Antimicrobial Peptides – Molecules With Multiple Biological Functions

Antimicrobial peptides (AMPs), also called host defense peptides, represent a ubiquitous response in nature to overcome microbial infections or in competing for an ecological niche. They are produced by species belonging to all kingdoms of life, frequently found in bacteria, fungi, plants, insects, amphibians, crustaceans, fish and mammals. These peptides have emerged as central components of the innate defenses of both lower and higher organisms. There are more than 2000 naturally described peptides, the vast majority are cationic. In humans so far over one hundred antimicrobial peptides have been discovered. Although they have an enormous variety of sequences and structures, they share certain common features. Cationic antimicrobial peptides are 5-80 amino acids in length with at least one excess positive charge due to lysine and arginine residues and contain hydrophobic amino acids. They are structurally diverse, comprising linear, α-helical, β-sheets, loops and combined structures often stabilized by disulfide bridges. AMPs have received more attention with the growing threat of antimicrobial resistance. Of particular interest is their ability to kill multi-drug resistant bacteria. Antimicrobial peptides (AMPs) are potential novel antimicrobial drugs with some much-desired features, including a low chance of developing drug resistance, fast acting, broad-spectrum activity and active against multi-drug resistant bacteria. However, despite their beneficial antimicrobial activity, some antimicrobial peptides can also harm the host cells. So far only a few have been investigated in clinical studies. Within the last two decades it has become increasingly clear that antimicrobial peptides play a major role in regulating the process of innate immunity. Some AMPs can have direct and indirect chemotactic functions. Human defensins, for example, play a major role in recruiting monocytes and mast cells towards inflammatory sites. AMPs also can regulate the inflammatory response by interacting with TLR receptors. In this function AMPs can protect the host or support the clearance from infections. In addition, some AMPs have direct and indirect activity on wound healing.
In this Research Topic we focus on the multiple biological functions of these peptides and want to collect a bouquet of different manuscripts describing such functions. This includes antibacterial activity for planktonic cells as well as for biofilms. In the last years, reports show that AMPs can inhibit biofilm formation as well as destroy established biofilm, often at a concentration below the minimal inhibitory concentration (MIC) for planktonic cells, quite opposite from conventional antibiotics. We are also interested in AMPs bound to the surface that can protect surfaces from bacterial settlement and biofilm formation. Furthermore, AMPs can kill viruses, fungi, and parasites. Many AMPs can influence the immune system in many different ways and therefore can be supporting the clearing of infections without interacting with the microbes. We welcome manuscripts with unmodified peptides but also peptides/peptoids that are modified.
In summary, we invite manuscripts (reviews as well as original research submissions are welcome) regarding different biological functions of AMPs, for example (but not restricted to):
- Antibacterial (both Gram-negative and Gram-positive, as well as Mycobacteria)
- Synergy between AMPs and other antimicrobial compounds
- Antiviral
- Antifungal
- Antiparasitical
- Antibiofilm
- Antibacterial when attached to a surface
- Chemotactic
- Immunomodulatory