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D009154:Mutation; D011110:Polymorphism, Genetic; D011995:Recombination, Genetic; D019562:Viral Load; D014779:Virus Replication
chemical_list: D016333:HIV Protease