The study found that LL‑37, a common human antimicrobial peptide, barely stopped herpes simplex virus (HSV‑1 or HSV‑2) from infecting cells, so it isn’t useful as an anti‑herpes supplement. Some other natural peptides did work, but many are toxic or need more research.

A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide microplate assay was adapted to screen for the ability of 20 host-defense peptides to inactivate herpes simplex virus type 1 and type 2. The procedure required minimal amounts of material, was reproducible, and was confirmed with standard antiviral testing techniques. In screening tests, with the exception of melittin, a highly cytotoxic and hemolytic peptide found in bee venom, the alpha-helical peptides in our test panel (magainins, cecropins, clavanins, and LL-37) caused little viral inactivation. Several beta-sheet peptides (defensins, tachyplesin, and protegrins) inactivated one or both viruses, sometimes with remarkable selectivity. Two peptides were identified as having antiviral activity against both viruses, indolicidin (a tryptophan-rich peptide from bovine neutrophils) and brevinin-1 (a peptide found in frog skin). The antiviral activity of these two peptides was confirmed with standard antiviral assays. Interestingly, the antiviral activity of brevinin-1 was maintained after reduction and carboxamidomethylation, procedures that abolished its otherwise prominent hemolytic and cytotoxic effects.