Defenses That Are Very Similar and Very Different
Organisms have an innate immunity, or an inborn immunity, which protects against microorganism invasion. As a part of this defense, the host defense peptides (HDPs) are promising alternatives to antibiotics, given that they have a multitude of options in fighting against a variety of bacteria, envelope viruses, fungi, spirochetes, and mycobacteria. The cathelicidins are a family with the HDPs and not only do they stop the spread of these invaders, they also bolster the immune system. In humans, LL-37 is currently the only known cathelicidin, however, four have been discovered in chickens and 11 have been identified in pigs. As a result of past widespread antibiotic abuse, the livestock industry has had to look for new options in keeping their herds healthy. Perhaps the cathelicidins will be the answer.
In a new Nature Scientific Reports publication, a team, led by Maaike R. Scheenstra out of Utrecht University in the Netherlands, has tested three cathelicidins, human LL-37, chicken CATH-2, and pig myeloid antibacterial peptide 36 (PMAP-36). All three effectively destroy e. coli and also differ in their modes of action. Of the three, PMAP-36 was the most efficacious. Lipopolysaccharide (LPS) is a large component of the bacterial cell wall and all three peptides caused disruption in LPS-induced macrophage activation, with LL-37 being the most successful. The importance of the cysteine in PMAP-36 was evaluated for its significance and it was found that the formation of a dimer seemed to play a critical role in its immunomodulatory activity. Read more about this interesting work in the reference below.1
- M.R. Scheenstra et al., Scientific Reports, 9, 4780 (2019).