Multi-step inhibition explains HIV-1 protease inhibitor pharmacodynamics and resistance
S. Alireza Rabi, … , Richard D. Moore, Robert F. Siliciano
S. Alireza Rabi, … , Richard D. Moore, Robert F. Siliciano
Published August 27, 2013
Citation Information: J Clin Invest. 2013;123(9):3848-3860. https://doi.org/10.1172/JCI67399.
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Multi-step inhibition explains HIV-1 protease inhibitor pharmacodynamics and resistance

Abstract

HIV-1 protease inhibitors (PIs) are among the most effective antiretroviral drugs. They are characterized by highly cooperative dose-response curves that are not explained by current pharmacodynamic theory. An unresolved problem affecting the clinical use of PIs is that patients who fail PI-containing regimens often have virus that lacks protease mutations, in apparent violation of fundamental evolutionary theory. Here, we show that these unresolved issues can be explained through analysis of the effects of PIs on distinct steps in the viral life cycle. We found that PIs do not affect virion release from infected cells but block entry, reverse transcription, and post–reverse transcription steps. The overall dose-response curves could be reconstructed by combining the curves for each step using the Bliss independence principle, showing that independent inhibition of multiple distinct steps in the life cycle generates the highly cooperative dose-response curves that make these drugs uniquely effective. Approximately half of the inhibitory potential of PIs is manifest at the entry step, likely reflecting interactions between the uncleaved Gag and the cytoplasmic tail (CT) of the Env protein. Sequence changes in the CT alone, which are ignored in current clinical tests for PI resistance, conferred PI resistance, providing an explanation for PI failure without resistance.

Authors

S. Alireza Rabi, Gregory M. Laird, Christine M. Durand, Sarah Laskey, Liang Shan, Justin R. Bailey, Stanley Chioma, Richard D. Moore, Robert F. Siliciano

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Figure 7

Effect of env mutations on PI resistance.

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Effect of env mutations on PI resistance. (A, D, and G) Mutations in E...
(A, D, and G) Mutations in Env can confer PI resistance. Pseudoviruses were generated with WT gag and pol genes and env genes E1 or E51 from a patient with high level PI resistance. Pseudoviruses were produced in the presence of various concentrations of the indicated PIs and used to infect CD4+ lymphoblasts. Three days later, the infection was quantified as the percentage of cells expressing GFP. Control WT infections were done with pseudoviruses carrying NL4-3 env. (B, E, and H) Envs from patients who failed PI-containing regimens without evidence of major PI mutations confer PI resistance. Pseudoviruses were generated with WT gag and pol genes and env genes cloned from patients PIE1 and PIE2 and analyzed as described above. (C, F, and I) Effect of mutations in the gp41 CT on PI sensitivity. Pseudoviruses generated with WT gag and pol and a chimeric NL4-3 env with the CT from PIE2 (NL4-3-PIE2-CT) were analyzed as above. Dose-response curves for ATV, DRV, and LPV are shown. Drug concentrations are normalized to the IC50 values for infectivity measured in (2) and are 13.6 nM, 23.6 nM, and 35.8 nM for ATV, DRV, and LPV, respectively.