Defensin and Related Antimicrobial Peptides - NEWLY UPDATED!
Defensin peptides have broad-spectrum microbicidal effects against a number of microorganisms that include bacteria, envelop viruses, fungi, spirochetes and mycobacteria. To date, six human α-defensins are classified into two sub-groups: human neutrophil peptides (HNP- 1 to HNP-4) and human defensins (HD-5 and HD-6) which are predominantly expressed in Paneth cells of the ileum.
HNP-1 to HNP-3 (PDF-4271-s, PDF-4428-s, and PDF-4416-s) are cationic peptides composed of 29-35 amino acids, and their amino acid sequences are identical except for the first residue at the N-terminus. These α-defensins are stored in the azurophilic granules of human neutrophils.1,2 Following cell activation, these agents are released into phagolysosomes containing ingested mi- crobes where they bind and permeabilize the lipid bilayer of the microbes. Other activities include IL-8 secretion,3 chemoattrac- tant activity,4,5 and mitogenic effects on fibroblast, epithelial and carcinoma cells. 6,7 Lundy and colleagues found over expression of HNPs 1-3 in squamous cell carcinoma and gingival crevicular fluid from dental patients implying a role in host defense, HNP 1 being the most abundant followed by HNP 2 and 3.7, 8 However, Muller’s previous study suggests α-defensins may be involved in the pathogenesis of renal tumors.9 Other studies indicate that these defensins are lectins capable of binding to gp120 and CD4, surface receptors responsible for HIV-1 entry into cells.10 HNPs 1-3 were also shown to block papillomavirus infection and neu- tralize anthrax toxin, with all three subgroups exhibiting similar activity.11,12 Peptides International now offers α-defensin-2 or HNP-2 (PDF-4428-s) along with our current line of α-defensin products.
HD-5 (PDF-4415-s) is expressed in Paneth cells in intestinal epithelium, and thus, falls into a distinct subclass of human α-defensin.13,14 In transgenic mouse models, it was confirmed that HD-5 expression was specific to Paneth cells and resulted in resistance to bacterial challenge.15 In patients with HIV-related cryptosporidiosis, HD-5 immunoreactivity was reduced in as- sociation with Paneth cell granule depletion.16 In inflammatory bowel disease, HD-5 was expressed in metaplastic Paneth cells in the colon.17 Based on these findings, HD-5 could be an essential factor in the defense against intestinal inflammation.