Research Only Immune & Anti-Inflammatory

hBD-3

also known as: human β-defensin 3, DEFB103A, DEFB103, defensin β3, hBD3

The broad-spectrum β-defensin — active against Gram-positive, Gram-negative and fungal targets, and largely salt-insensitive (unlike hBD-1). Isolated independently in 2001 by Harder et al. and by García et al. from psoriatic skin and tonsil respectively. The β-defensin most studied for clinical translation because of its salt tolerance.

A 45-amino-acid cationic β-defensin with a net charge of +11 — the most cationic of the major human β-defensins — isolated independently in 2001 by Harder, Bartels, Christophers and Schröder (from psoriatic scale) and by García, Jaumann, Schulz, Krause, Rodríguez-Jiménez, Forssmann, Adermann, Klüver, Vogelmeier, Becker, Hedrich, Forssmann and Bals (from tonsil tissue). Its combination of broad microbicidal spectrum, salt-insensitive activity (retains potency at physiological NaCl), and activity against antibiotic-resistant pathogens (MRSA, VRE) has made hBD-3 the β-defensin most studied for therapeutic translation, though no approved product has emerged.

Mechanism of action

Classical β-defensin mechanism — cationic membrane permeabilisation — but with several features that distinguish it from hBD-1 and hBD-2. (1) The very high net positive charge (+11) drives efficient membrane binding even at physiological ionic strength, overcoming the salt-sensitivity that limits hBD-1/2 activity in vivo. (2) Broad spectrum in vitro includes Gram-positive bacteria (S. aureus including MRSA, E. faecium including VRE, S. pneumoniae), Gram-negative bacteria (P. aeruginosa, K. pneumoniae, E. coli), fungi (C. albicans), and some enveloped viruses. (3) Dimerisation via hydrophobic interfaces contributes to the pore-forming mechanism and to immunological signalling. Beyond microbicidal activity, hBD-3 is chemotactic via CCR2 (distinct from hBD-2 which uses CCR6), activates monocytes and macrophages through TLR1/TLR2 signalling, and contributes to keratinocyte migration during wound healing. Inducible by similar stimuli to hBD-2 (IL-1β, TNF-α, IL-17, TLR ligands).

Primary uses

  • Research reagent for antimicrobial peptide studies
  • Preclinical and early-clinical antimicrobial drug development (MRSA, VRE, catheter infection, burn wound)
  • Epithelial immunity and wound-healing research
  • Clinical biomarker research (airway, saliva, oral mucosa)

Typical dosing

Not established

⚠ No human dosing established. hBD-3 has been evaluated preclinically and in very early clinical work but is not an approved therapeutic.

Regulatory status

Not a drug. hBD-3 has been the subject of multiple preclinical and early-clinical efforts at therapeutic development (topical formulations for MRSA skin infection, catheter-associated infection prophylaxis, burns), none of which have advanced to FDA approval as of 2026. Copy number variation at DEFB103A in the 8p23.1 β-defensin cluster contributes to individual differences in expression levels.

References

  1. [pubmed] Harder J, Bartels J, Christophers E, Schröder JM. "Isolation and characterization of human beta-defensin-3, a novel human inducible peptide antibiotic." J Biol Chem, 2001;276(8):5707-5713.
  2. [pubmed] García JR, Krause A, Schulz S, et al. "Human beta-defensin 4: a novel inducible peptide with a specific salt-sensitive spectrum of antimicrobial activity." FASEB J, 2001;15(10):1819-1821. (Early companion β-defensin literature contextualising hBD-3 salt-tolerance.)
  3. [pubmed] Röhrl J, Yang D, Oppenheim JJ, Hehlgans T. "Human beta-defensin 2 and 3 and their mouse orthologs induce chemotaxis through interaction with CCR2." J Immunol, 2010;184(12):6688-6694.

Related peptides

hBD-1

The constitutive epithelial β-defensin — first isolated from haemodialysate urine by Bensch, Schröder and colleagues (FEBS Letters 1995). Constitutively expressed (unlike hBD-2 and hBD-3, which are inducible), salt-sensitive in standard assays, and a major component of urogenital and airway surface antimicrobial defense.

hBD-2

The inducible β-defensin — cloned by Harder, Bartels, Christophers and Schröder (Nature 1997) from the lesional scales of psoriasis patients, with the paper framing psoriatic skin as a paradoxical "almost-never-infected" phenotype driven by massive β-defensin induction. Induced by TLR / NF-κB signalling in response to bacterial lipopolysaccharide and pro-inflammatory cytokines (IL-1, TNF-α).

HNP-1

The prototype human α-defensin — isolated from neutrophil granules by Ganz, Selsted and Lehrer in 1985; the dominant antimicrobial peptide in human neutrophils and a workhorse molecule of innate immunity. Research peptide only: no defensin has ever been developed as an approved drug.

HD5

The Paneth cell α-defensin — the dominant antimicrobial peptide of the human small intestine, stored at millimolar concentrations in Paneth cell secretory granules and released into the crypt lumen upon cholinergic or bacterial stimulus. Reduced HD5 expression is a recognised feature of ileal Crohn disease.

HD6

The Paneth cell α-defensin that does not kill directly — HD6 traps enteric pathogens by self-assembling into fibrillar "nanonets" (Chu et al., Science 2012), a mechanism unique among the defensin family. Poor microbicidal activity in vitro was a decade-long puzzle until the trapping mechanism was discovered.
Disclaimer

This entry is for educational purposes only and does not constitute medical advice. Dosing information reflects published regulatory or research data and is not a recommendation. Many compounds described here are not approved for human use in the United States. Consult a licensed medical professional before considering any peptide therapy.