Impact of novel human immunodeficiency virus type 1 reverse transcriptase mutations P119S and T165A on 4'-ethynylthymidine analog resistance profile

Antimicrob Agents Chemother. 2009 Nov;53(11):4640-6. doi: 10.1128/AAC.00686-09. Epub 2009 Aug 24.


2',3'-Didehydro-3'-deoxy-4'-ethynylthymidine (4'-Ed4T), a derivative of stavudine (d4T), has potent activity against human immunodeficiency virus and is much less inhibitory to mitochondrial DNA synthesis and cell growth than its progenitor, d4T. 4'-Ed4T triphosphate was a better reverse transcriptase (RT) inhibitor than d4T triphosphate, due to the additional binding of the 4'-ethynyl group at a presumed hydrophobic pocket in the RT active site. Previous in vitro selection for 4'-Ed4T-resistant viral strains revealed M184V and P119S/T165A/M184V mutations on days 26 and 81, respectively; M184V and P119S/T165A/M184V conferred 3- and 130-fold resistance to 4'-Ed4T, respectively. We investigated the relative contributions of these mutations, engineered into the strain NL4-3 background, to drug resistance, RT activity, and viral growth. Viral variants with single RT mutations (P119S or T165A) did not show resistance to 4'-Ed4T; however, M184V and P119S/T165A/M184V conferred three- and fivefold resistance, respectively, compared with that of the wild-type virus. The P119S/M184V and T165A/M184V variants showed about fourfold resistance to 4'-Ed4T. The differences in the growth kinetics of the variants were not more than threefold. The purified RT of mutants with the P119S/M184V and T165A/M184V mutations were inhibited by 4'-Ed4TTP with 8- to 13-fold less efficiency than wild-type RT. M184V may be the primary resistance-associated mutation of 4'-Ed4T, and P119S and T165A are secondary mutations. On the basis of our findings and the results of structural modeling, a virus with a high degree of resistance to 4'-Ed4T (e.g., more than 50-fold resistance) will be difficult to develop. The previously observed 130-fold resistance of the virus with P119S/T165A/M184V to 4'-Ed4T may be partly due to mutations both in the RT sequence and outside the RT sequence.

Publication types

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

MeSH terms

  • Anti-HIV Agents / pharmacology*
  • Computer Simulation
  • Drug Resistance, Viral
  • HIV Reverse Transcriptase / genetics*
  • HIV-1 / drug effects*
  • Humans
  • Microbial Sensitivity Tests
  • Mutation*
  • Reverse Transcriptase Inhibitors / pharmacology
  • Stavudine / analogs & derivatives*
  • Stavudine / pharmacology


  • Anti-HIV Agents
  • Reverse Transcriptase Inhibitors
  • 2',3'-didehydro-3'-deoxy-4'-ethynylthymidine
  • Stavudine
  • reverse transcriptase, Human immunodeficiency virus 1
  • HIV Reverse Transcriptase