Antimicrobial polypeptides

Abstract

The respiratory tract presents a large and potentially vulnerable surface to inhaled microbes. It is coated by a thin layer of secretions generated by airway epithelial cells, submucosal glands, resident and recruited phagocytes (neutrophils, eosinophils, monocytes, and macrophages) and alveolar epithelial cells, as well as substances that enter from blood plasma. More than 80 years ago, Alexander Fleming observed that respiratory secretions have microbicidal and microbistatic properties. He described the activity of lysozyme, one of the principal polypeptides of these secretions. Since then, a number of additional antimicrobial components have been identified, and there is increasing insight into their complex interactions. This review is an update of my previous summary of this area.

pH modulates the activity and synergism of the airway surface liquid antimicrobials β-defensin-3 and LL-37

“…In the mammalian respiratory system, the interface between the environment and the organism is a thin layer of airway surface liquid (ASL). To maintain sterile lungs and protect against bombardment with bacteria, mammalian lungs have evolved multiple protective mechanisms, one of which is antimicrobials in ASL that rapidly kill inhaled and aspirated bacteria (5)(6)(7)(8)(9).…”

Truncation of the Lipopolysaccharide Outer Core Affects Susceptibility to Antimicrobial Peptides and Virulence of Actinobacillus pleuropneumoniae Serotype 1

“…We sought to examine if a defined mutation within the LPS could result in a decrease in LPSinduced cytokine production and consequently cause an attenuation of the virulence of A. pleuropneumoniae. One other important component of the innate immune system is antimicrobial peptides, which can either be released by epithelial cells or by phagocytic cells (25). Most of these peptides are small cationic peptides that have been isolated from various biological sources (26); they act mainly by forming pores in bacterial membranes (27).…”

Characterization of Released Polypeptides During an Interferon-γ-Dependent Antibacterial Response in Airway Epithelial Cells

“…synergistically with other AMPs with respect to bactericidal effect others 1999, 2002;Singh and others 2000;Ganz 2004). Consequently, the antibacterial potential of the incubation medium may not be correctly reflected by additive effects of various AMPs, but several synergistic effects are likely to be present.…”

“…The latter is a feature that, together with intermingled hydrophobic amino acid residues, results in domains with an amphipathic secondary structure. This structure provides a propensity to disrupt bacterial membranes (Hancock and Diamond 2000;Boman 2003;Ganz 2004). However, there may be other targets in bacteria, for example, mechanisms resulting in bacteriostatic effects, such as depletion of iron in the case of neutrophil gelatinase-associated lipocalin (NGAL) (Borregaard and Cowland 2006).…”