title: Long-term foscarnet therapy remodels thymidine analogue mutations and alters resistance to zidovudine and lamivudine in HIV-1.
abstract: OBJECTIVE
  To study the evolution of multi-drug-resistant HIV-1 in treatment-experienced patients receiving foscarnet (PFA) as part of salvage therapy and to investigate the virological consequences of emerging mutations.
  
  
  METHODS
  Genotypic and phenotypic resistance tests were performed on plasma viruses from seven patients at baseline and during treatment with PFA. The phenotypic effects of mutations suspected to be associated with PFA resistance were evaluated by site-directed mutagenesis of wild-type or thymidine analogue mutations (TAM)-carrying pNL4-3. Reversion of single mutations was performed in a patient-derived recombinant clone.
  
  
  RESULTS
  Baseline multi-drug-resistant isolates exhibited hypersusceptibility to PFA. In two patients who received > 12 months of PFA treatment, a novel mutation pattern including K70G, V75T, K219R and L228R emerged. These viruses had 3-6-fold resistance to PFA, a 2-20-fold decrease in resistance to zidovudine compared to baseline, and 14-39-fold resistance to lamivudine, in the absence of M184V. In wild-type clones mutations K70G and V75T induced moderate PFA resistance. In the case of TAMs, combinations of > or = 3 mutations (K70G+K219R+L228R+/-V75T) induced PFA resistance and decreased zidovudine resistance 3-13-fold. These mutants exhibited high-level lamivudine resistance (>20-fold) without mutation M184V. Reversion of K70G --> R and K219R --> E in a patient-derived clone confirmed the contribution of individual mutations and the negative association between PFA resistance and zidovudine resistance.
  
  
  CONCLUSIONS
  In the context of multiple TAMs, hypersusceptibility to PFA was observed and a novel pattern of resistance, including alternative amino acid substitutions at TAM loci, emerged. This mutational pattern was associated with decreases in zidovudine resistance and surprisingly high-level lamivudine resistance.
authors.affiliation: Department of Infectious Diseases, Rigshospitalet, University Hospital of Copenhagen, Denmark. sofiem@rh.dk
authors.forename: Sofie
authors.initials: S
authors.lastname: Mathiesen
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Dam
authors.forename: Birgit
authors.initials: B
authors.lastname: Roge
authors.forename: Louise Bruun
authors.initials: LB
authors.lastname: Joergensen
authors.forename: Alex Lund
authors.initials: AL
authors.lastname: Laursen
authors.forename: Jan
authors.initials: J
authors.lastname: Gerstoft
authors.forename: Francois
authors.initials: F
authors.lastname: Clavel
mesh_terms: D019943:Amino Acid Substitution; D019380:Anti-HIV Agents / Q000494:pharmacology*; D024921:Drug Resistance, Multiple, Viral / Q000235:genetics; D019143:Evolution, Molecular; D017245:Foscarnet / Q000494:pharmacology / Q000627:therapeutic use*; D015658:HIV Infections / Q000188:drug therapy* / Q000821:virology; D054303:HIV Reverse Transcriptase / Q000235:genetics; D015497:HIV-1 / Q000187:drug effects* / Q000235:genetics; D006801:Humans; D019259:Lamivudine / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D017354:Point Mutation; D018894:Reverse Transcriptase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D013045:Species Specificity; D013936:Thymidine / Q000031:analogs & derivatives / Q000235:genetics; D013997:Time Factors; D015215:Zidovudine / Q000494:pharmacology*
chemical_list: D019380:Anti-HIV Agents; D018894:Reverse Transcriptase Inhibitors; D019259:Lamivudine; D017245:Foscarnet; D015215:Zidovudine; D054303:HIV Reverse Transcriptase; D013936:Thymidine