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Dual-acting stapled peptides target both HIV-1 entry and assembly

Hongtao Zhang1, Francesca Curreli1, Abdul A Waheed2, Peter Y Mercredi3, Mansi Mehta3, Pallavi Bhargava3, Daniel Scacalossi1, Xiaohe Tong4, Shawn Lee4, Alan Cooper5, Michael F Summers3, Eric O Freed2 and Asim K Debnath1*

Author Affiliations

1 Laboratory of Molecular Modeling, Drug Design, Lindsley F. Kimball Research Institute of the New York Blood Center, 310 E 67th Street, New York, NY 10065, USA

2 Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute-Frederick, Frederick, MD 21702, USA

3 Howard Hughes Medical Institute and Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA

4 CPC Scientific, Inc., 1245 Reamwood Ave., Sunnyvale, CA 94089, USA

5 School of Chemistry, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK

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Retrovirology 2013, 10:136  doi:10.1186/1742-4690-10-136

Published: 15 November 2013

Abstract

Background

Previously, we reported the conversion of the 12-mer linear and cell-impermeable peptide CAI to a cell-penetrating peptide NYAD-1 by using an i,i + 4 hydrocarbon stapling technique and confirmed its binding to the C-terminal domain (CTD) of the HIV-1 capsid (CA) protein with an improved affinity (Kd ~ 1 μM) compared to CAI (Kd ~ 15 μM). NYAD-1 disrupts the formation of both immature- and mature-like virus particles in in vitro and cell-based assembly assays. In addition, it displays potent anti-HIV-1 activity in cell culture against a range of laboratory-adapted and primary HIV-1 isolates.

Results

In this report, we expanded the study to i,i + 7 hydrocarbon-stapled peptides to delineate their mechanism of action and antiviral activity. We identified three potent inhibitors, NYAD-36, -66 and -67, which showed strong binding to CA in NMR and isothermal titration calorimetry (ITC) studies and disrupted the formation of mature-like particles. They showed typical α-helical structures and penetrated cells; however, the cell penetration was not as efficient as observed with the i,i + 4 peptides. Unlike NYAD-1, the i,i + 7 peptides did not have any effect on virus release; however, they impaired Gag precursor processing. HIV-1 particles produced in the presence of these peptides displayed impaired infectivity. Consistent with an effect on virus entry, selection for viral resistance led to the emergence of two mutations in the gp120 subunit of the viral envelope (Env) glycoprotein, V120Q and A327P, located in the conserved region 1 (C1) and the base of the V3 loop, respectively.

Conclusion

The i,i + 7 stapled peptides derived from CAI unexpectedly target both CA and the V3 loop of gp120. This dual-targeted activity is dependent on their ability to penetrate cells as well as their net charge. This mechanistic revelation will be useful in further modifying these peptides as potent anti-HIV-1 agents.

Keywords:
HIV-1; Capsid; Virus assembly; Virus entry; Stapled peptides; NMR; SPR; ITC; Drug-resistance