A Review of Antimicrobial Peptides: Defensins and Related Cationic Peptides

Abstract

Cationic antimicrobial peptides are present throughout the plant and animal kingdoms and bear striking structural and functional similarities across species lines. They provide primitive, nonspecific means of combating a variety of bacteria, fungi, enveloped viruses, and protozoa. Some are also cytotoxic against host cells, including neoplastic cells. Cationic antimicrobial peptides may play various roles in inflammation and tissue repair. Antimicrobial peptides are found in epithelial tissues regularly exposed to microbial attack as well as in cells whose primary function is defense against potential pathogens. They constitute an important part of the nonoxidative antimicrobial arsenal of leukocytes. They are preformed and/or readily synthesized when the cells are stimulated by exposure to pathogens. They exert their effects directly by inserting into membranes of target cells and forming ion channels which increase membrane permeability; however, antimicrobial peptides can also act as opsonins to facilitate phagocytosis. Resistance to defensins is a virulence factor for organisms such as Salmonella sp. The study of cationic antimicrobial peptides is increasing our understanding of innate immunity, inflammation, and the pathogenesis of genetic diseases such as specific granule disease in humans. Therapeutic applications of antimicrobial peptides are currently under investigation.

Chicken cathelicidins as potent intrinsically disordered biocides with antimicrobial activity against infectious pathogens

“…Furthermore, some other roles have been described for several AMPs, especially those involved in the immune response consolidation and regulation (Finlay and Hancock, 2004). However, the primary biocidal mechanism of AMPs is killing microbes via disruption of their membrane integrity, the action that depends on two main characteristics, their cationic nature and amphipathicity (Evans and Harmon, 1995;Powers and Hancock, 2003). In this study, we aimed to identify the expression patterns of the cathelicidin genes in a local Saudi chicken, to evaluate the antimicrobial activity of the corresponding peptides against pathogenic bacteria, and to monitor the changes in their antimicrobial activity by using amidated analogs of these peptides.…”

Bovine polymorphonuclear cells passively acquire membrane lipids and integral membrane proteins from apoptotic and necrotic cells

“…However, the role of PMNs within the immune system may be much broader. For example, PMN-derived cationic peptides can influence cell trafficking and dendritic cell (DC) activation [1], and PMNs have also been shown to express an impressive assortment of proteins and cytokines such as complement receptor 1 (CR1), CR3, Fc receptor, interferon-␣ (IFN-␣), interleukin (IL)-1, IL-3, IL-8, and tumor necrosis factor ␣ [2]. Thus, PMNs are transcriptionally active and have the potential to vary in their responses to a broad range of innate immune stimuli.…”

Neutrophils efficiently cross-prime naive T cells in vivo

“…17,18 (1) Activated neutrophils modulate DC maturation [18][19][20][21] and trafficking. 22,23 (2) Infected neutrophils may serve as substrates for antigen cross-presentation by DCs. 24 (3) Activated neutrophils acquire the expression of MHC II molecules, costimulatory molecules (such as CD80 in mouse and CD86 and CD80 in human), 25,26 and the DC maturation marker CD83 27 and present in vitro antigens into MHC II molecules to memory CD4 ϩ T cells.…”