Activity of two synthetic amphiphilic peptides and magainin‐2 against herpes simplex virus types 1 and 2

The in vitro antiviral activity of two amphiphilic synthetic peptides, modelin‐1 (mod‐1) and modelin‐5 (mod‐5), and of the natural antibacterial peptide magainin‐2 (mag‐2) against herpes simplex viruses type 1 (HSV‐1) and 2 (HSV‐2) were evaluated. The peptides were incubated with the virus, i.e. direct inactivation, and their effects examined by means of plaque reduction assay and/or reduction in virus yield. Only mod‐ displayed a strong antiviral effect against HSV‐1 and HSV‐2, with 50% effective dose (ED₅₀) values of 4.6 and 4.1 μg/mL, respectively. Mag‐2, mod‐5 and a mixture of both had no significant inhibitory effect. Addition of mod‐1 up to a concentration of 100μg/mL to the culture medium had no significant cytotoxic effect on host vero cells, as measured by the trypan blue‐exclusion method. It showed, however, considerable hemolytic activity against human red blood cells. Experiments including acyclovir (ACV) as a reference viral inhibitor indicated that the mode of action of mod‐1 is different from that of ACV. In contrast to ACV, the peptide inactivates the virus following a very short incubation before vero cell infection, suggesting some kind of direct interaction of the peptide with the viral envelope, rather than inhibition of viral DNA replication or gene expression. Our results suggest that mod‐1 may be an effective topical antiviral agent against herpes viruses.