Negatively Charged Glyconanoparticles Modulate and Stabilize the Secondary Structures of a gp120 V3 Loop Peptide: Toward Fully Synthetic HIV Vaccine Candidates

The third variable region (V3 peptide) of the HIV-1 gp120 is a major immunogenic domain of HIV-1. Controlling the formation of the immunologically active conformation is a crucial step to the rational design of fully synthetic candidate vaccines. Herein, we present the modulation and stabilization of either the α-helix or β-strand conformation of the V3 peptide by conjugation to negatively charged gold glyconanoparticles (GNPs). The formation of the secondary structure can be triggered by the variation of the buffer concentration and/or pH as indicated by circular dichoism. The peptide on the GNPs shows increased stability toward peptidase degradation as compared to the free peptide. Moreover, only the V3β-GNPs bind to the anti-V3 human broadly neutralizing mAb 447-52D as demonstrated by surface plasmon resonance (SPR). The strong binding of V3β-GNPs to the 447-52D mAb was the starting point to address its study as immunogen. V3β-GNPs elicit antibodies in rabbits that recognize a recombinant gp120 and the serum displayed low but consistent neutralizing activity. These results open up the way for the design of new fully synthetic HIV vaccine candidates

Isolation, Structural Modification, and HIV Inhibition of Pentacyclic Lupane-Type Triterpenoids from <i>Cassine xylocarpa</i> and <i>Maytenus cuzcoina</i>

As a part of our investigation into new anti-HIV agents, we report herein the isolation, structure elucidation, and biological activity of six new (<b>1</b>–<b>6</b>) and 20 known (<b>7</b>–<b>26</b>) pentacyclic lupane-type triterpenoids from the stem of <i>Cassine xylocarpa</i> and root bark of <i>Maytenus cuzcoina</i>. Their stereostructures were elucidated on the basis of spectroscopic and spectrometric methods, including 1D and 2D NMR techniques. To gain a more complete understanding of the structural requirements for anti-HIV activity, derivatives <b>27</b>–<b>48</b> were prepared by chemical modification of the main secondary metabolites. Sixteen compounds from this series displayed inhibitory effects of human immunodeficiency virus type 1 replication with IC₅₀ values in the micromolar range, highlighting compounds <b>12</b>, <b>38</b>, and <b>42</b> (IC₅₀ 4.08, 4.18, and 1.70 μM, respectively) as the most promising anti-HIV agents