Interactions of Peptide Triazole Thiols with Env gp120 Induce Irreversible Breakdown and Inactivation of HIV-1 Virions

Background: We examined the underlying mechanism of action of the peptide triazole thiol, KR13 that has been shown previously to specifically bind gp120, block cell receptor site interactions and potently inhibit HIV-1 infectivity. Results: KR13, the sulfhydryl blocked KR13b and its parent non-sulfhydryl peptide triazole, HNG156, induced gp120 shedding but only KR13 induced p24 capsid protein release. The resulting virion post virolysis had an altered morphology, contained no gp120, but retained gp41 that bound to neutralizing gp41 antibodies. Remarkably, HIV-1 p24 release by KR13 was inhibited by enfuvirtide, which blocks formation of the gp41 6-helix bundle during membrane fusion, while no inhibition of p24 release occurred for enfuvirtide-resistant virus. KR13 thus appears to induce structural changes in gp41 normally associated with membrane fusion and cell entry. The HIV-1 p24 release induced by KR13 was observed in several clades of HIV-1 as well as in fully infectious HIV-1 virions. Conclusions: The antiviral activity of KR13 and its ability to inactivate virions prior to target cell engagement suggest that peptide triazole thiols could be highly effective in inhibiting HIV transmission across mucosal barriers and provide a novel probe to understand biochemical signals within envelope that are involved in membrane fusion

Fabrication of tailorable pH responsive cationic amphiphilic microgels on a microfluidic device for drug release

Cationic, amphiphilic microgels of differing compositions based on hydrophilic, pH, and thermoresponsive 2-(dimethylamino)ethyl methacrylate (DMAEMA) and hydrophobic, nonionic n-butyl acrylate (BuA) are synthesized using a lab-on-a-chip device. Hydrophobic oil-in-water (o/w) droplets are generated via a microfluidic platform, with the dispersed (droplet) phase containing the DMAEMA and BuA, alongside the hydrophobic cross-linker, ethylene glycol dimethacrylate, and a free radical initiator in an organic solvent. Finally, the hydrophobic droplets are photopolymerized via a UV light source as they traverse the microfluidic channel to produce the cationic amphiphilic microgels. This platform enables the rapid, automated, and in situ production of amphiphilic microgels, which do not match the core-shell structure of conventionally prepared microgels but are instead based on random amphiphilic copolymers of DMAEMA and BuA between the hydrophobic cross-links. The microgels are characterized in terms of their swelling and encapsulation abilities, which are found to be influenced by both the pH response and the hydrophobic content of the microgels. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 59–66

A Model of Peptide Triazole Entry Inhibitor Binding to HIV‑1 gp120 and the Mechanism of Bridging Sheet Disruption

Peptide triazole (PT) entry inhibitors prevent HIV-1 infection by blocking the binding of viral gp120 to both the HIV-1 receptor and the coreceptor on target cells. Here, we used all-atom explicit solvent molecular dynamics (MD) to propose a model for the encounter complex of the peptide triazoles with gp120. Saturation transfer difference nuclear magnetic resonance (STD NMR) and single-site mutagenesis experiments were performed to test the simulation results. We found that docking of the peptide to a conserved patch of residues lining the “F43 pocket” of gp120 in a bridging sheet naïve gp120 conformation of the glycoprotein led to a stable complex. This pose prevents formation of the bridging sheet minidomain, which is required for receptor–coreceptor binding, providing a mechanistic basis for dual-site antagonism of this class of inhibitors. Burial of the peptide triazole at the gp120 inner domain–outer domain interface significantly contributed to complex stability and rationalizes the significant contribution of hydrophobic triazole groups to peptide potency. Both the simulation model and STD NMR experiments suggest that the I-X-W [where X is (2<i>S</i>,4<i>S</i>)-4-(4-phenyl-1<i>H</i>-1,2,3-triazol-1-yl)­pyrrolidine] tripartite hydrophobic motif in the peptide is the major contributor of contacts at the gp120–PT interface. Because the model predicts that the peptide Trp side chain hydrogen bonding with gp120 S375 contributes to the stability of the PT–gp120 complex, we tested this prediction through analysis of peptide binding to gp120 mutant S375A. The results showed that a peptide triazole KR21 inhibits S375A with 20-fold less potency than WT, consistent with predictions of the model. Overall, the PT–gp120 model provides a starting point for both the rational design of higher-affinity peptide triazoles and the development of structure-minimized entry inhibitors that can trap gp120 into an inactive conformation and prevent infection