K70Q adds high-level tenofovir resistance to "Q151M complex" HIV reverse transcriptase through the enhanced discrimination mechanism

PLoS One. 2011 Jan 13;6(1):e16242. doi: 10.1371/journal.pone.0016242.

Abstract

HIV-1 carrying the "Q151M complex" reverse transcriptase (RT) mutations (A62V/V75I/F77L/F116Y/Q151M, or Q151Mc) is resistant to many FDA-approved nucleoside RT inhibitors (NRTIs), but has been considered susceptible to tenofovir disoproxil fumarate (TFV-DF or TDF). We have isolated from a TFV-DF-treated HIV patient a Q151Mc-containing clinical isolate with high phenotypic resistance to TFV-DF. Analysis of the genotypic and phenotypic testing over the course of this patient's therapy lead us to hypothesize that TFV-DF resistance emerged upon appearance of the previously unreported K70Q mutation in the Q151Mc background. Virological analysis showed that HIV with only K70Q was not significantly resistant to TFV-DF. However, addition of K70Q to the Q151Mc background significantly enhanced resistance to several approved NRTIs, and also resulted in high-level (10-fold) resistance to TFV-DF. Biochemical experiments established that the increased resistance to tenofovir is not the result of enhanced excision, as K70Q/Q151Mc RT exhibited diminished, rather than enhanced ATP-based primer unblocking activity. Pre-steady state kinetic analysis of the recombinant enzymes demonstrated that addition of the K70Q mutation selectively decreases the binding of tenofovir-diphosphate (TFV-DP), resulting in reduced incorporation of TFV into the nascent DNA chain. Molecular dynamics simulations suggest that changes in the hydrogen bonding pattern in the polymerase active site of K70Q/Q151Mc RT may contribute to the observed changes in binding and incorporation of TFV-DP. The novel pattern of TFV-resistance may help adjust therapeutic strategies for NRTI-experienced patients with multi-drug resistant (MDR) mutations.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenine / analogs & derivatives*
  • Adenine / pharmacology
  • Catalytic Domain
  • Computer Simulation
  • Drug Resistance, Viral / genetics*
  • HIV / genetics
  • HIV / isolation & purification
  • HIV Reverse Transcriptase / genetics*
  • Humans
  • Hydrogen Bonding
  • Kinetics
  • Mutation, Missense*
  • Organophosphonates / pharmacology*
  • Reverse Transcriptase Inhibitors / pharmacology*
  • Tenofovir

Substances

  • Organophosphonates
  • Reverse Transcriptase Inhibitors
  • Tenofovir
  • HIV Reverse Transcriptase
  • Adenine