title: Natural resistance-associated mutations to Enfuvirtide (T20) and polymorphisms in the gp41 region of different HIV-1 genetic forms from T20 naive patients.
abstract: BACKGROUND
  The natural occurrence of primary resistance mutations in reverse transcriptase (RT) and protease (PR) genes of HIV-1 isolates from untreated patients has been reported and it may have important implications for the response to drug treatment. It is predictable that the same occurs in the HR1 region of gp41 sequence from patients who have never received T20 therapy, and in this regard it would be important to know not only the mutation frequencies at HR1 region but also the natural polymorphisms at resistance-associated positions present in the absence of this drug.
  
  
  OBJECTIVE
  The objectives of this study are to investigate the existence of natural resistance-associated mutations to T20 in HR1 gp41 region corresponding to different HIV-1 genetic forms from T20 naive patients and to determine their prevalence.
  
  
  METHODS
  Two hundred HIV-1 gp41 sequences were included: subtype B: 164 (81.3%); subtype A: 15 (8.2%); subtype G: 10 (4.6%); subtype F: 6 (3.5%); subtype C: 3 (1.8%); subtype K: 1 (0.6%); and subtype D: 1 (0.6%). We analyzed the resistance-associated mutations previously described: Q32H/R, G36D/S, I37V, V38A/M, Q39R/H, Q40H, N42T/D/Q/H, N43D/S/K/Q, L44M, L45M, R46M and V69I.
  
  
  RESULTS
  Natural resistance mutations to T20 were found at a high frequency: 10.5%, corresponding to 9.1% in subtype B and 16.7% in non-B subtype samples. Polymorphisms were more frequent in non-B and recombinant forms than in subtype B (p<0.001). Different substitutions were related to subtypes: N42S in subtypes A, B, G and C, but not in F, Q56R in subtype A from CRF02_AG, and L54M in subtype B from CRF14_BG.
  
  
  CONCLUSIONS
  To our knowledge this is the first study describing natural-resistance to T20 among different HIV-1 subtypes, warranting a study of the biological significance of this mutations and their clinical relevance. The detection of differences between subtypes may have an influence on the rate and patterns of resistance in patients undergoing T20 treatment.
authors.affiliation: Area de Patogenia Viral, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, 28220 Madrid, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Carmona
authors.forename: L
authors.initials: L
authors.lastname: Pérez-Alvarez
authors.forename: M
authors.initials: M
authors.lastname: Muñoz
authors.forename: G
authors.initials: G
authors.lastname: Casado
authors.forename: E
authors.initials: E
authors.lastname: Delgado
authors.forename: M
authors.initials: M
authors.lastname: Sierra
authors.forename: M
authors.initials: M
authors.lastname: Thomson
authors.forename: Y
authors.initials: Y
authors.lastname: Vega
authors.forename: E
authors.initials: E
authors.lastname: Vázquez de Parga
authors.forename: G
authors.initials: G
authors.lastname: Contreras
authors.forename: L
authors.initials: L
authors.lastname: Medrano
authors.forename: R
authors.initials: R
authors.lastname: Nájera
mesh_terms: D000595:Amino Acid Sequence; D019380:Anti-HIV Agents / Q000627:therapeutic use*; D018076:DNA, Complementary / Q000737:chemistry / Q000302:isolation & purification; D004279:DNA, Viral / Q000737:chemistry / Q000302:isolation & purification; D024882:Drug Resistance, Viral / Q000235:genetics; D000077560:Enfuvirtide; D005787:Gene Frequency; D015700:HIV Envelope Protein gp41 / Q000235:genetics* / Q000627:therapeutic use; D015658:HIV Infections / Q000821:virology*; D015497:HIV-1 / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D010446:Peptide Fragments / Q000627:therapeutic use*; D011110:Polymorphism, Genetic; D012367:RNA, Viral; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013030:Spain
chemical_list: D019380:Anti-HIV Agents; D018076:DNA, Complementary; D004279:DNA, Viral; D015700:HIV Envelope Protein gp41; D010446:Peptide Fragments; D012367:RNA, Viral; D000077560:Enfuvirtide