Inhibition of Herpes Simplex Virus Type 1 and Type 2 Infections by Peptide-Derivatized Dendrimers

Abstract

In response to the need for new antiviral agents, dendrimer-based molecules have been recognized as having a large number of potential therapeutic applications. They include peptide-derivatized dendrimers, which are hyperbranched synthetic well-defined molecules which consist of a peptidyl branching core and covalently attached surface functional peptides. However, few studies have addressed their applications as direct-acting antiviral agents. Here, we report on the ability of the peptide dendrimer SB105 and its derivative, SB105_A10, to directly inhibit herpes simplex virus 1 (HSV-1) and HSV-2 in vitro replication, with favorable selective indexes discerned for both compounds. An analysis of their mode of action revealed that SB105 and SB105_A10 prevent HSV-1 and HSV-2 attachment to target cells, whereas SB104, a dendrimer with a different amino acid sequence within the functional group and minimal antiviral activity, was ineffective in blocking HSV attachment. Moreover, both SB105 and SB105_A10 retained their ability to inhibit HSV adsorption at pH 3.0 and 4.0 and in the presence of 10% human serum proteins, conditions mimicking the physiological properties of the vagina, a potential therapeutic location for such compounds. The inhibition of HSV adsorption is likely to stem from the ability of SB105_A10 to bind to the glycosaminoglycan moiety of cell surface heparan sulfate proteoglycans, thereby blocking virion attachment to target cells. Finally, when combined with acyclovir in checkerboard experiments SB105_A10 exhibited highly synergistic activity. Taken together, these findings suggest that SB105 and SB105_A10 are promising candidates for the development of novel topical microbicides for the prevention of HSV infections.

Folded Structure and Insertion Depth of the Frog-Skin Antimicrobial Peptide Esculentin-1b(1–18) in the Presence of Differently Charged Membrane-Mimicking Micelles

“…They are part of the innate immune system of the majority of the multicellular organisms, and are typically characterized by a wide spectrum of antimicrobial activity, from Gram-negative to Gram-positive bacteria, fungi, protozoa and enveloped viruses. [5][6][7] Despite amino acid sequence homology is not high, AMPs share some common features. They are relatively short (< 60 residues), cationic, have a large content (≥ 50%) of hydrophobic residues and adopt an amphipathic three-dimensional folding when interacting with pathogens" membranes.…”

“…They are relatively short (< 60 residues), cationic, have a large content (≥ 50%) of hydrophobic residues and adopt an amphipathic three-dimensional folding when interacting with pathogens" membranes. 6 Generally, AMPs destroy or permeate the microbial plasma-membrane. The membrane is formed through evolutionarily well conserved biosynthetic processes and represents a non-selective target, making modifications by the microorganisms difficult and, thus, resistance onset is unlikely.…”

“…Also the net positive charge plays a fundamental role. The content of negatively charged lipids is generally higher for microbial than eukaryotic cell membranes, 6,12,13 thus, AMPs are electrostatically attracted by the former to a greater extent, on the one hand, and cytotoxicity is kept relatively low on the other. In this scenario, the characterization of the 3D structure of AMPs when interacting with suitable membrane mimicking models is absolutely needed to deeply investigate peptide-membrane interactions at a molecular level and to provide fundamental information about the mechanism underlying the antimicrobial activity.…”

“…23 A globally amphipathic structure was found, with a helical conformation for the N-terminal portion (encompassing the first 12 residues) and an unfolded C-terminal fragment. 23 However, as the H 2 O/TFE solvent is an isotropic environment, such a structural model for Esc (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) should be taken with caution. Despite promoting peptide folding by favoring intramolecular H-bonds, indeed, H 2 O/TFE mixtures inherently lack the intrinsic anisotropic character of a lipid bilayer.…”

“…In particular, both zwitterionic and negatively charged micelles have been employed to model eukaryotic and prokaryotic plasma membrane, respectively, as bacterial membranes are usually characterized by a higher content of negatively charged lipids than the former. 6,12,13 The insertion depth of Esc (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) into the micelles was estimated by using Mn 2+ ions as a paramagnetic probe. The results clearly confirm the helical folding of Esc (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) and show how binding and folding are prominent only in the presence of a negatively charged membrane.…”