These two domains are connected by a 5-amino-acid linker. The CA protein consists of two domains, the N-terminal domain (NTD, aa 1-145) and the C-terminal domain (CTD, aa 151-231). The formation of this mature particle is essential for HIV-1 infectivity and the capsid protein (CA) obtained from the Gag cleavage product plays a central role in forming the conical virion core that surrounds the viral genome. In the immature form, Gag remains intact, whereas in the mature form, Gag is cleaved by the viral protease (PR). We cannot exclude the possibility that the CA-based peptides described here could elicit additional effects on virus replication not directly linked to their ability to bind CA-CTD.ĭuring HIV-1 assembly and morphogenesis, the structural protein, Gag, organizes into two completely different arrangements, immature and mature forms. The observation that relatively weak CA binders, such as NYAD-201 and NYAD-202, showed specificity and are able to disrupt the CTD dimer is encouraging for further exploration of a much broader class of antiviral compounds targeting CA. These preliminary data serve as the foundation for designing small, stable, α-helical peptides and small-molecule inhibitors targeted against the CTD dimer interface. These peptides also showed potent antiviral activity against a large panel of laboratory-adapted and primary isolates, including viral strains resistant to inhibitors of reverse transcriptase and protease. In in vitro assembly assays, the peptides inhibited mature-like virus particle formation and specifically inhibited HIV-1 production in cell-based assays. We also confirmed by using isothermal titration calorimetry (ITC), sedimentation equilibrium and NMR that these peptides indeed disrupt dimer formation. Therefore, we used the hydrocarbon stapling technique to stabilize the α-helical structure and confirmed by confocal microscopy that this modification also made these peptides cell-penetrating. However, these small peptides do not have any structure in solution and they do not penetrate cells. Resultsĭue to the pivotal role of the dimer interface, we reasoned that peptides from the α-helical region of the dimer interface might be effective as decoys to prevent CTD dimer formation. Therefore, the CTD represents a potential target for designing anti-HIV-1 drugs. Mutations of the residues at the CTD dimer interface impair virus assembly and render the virus non-infectious. The C-terminal domain (CTD) of HIV-1 capsid (CA), like full-length CA, forms dimers in solution and CTD dimerization is a major driving force in Gag assembly and maturation.
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