Functional and structural damage in Leishmania mexicana exposed to the cationic peptide dermaseptin

: The effect of dermaseptin (DS), a 34 amino acid residue cationic peptide isolated from Phyllomedusa sauvagii skin, has been studied on promastigotes of Leishmania mexicana growing in vitro. Within 5 min of incubation in the presence of DS, the flagellated parasites lost their motility. DS inhibited promastigote growth by 50% at a concentration of 3 microM and by 100% at 10 microM. Immunocytochemical, freeze fracture, label fracture and electron microscopic observations have shown that the amphipathic peptide generates perturbations of the lipid bilayer leading to altered permeability of the surface membrane and death of the parasite.