title: Differential impact of the HIV-1 non-nucleoside reverse transcriptase inhibitor mutations K103N and M230L on viral replication and enzyme function.
abstract: OBJECTIVE
  We wished to study the resistance profile of etravirine, a novel non-nucleoside reverse transcriptase inhibitor (NNRTI) active against common human immunodeficiency virus type-1 (HIV-1) drug-resistant strains.
  
  
  METHODS
  We compared the effects of K103N, the most prevalent NNRTI resistance mutation, and M230L on enzyme function, virus replication and extent of biochemical inhibition by etravirine, efavirenz and nevirapine.
  
  
  RESULTS
  Growth kinetics analyses in cord blood mononuclear cells (CBMCs) demonstrated that K103N-containing virus replicated as well as wild-type (WT) virus and that the M230L-containing virus was severely impaired in replication ability in the absence of NNRTIs. K103N-containing viruses replicated well in the presence of efavirenz and nevirapine, while virus containing M230L displayed substantial replication in the presence of all NNRTIs tested. RNA-dependent DNA polymerase assays using a heterogeneous HIV-1 RNA template and purified recombinant WT or mutated reverse transcriptase enzymes revealed that the fold change (FC) for etravirine was 0.7 for K103N and 8 for M230L. K103N and M230L conferred high-level resistance to both efavirenz (FC=39 and 15.3, respectively) and nevirapine (FC=43.5 and 33), confirming that M230L confers cross-resistance to both drugs while K103N-containing viruses remain susceptible to etravirine. In enzymatic assays, the K103N mutation was associated with moderate reductions in the efficiency of 3' DNA end-directed RNA template cleavage, while comparable efficiency to WT enzyme was observed with regard to minus-strand strong stop DNA synthesis and polymerase processivity.
  
  
  CONCLUSIONS
  These properties help to explain differences in the evolution and prevalence of these two NNRTI mutations.
authors.affiliation: McGill University AIDS Centre, Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada.
authors.forename: Hong-Tao
authors.initials: HT
authors.lastname: Xu
authors.forename: Maureen
authors.initials: M
authors.lastname: Oliveira
authors.forename: Yudong
authors.initials: Y
authors.lastname: Quan
authors.forename: Tamara
authors.initials: T
authors.lastname: Bar-Magen
authors.forename: Mark A
authors.initials: MA
authors.lastname: Wainberg
mesh_terms: D000480:Alkynes; D019943:Amino Acid Substitution / Q000235:genetics; D019380:Anti-HIV Agents / Q000494:pharmacology; D048588:Benzoxazines / Q000494:pharmacology; D003521:Cyclopropanes; D024882:Drug Resistance, Viral; D054303:HIV Reverse Transcriptase / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D020125:Mutation, Missense; D019829:Nevirapine / Q000494:pharmacology; D009570:Nitriles; D011724:Pyridazines / Q000494:pharmacology; D011743:Pyrimidines; D018894:Reverse Transcriptase Inhibitors / Q000494:pharmacology*; D014779:Virus Replication
chemical_list: D000480:Alkynes; D019380:Anti-HIV Agents; D048588:Benzoxazines; D003521:Cyclopropanes; D009570:Nitriles; D011724:Pyridazines; D011743:Pyrimidines; D018894:Reverse Transcriptase Inhibitors; C451734:etravirine; D019829:Nevirapine; C514824:reverse transcriptase, Human immunodeficiency virus 1; D054303:HIV Reverse Transcriptase; C098320:efavirenz