Exploring the therapeutic potential of recombinant bovine β-defensins for antimicrobial and anti-inflammatory functions in sepsis management

Abstract β-defensins are multifunctional peptides of the host immune system involved in responses to infectious diseases. We investigated the potential of five recombinant proteins based on bovine β-defensins (bovine neutrophil β-defensins (BNBD) 1, 2, 3, and 4, and the tracheal antimicrobial peptide (TAP)) in functions relevant to sepsis such as antimicrobial activity, lipopolysaccharide (LPS) binding and neutralisation, and the stimulation of cytokine response in epithelial cells. These β-defensins were produced in Lactococcus lactis as fusion proteins. Antimicrobial activity was tested against Escherichia coli; LPS binding and neutralisation were assessed using a fluorescent probe displacement assay and by measuring tumour necrosis factor alpha (TNFα) levels in whole blood after an LPS challenge, respectively. Interleukin-8 (IL-8) levels were quantified to evaluate the epithelial immune response. All β-defensins exhibited different properties, suggesting they may have distinct mechanisms and functions in resolving infections. The recombinant BNBD4 showed potent antimicrobial activity against E. coli, whereas TAP was more notable for its ability to bind and neutralise LPS. These findings suggest that β-defensins, particularly BNBD4 and TAP, may be utilised to treat sepsis by targeting bacterial pathogens and modulating inflammatory responses.