Defensins (α- and β-class defensins)
Defensins are a large family of natural protective peptides that are the first to meet microbes on the skin, in the gut, and on other mucous membranes. They are studied as a basis for anti-infection creams and as vaccine helpers.
A family of 29–45 aa with 3 disulfide bonds, β-hairpin structure. α-HNP1-4 (~3.4 kDa), HD-5/HD-6 (intestinal). β-hBD1-4 (~5.2 kDa). hBD-3 is the most potent: 45 aa, active at physiological [NaCl].
The first line of immune defense of epithelial barriers. hBD-3: active against MRSA with an MIC of 1 mg/L, synergy with rifampicin. Antiviral spectrum: HIV, HSV, SARS-CoV-2. Vaccine adjuvants (↑antibody production). Regulation of the gut and reproductive tract microbiome.
Cationic peptide + anionic bacterial membrane → insertion → pore formation → osmotic lysis. Immunomodulation: chemotaxis of DCs and T lymphocytes via CCR6; ↑DC maturation; ↑IFN-γ production; adjuvant effect in vaccination.
Studies used them only topically: clinically — an α-defensin 5 + β-defensin 3 cream for a course of 12 weeks (PMID: 37683059). Systemic use is limited by rapid degradation by proteases and cytotoxicity at high concentrations.
Level B-C Human observational data. There are studies in humans, but they are small, uncontrolled, or cohort studies. The data are encouraging but need confirmation. Clinical studies in dermatology. Phase I/II antibiotics.
⚠️ Not a single peptide — a family of >30 molecules. No commercial products. Systemic use is not yet possible. Research only.
Research peptides are laboratory reagents (Research Use Only). They are not medicines and are not intended for use in humans or animals.