title: Nelfinavir-resistant, amprenavir-hypersusceptible strains of human immunodeficiency virus type 1 carrying an N88S mutation in protease have reduced infectivity, reduced replication capacity, and reduced fitness and process the Gag polyprotein precursor aberrantly.
abstract: The evolution of human immunodeficiency virus type 1 (HIV-1) strains with reduced susceptibility to protease inhibitors (PIs) is a major cause of PI treatment failure. A subset of subjects failing a therapy regimen containing the PI nelfinavir developed mutations at position 88 in the protease region. The N88S mutation occurring in some of these subjects induces amprenavir hypersusceptibility and a reduction of fitness and replication capacity. Here we demonstrate that substitutions L63P and V77I in protease, in combination, partially compensate for the loss of fitness, loss of replication capacity, loss of specific infectivity, and aberrant Gag processing induced by the N88S mutation. In addition, these mutations partially ablate amprenavir hypersusceptibility. Addition of mutation M46L to a strain harboring mutations L63P, V77I, and N88S resulted in a reduction of fitness and infectivity without changing Gag-processing efficiency, while amprenavir hypersusceptibility was further diminished. The ratio of reverse transcriptase activity to p24 protein was reduced in this strain compared to that in the other variants, suggesting that the M46L effect on fitness occurred through a mechanism different from a Gag-processing defect. We utilized these mutant strains to undertake a systematic comparison of indirect, single, cycle-based measures of fitness with direct, replication-based fitness assays and demonstrated that both yield consistent results. However, we observed that the magnitude of the fitness loss for one of the mutants varied depending on the assay used.
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Resch
authors.forename: Rainer
authors.initials: R
authors.lastname: Ziermann
authors.forename: Neil
authors.initials: N
authors.lastname: Parkin
authors.forename: Andrea
authors.initials: A
authors.lastname: Gamarnik
authors.forename: Ronald
authors.initials: R
authors.lastname: Swanstrom
mesh_terms: D002219:Carbamates; D002460:Cell Line; D018920:Coculture Techniques; D024882:Drug Resistance, Viral; D005663:Furans; D015683:Gene Products, gag / Q000378:metabolism; D015658:HIV Infections / Q000821:virology; D016333:HIV Protease / Q000235:genetics*; D017320:HIV Protease Inhibitors / Q000009:adverse effects / Q000494:pharmacology*; D015497:HIV-1 / Q000187:drug effects / Q000201:enzymology / Q000472:pathogenicity / Q000502:physiology*; D006801:Humans; D009154:Mutation; D019888:Nelfinavir / Q000494:pharmacology*; D011498:Protein Precursors / Q000378:metabolism; D013449:Sulfonamides / Q000009:adverse effects / Q000494:pharmacology*; D014779:Virus Replication
chemical_list: D002219:Carbamates; D005663:Furans; D015683:Gene Products, gag; D017320:HIV Protease Inhibitors; D011498:Protein Precursors; D013449:Sulfonamides; C095108:amprenavir; D016333:HIV Protease; D019888:Nelfinavir