Peptide Triazole Thiol Irreversibly Inactivates Metastable HIV-1 Env by Accessing Conformational Triggers Intrinsic to Virus–Cell Entry

Abstract

KR13, a peptide triazole thiol previously established to inhibit HIV-1 infection and cause virus lysis, was evaluated by flow cytometry against JRFL Env-presenting cells to characterize induced Env and membrane transformations leading to irreversible inactivation. Transiently transfected HEK293T cells were preloaded with calcein dye, treated with KR13 or its thiol-blocked analogue KR13b, fixed, and stained for gp120 (35O22), MPER (10E8), 6-helix-bundle (NC-1), immunodominant loop (50-69), and fusion peptide (VRC34.01). KR13 induced dose-dependent transformations of Env and membrane characterized by transient poration, MPER exposure, and 6-helix-bundle formation (analogous to native fusion events), but also reduced immunodominant loop and fusion peptide exposure. Using a fusion peptide mutant (V504E), we found that KR13 transformation does not require functional fusion peptide for poration. In contrast, simultaneous treatment with fusion inhibitor T20 alongside KR13 prevented membrane poration and MPER exposure, showing that these events require 6-helix-bundle formation. Based on these results, we formulated a model for PTT-induced Env transformation portraying how, in the absence of CD4/co-receptor signaling, PTT may provide alternate means of perturbing the metastable Env-membrane complex, and inducing fusion-like transformation. In turn, the results show that such transformations are intrinsic to Env and can be diverted for irreversible inactivation of the protein complex.

Irreversible Inactivation of SARS-CoV-2 by Lectin Engagement with Two Glycan Clusters on the Spike Protein

“…Detected leakage was limited and dose-dependent (Supplemental Figure S4). Of note, in previous studies, where HIV-1 lysis was observed, p24 release occurred as an apparent result of disturbing the metastable structure of the HIV-1 Env spike, and causing conformational rearrangement and irreversible inactivation of spike before target cell encounter. − We, therefore, explored this latter possibility for SARS-CoV-2 by examining the viruses after stringent washouts following lectin exposure, before target cell infection. Indeed, we observed that CV-N-treatment irreversibly inactivates SARS-CoV-2 pseudovirus, with an IC 50 of 242.2 ± 191.6 nM (Figure A).…”

Irreversible Inactivation of SARS-CoV-2 by Lectin Engagement with Two Glycan Clusters on the Spike Protein

“…Detected leakage was limited and dose-dependent (Supplemental Figure S4). Of note, in previous studies where HIV-1 lysis was observed, p24 release occurred as an apparent result of disturbing the metastable structure of the HIV-1 Env spike, and causing conformational rearrangement and irreversible inactivation of spike before target cell encounter (18)(19)(20). We therefore explored this latter possibility for SARS-CoV-2 by examining the viruses after stringent washouts following lectin exposure, before target cell infection.…”

Pharmacophore Variants of the Macrocyclic Peptide Triazole Inactivator of HIV-1 Env

“…Macrocyclic peptide triazoles (cPTs) have been devised with molecular weights of less than 1000 Da (comparable to small molecules), protease resistance, and greatly increased serum half-life [12,13]. Furthermore, thiol functionalization of linear and cyclic PTs affords a subclass of variant PTs that cause further inactivation effects by virus membrane poration [14][15][16][17].…”