Neutrophil defensin 3

Also known as: Defensin, alpha 3, HNP-3, DEFA3, P59666

**Mechanism of Action** Neutrophil defensin 3 (HNP-3) is a cationic antimicrobial peptide stored in azurophilic granules of neutrophils. It exerts broad-spectrum antimicrobial activity by disrupting microbial membranes through electrostatic interactions with negatively charged phospholipids, leading to pore formation and cell lysis. Additionally, HNP-3 modulates host immune responses by promoting chemotaxis, activating complement, and enhancing phagocytosis, while also exhibiting antiviral effects via direct binding to viral envelopes. **Key Research Findings** Preclinical studies demonstrate HNP-3’s efficacy against Gram-positive and Gram-negative bacteria (e.g., *Staphylococcus aureus*, *Escherichia coli*), fungi (e.g., *Candida albicans*), and enveloped viruses (e.g., HIV-1, herpes simplex virus). Its activity is salt-sensitive and concentration-dependent, with optimal function at physiological pH. Research also highlights its role in wound healing and inflammation regulation, though cytotoxicity at high doses limits therapeutic application. **Clinical Relevance** HNP-3 remains in the experimental stage, with no approved clinical indications. Its potential as an adjunctive therapy for antibiotic-resistant infections or as an immunomodulatory agent is under investigation, but challenges include stability, delivery, and off-target effects. Current evidence is limited to *in vitro* and animal models. For research purposes only — not medical advice.

Key data

Mechanism of action

Effector molecule of the innate immune system that acts via antibiotic-like properties against a broad array of infectious agents including bacteria, fungi, and viruses (PubMed:15616305, PubMed:15772169, PubMed:17142766). Possesses the ability to neutralize bacterial toxins such as B.anthracis lethal factor, Clostridium difficile cytotoxin B as well as leukocidin produced by Staphylococcus aureus (PubMed:15772169, PubMed:18435932, PubMed:25963798). Also blocks herpes simplex virus infection by interacting with envelope glycoprotein B and thus preventing its binding to heparan sulfate, the receptor for attachment (PubMed:17142766)

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