Revamil is a promising topical antimicrobial agent for prevention or treatment of infections, including those caused by multidrug-resistant bacteria.

Tissue surrounding biomedical devices forms a niche for bacteria. This is an as yet nonrecognized element in the pathogenesis of catheter-associated infections, with possible consequences for strategies of prevention and treatment of these infections.

Recent reports which show that several chemokines can act as direct microbicidal agents have drawn renewed attention to these chemotactic signalling proteins. Here we present a structure-function analysis of peptides derived from the human chemokines macrophage inflammatory protein-3alpha (MIP-3alpha/CCL20), interleukin-8 (IL-8), neutrophil activating protein-2 (NAP-2) and thrombocidin-1 (TC-1). These peptides encompass the C-terminal alpha-helices of these chemokines, which have been suggested to be important for the direct antimicrobial activities. Far-UV CD spectroscopy showed that the peptides are unstructured in aqueous solution and that a membrane mimetic solvent is required to induce a helical secondary structure. A co-solvent mixture was used to determine solution structures of the peptides by two-dimensional (1)H-NMR spectroscopy. The highly cationic peptide, MIP-3alpha(51-70), had the most pronounced antimicrobial activity and displayed an amphipathic structure. A shorter version of this peptide, MIP-3alpha(59-70), remained antimicrobial but its structure and mechanism of action were unlike that of the former peptide. The NAP-2 and TC-1 proteins differ in their sequences only by the deletion of two C-terminal residues in TC-1, but intact TC-1 is a very potent antimicrobial while NAP-2 is inactive. The corresponding C-terminal peptides, NAP-2(50-70) and TC-1(50-68), had very limited and no bactericidal activity, respectively. This suggests that other regions of TC-1 contribute to its bactericidal activity. Altogether, this work provides a rational structural basis for the biological activities of these peptides and proteins and highlights the importance of experimental characterization of peptide fragments as distinct entities because their activities and structural properties may differ substantially from their parent proteins.

Background:The properties required for antimicrobial activity of chemokines are unclear. Results: Native thrombocidin-1 requires a three-dimensional positive patch for activity, but unfolded thrombocidin-1 is active through the N-terminal linear peptide regions. Conclusion: Native thrombocidin-1 and unfolded thrombocidin-1 exert activity via distinct structural elements. Significance: Folded and unfolded antimicrobial chemokines can exert activity through different structural elements.