Structural Modifications Alter Anti-HSV Activity of Tat-Derived Peptides

Abstract

Abstract: : Purpose: Peptides with membrane transiting ability block HSV infections in vitro and in vivo. The goal was to determine how various modifications of the tat peptide affect antiviral and microbicidal activity. Methods: Peptides were tested using a standard entry assay for antiviral activity and pre-incubation with virus, followed by serial dilution for microbicidal activity. Results: All peptides containing the intact transduction domain inhibited entry at low micromolar concentrations (2-10 µM) independent of any post-entry or cytotoxic effects. Some peptides also blocked entry indirectly by inactivating virions at concentrations between 5-25 µM. Inhibition by selective entry blockers with little or no effects on virions was largely or entirely reversible. Virus inactivation was not reversible over time or by high salt treatment or trypsinization of virions. Virus inactivation could be enhanced or inhibited depending on the C-terminal addition of a cysteine residue or other peptide extensions. Norleucine substitutions of charged residues interfered with both virus entry and virus inactivation. Inhibition of virus entry but not virus inactivation was rendered temperature-sensitive by substitutions of leucines at positions 50 and 51. Substitutions of arginines in positions 55 and 56 had varying effects depending on whether the peptides consisted of L- or D-isomers, even though no stereochemical effects were evident with the non-substituted peptides. Conclusions: We can alter the antiviral and microbicidal activity of tat-derived peptides by either adding extensions to the core or altering residues in the core tat peptide. The ability to modify the properties of these peptides increases their potential utility as antivirals and as tools to dissect the processes involved in viral entry.

Keywords: herpes simplex virus • antiviral drugs • keratitis