Antimicrobial peptides and infectious diseases

Antimicrobial peptides (AMPs) are genetically encoded, evolutionarily ancient defence molecule, which act as primary effectors of the innate immune system. Although their origin dates back to the 1920s, research on AMPs has gained momentum relatively recently after the discovery of the underlying mechanisms of innate immunity and their modulation by AMPs. In mammals, the source of AMPs is mainly the circulating and tissue phagocytes and epithelial cells, which are engaged in the killing of the engulfed pathogens and preventing tissue colonization, respectively. Direct microbicidal function of AMPs in vitro encompasses a broad range of Gram-positive and Gram-negative bacteria including multidrug resistant organisms, fungi, viruses and protozoal parasites. Their unique mechanism of action minimises the risk of drug resistance, hence their potential as alternatives or adjuncts to classical antibiotics is under active investigation. Apart from the microbicidal activities, multiple immunomodulatory properties, such chemotaxis, activation of immature dendritic cells, lipopolysaccharide blockage, angiogenesis and cytokine induction are critical attributes to AMPs and believed to be the principal modes of action of AMPs in infectious diseases.