Antimicrobial peptides in nasal secretion and mucosa with respect to S. aureus colonisation in Wegener's granulomatosis

Objective. Nasal S. aureus carrier rates are significantly higher in patients with Wegener's granulomatosis (WG) compared to healthy controls (HC), and nasal colonisation is a risk-factor for relapse. Antimicrobial peptides (AMP) are important defence molecules maintaining an intact barrier function. It is the aim of this study to see if there is a possible link between the nasal AMP pattern and S. aureus colonisation, a link which has not been investigated so far. Patients and methods. ELISA was applied to quantify LL-37 and hBD-3 concentrations in nasal secretions (14 WG patients, 13 HC) with and without nasal S. aureus colonisation. Immunohistochemistry was used to detect the cellular sources of AMP in the nasal mucosa. Functional analyses of primary nasal epithelial cell cultures (NEC) of these groups stimulated with S. aureus were performed. Results. LL-37 was found in significantly higher concentrations in colonised individuals (WG: p=0.001; HC: p=0.014). Using immunohistochemistry, local cellular sources for AMP could be demonstrated. After stimulation with S. aureus, significantly higher concentrations of LL-37 and hBD-3 could be detected in the supernatant of NEC of WG patients (LL-37: p=0.001; hBD-3: p=0.001) and HC (LL-37: p=0.019; hBD-3: p=0.001). HBD-3 concentrations were significantly lower in the supernatant of stimulated NEC of WG patients compared to the NEC of HC (p=0.032), and the dynamic range of the hBD-3 answer was significantly smaller in WG compared to HC (p=0.016). Conclusion. The dynamic response towards challenges with microbes is dysregulated in WG, and this might be one reason for higher S. aureus colonisation rates in WG.