Antimicrobial peptides

About: Antimicrobial peptides is a research topic. Over the lifetime, 10645 publications have been published within this topic receiving 507688 citations. The topic is also known as: host defense peptide & antimicrobial protein.

Epithelial antimicrobial peptides: innate local host response elements.

Abstract: Multicellular organisms have to survive in an environment laden with numerous microorganisms, which represent a potential hazard to life. Different strategies have been developed to ward off infections by preventing microorganisms from entering surfaces and by preventing the attack of microorganisms that have already entered the epithelia. Therefore, it is not surprising that epithelia are equipped with various antimicrobial substances that act rapidly to kill a broad range of microorganisms. This review summarizes our present knowledge about epithelial peptide antibiotics produced in plants, invertebrates, and vertebrates including humans. There is now strong evidence that in addition to constitutively secreted peptide antibiotics, others are induced upon contact with microorganisms or by proinflammatory cytokines. β-Defensins represent one family of vertebrate antimicrobial peptides, members of which are inducible and have recently been identified in humans. The defensin-characteristic local expression pattern may indicate that specialized surfaces express a characteristic surface antimicrobial peptide pattern that might define the characteristic microflora as well as the density of microorganisms present on the surface.

The role of mucosal immunity and host genetics in defining intestinal commensal bacteria.

Abstract: Purpose of review Dramatic advances in molecular characterization of the largely noncultivable enteric microbiota have facilitated better understanding of the composition of this complex ecosystem at broad phylogenetic levels. This review outlines current understanding of mechanisms by which commensal bacteria are controlled and shaped into functional communities by innate and adaptive immune responses, antimicrobial peptides produced by epithelial cells and host genetic factors.

Expression and regulation of antimicrobial peptides in the gastrointestinal tract

Abstract: The gastrointestinal (GI) tract is exposed to a wide range of microorganisms. The expression of antimicrobial peptides has been demonstrated in different regions of the GI tract, predominantly in epithelial cells, which represent the first host cells with which the microorganisms have to interact for invasion. The intestinal epithelial monolayer is complex, consisting of different cell types, and most have a limited lifespan. Of the GI antimicrobial peptides, alpha- and beta-defensins have been studied the most and are expressed by distinct types of epithelial cells. Enteric alpha-defensin expression is normally restricted to Paneth and intermediate cells in the small intestine. However, there are important differences between mice and humans in the processing of the precursor forms of enteric alpha-defensins. Parasite infection induces an increase in the number of enteric alpha-defensin-expressing Paneth and intermediate cells in the murine small intestine. In the chronically inflamed colonic mucosa, metaplastic Paneth cells (which are absent in the normal colon) also express enteric alpha-defensins. Epithelial expression of beta-defensins may be constitutive or inducible by infectious and inflammatory stimuli. The production of some members of the beta-defensin family appears to be restricted to distinct parts of the GI tract. Recent studies using genetically manipulated rodents have demonstrated the likely in vivo importance of enteric antimicrobial peptides in innate host defense against microorganisms. The ability of these peptides to act as chemoattractants for cells of the innate- and adaptive-immune system may also play an important role in perpetuating chronic inflammation in the GI tract.

β-Amyloid peptides display protective activity against the human Alzheimer’s disease-associated herpes simplex virus-1

Abstract: Amyloid plaques, the hallmark of Alzheimer’s disease (AD), contain fibrillar β-amyloid (Aβ) 1-40 and 1-42 peptides. Herpes simplex virus 1 (HSV-1) has been implicated as a risk factor for AD and found to co-localize within amyloid plaques. Aβ 1-40 and Aβ 1-42 display anti-bacterial, anti-yeast and anti-viral activities. Here, fibroblast, epithelial and neuronal cell lines were exposed to Aβ 1-40 or Aβ 1-42 and challenged with HSV-1. Quantitative analysis revealed that Aβ 1-40 and Aβ 1-42 inhibited HSV-1 replication when added 2 h prior to or concomitantly with virus challenge, but not when added 2 or 6 h after virus addition. In contrast, Aβ 1-40 and Aβ 1-42 did not prevent replication of the non-enveloped human adenovirus. In comparison, antimicrobial peptide LL-37 prevented HSV-1 infection independently of its sequence of addition. Our findings showed also that Aβ 1-40 and Aβ 1-42 acted directly on HSV-1 in a cell-free system and prevented viral entry into cells. The sequence homology between Aβ and a proximal transmembrane region of HSV-1 glycoprotein B suggested that Aβ interference with HSV-1 replication could involve its insertion into the HSV-1 envelope. Our data suggest that Aβ peptides represent a novel class of antimicrobial peptides that protect against neurotropic enveloped virus infections such as HSV-1. Overproduction of Aβ peptide to protect against latent herpes viruses and eventually against other infections, may contribute to amyloid plaque formation, and partially explain why brain infections play a pathogenic role in the progression of the sporadic form of AD.