title: Identification of a novel resistance (E40F) and compensatory (K43E) substitution in HIV-1 reverse transcriptase.
abstract: BACKGROUND
  HIV-1 nucleoside reverse transcriptase inhibitors (NRTIs) have been used in the clinic for over twenty years. Interestingly, the complete resistance pattern to this class has not been fully elucidated. Novel mutations in RT appearing during treatment failure are still being identified. To unravel the role of two of these newly identified changes, E40F and K43E, we investigated their effect on viral drug susceptibility and replicative capacity.
  
  
  RESULTS
  A large database (Quest Diagnostics database) was analysed to determine the associations of the E40F and K43E changes with known resistance mutations. Both amino acid changes are strongly associated with the well known NRTI-resistance mutations M41L, L210W and T215Y. In addition, a strong positive association between these changes themselves was observed. A panel of recombinant viruses was generated by site-directed mutagenesis and phenotypically analysed. To determine the effect on replication capacity, competition and in vitro evolution experiments were performed. Introduction of E40F results in an increase in Zidovudine resistance ranging from nine to fourteen fold depending on the RT background and at the same time confers a decrease in viral replication capacity. The K43E change does not decrease the susceptibility to Zidovudine but increases viral replication capacity, when combined with E40F, demonstrating a compensatory role for this codon change.
  
  
  CONCLUSIONS
  In conclusion, we have identified a novel resistance (E40F) and compensatory (K43E) change in HIV-1 RT. Further research is indicated to analyse the clinical importance of these changes.
authors.affiliation: Department of Medical Microbiology, University Medical Center Utrecht, The Netherlands. c.d.g.huigen@umcutrecht.nl
authors.forename: Marleen C D G
authors.initials: MC
authors.lastname: Huigen
authors.forename: Petronella M
authors.initials: PM
authors.lastname: van Ham
authors.forename: Loek
authors.initials: L
authors.lastname: de Graaf
authors.forename: Ron M
authors.initials: RM
authors.lastname: Kagan
authors.forename: Charles A B
authors.initials: CA
authors.lastname: Boucher
authors.forename: Monique
authors.initials: M
authors.lastname: Nijhuis
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D002460:Cell Line; D003588:Cytopathogenic Effect, Viral; D019020:Directed Molecular Evolution; D024882:Drug Resistance, Viral; D054303:HIV Reverse Transcriptase / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000187:drug effects / Q000235:genetics / Q000254:growth & development*; D006801:Humans; D020128:Inhibitory Concentration 50; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D018894:Reverse Transcriptase Inhibitors / Q000494:pharmacology*; D014779:Virus Replication / Q000187:drug effects; D015215:Zidovudine / Q000494:pharmacology*
chemical_list: D018894:Reverse Transcriptase Inhibitors; D015215:Zidovudine; C514824:reverse transcriptase, Human immunodeficiency virus 1; D054303:HIV Reverse Transcriptase