title: Selection of drug-resistant feline immunodeficiency virus (FIV) encoding FIV/HIV chimeric protease in the presence of HIV-specific protease inhibitors.
abstract: An infectious chimeric feline immunodeficiency virus (FIV)/HIV strain carrying six HIV-like protease (PR) mutations (I37V/N55M/V59I/I98S/Q99V/P100N) was subjected to selection in culture against the PR inhibitor lopinavir (LPV), darunavir (DRV), or TL-3. LPV selection resulted in the sequential emergence of V99A (strain S-1X), I59V (strain S-2X), and I108V (strain S-3X) mutations, followed by V37I (strain S-4X). Mutant PRs were analyzed in vitro, and an isogenic virus producing each mutant PR was analyzed in culture for LPV sensitivity, yielding results consistent with the original selection. The 50% inhibitory concentrations (IC50s) for S-1X, S-2X, S-3X, and S-4X were 95, 643, 627, and 1,543 nM, respectively. The primary resistance mutations, V99(82)A, I59(50)V, and V37(32)I, are consistent with the resistance pattern developed by HIV-1 under similar selection conditions. While resistance to LPV emerged readily, similar PR mutations causing resistance to either DRV or TL-3 failed to emerge after passage for more than a year. However, a G37D mutation in the nucleocapsid (NC) was observed in both selections and an isogenic G37D mutant replicated in the presence of 100 nM DRV or TL-3, whereas parental chimeric FIV could not. An additional mutation, L92V, near the PR active site in the folded structure recently emerged during TL-3 selection. The L92V mutant PR exhibited an IC50 of 50 nM, compared to 35 nM for 6s-98S PR, and processed the NC-p2 junction more efficiently, consistent with increased viral fitness. These findings emphasize the role of mutations outside the active site of PR in increasing viral resistance to active-site inhibitors and suggest additional targets for inhibitor development.
authors.affiliation: Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, USA.
authors.forename: Ying-Chuan
authors.initials: YC
authors.lastname: Lin
authors.forename: Meaghan
authors.initials: M
authors.lastname: Happer
authors.forename: John H
authors.initials: JH
authors.lastname: Elder
mesh_terms: D004252:DNA Mutational Analysis; D024882:Drug Resistance, Viral; D016333:HIV Protease / Q000235:genetics / Q000378:metabolism*; D017320:HIV Protease Inhibitors / Q000494:pharmacology*; D015497:HIV-1 / Q000201:enzymology* / Q000235:genetics; D016089:Immunodeficiency Virus, Feline / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification; D020128:Inhibitory Concentration 50; D008826:Microbial Sensitivity Tests; D020125:Mutation, Missense; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012641:Selection, Genetic; D012692:Serial Passage
chemical_list: D017320:HIV Protease Inhibitors; D011993:Recombinant Fusion Proteins; D016333:HIV Protease