Characterization of human immunodeficiency virus type 1 variants with increased resistance to a C2-symmetric protease inhibitor

Abstract

Inhibitors of the human immunodeficiency virus type 1 protease represent a promising class of antiviral drugs for the treatment of AIDS, and several are now in clinical trials. Here, we report the in vitro selection of viral variants with decreased sensitivity to a C2-symmetric protease inhibitor (A-77003). We show that a single amino acid substitution (Arg to Gln or Lys) at position 8 of the protease results in a substantial decrease in the inhibitory activity of the drug on the enzyme and a comparable increase in viral resistance. These findings, when analyzed by using the three-dimensional structure of the protease-drug complex, provide a strategic guide for the future development of inhibitors of the human immunodeficiency virus type 1 protease.

Defining the level of human immunodeficiency virus type 1 (HIV-1) protease activity required for HIV-1 particle maturation and infectivity

“…This suggests that a reservoir of protease activity exists in an immature virion and that this reservoir can absorb a decrease in protease activity induced by point mutations in the enzyme. Point mutations in the protease which affect the binding of peptidomimetic inhibitors by 5-to 10-fold have been obtained by in vitro selection of viruses (5,12,26). It has been noted in at least one case that a virus containing an escape mutation in the protease is considerably less infectious than the parent virus (5) and that protease function is impaired.…”

“…It has been noted in at least one case that a virus containing an escape mutation in the protease is considerably less infectious than the parent virus (5) and that protease function is impaired. Although the presence of these mutations would aid in slowing the rate of viral spread, it is also clear that second-site mutations can occur to restore catalytic competence while maintaining resistance to inhibitors (12). Clearly, the development of effective protease inhibitors must now take into account the ability of the enzyme to survive in the presence of point mutations that may disrupt the binding of small-molecule inhibitors.…”

Incidence and impact of resistance against approved antiretroviral drugs

“…This was ®rst demonstrated by Ho et al, through the in vitro selection of HIV-1 resistant to a prototype PI, A-77003, with mutations R8Q and M46I. The position 8 mutation conferred reduced drug susceptibility, whereas the 46 mutation compensated for the loss of replicative ®tness consequent on the R8Q [96]. This early observation has allowed an appreciation of the multiple roles played by the array of PI resistance associated mutations which have now been documented.…”

Solvation effects are responsible for the reduced inhibitor affinity of some HIV‐1 PR mutants

“…Many of these compounds have been found to stop very effectively the replication of the HIV-1 virus in vitro (Wlodawer & Erickson, 1993). However, some of them seem to have limited clinical benefit, due in part to the development of drug resistance, which has been shown to exist in cell cultures (Otto et al, 1993;El-Farrash et al, 1994;Ho et al, 1994;Kaplan et al, 1994;Markowitz et al, 1995), and in clinical isolates from patients (Condra et al, 1995;Winslow et al, 1995). The HIV virus is able to generate drug resistance because of the high mutational frequency in the replication of its genome.…”

“…Moreover, some of the resistant mutant residues differ markedly from the original (native) ones in the size and shape of their side chains (e.g.. V82 + T, L63 -+ P) (Condra et al, 1995). Finally, several HIV-1 PR resistance strains have been found to contain multiple (two to four) mutations, which have been observed both in cell culture and in clinical isolates from patients (Ho et al, 1994;Condra et al, 1995).…”