Antimicrobial peptides, disease severity and exacerbations in bronchiectasis

Area of Science:

• Pulmonary Medicine
• Immunology
• Microbiology

Background:

• Frequent exacerbations are a key phenotype in bronchiectasis, but underlying biological mechanisms remain unclear.
• Antimicrobial peptides (AMPs) play a role in host defense but can promote inflammation in chronic lung diseases.

Purpose of the Study:

• To investigate pulmonary and systemic levels of AMPs in bronchiectasis.
• To determine the relationship between AMP levels, disease severity, and future exacerbation risk.

Main Methods:

• Prospective enrollment of 135 adult bronchiectasis patients across three European centers.
• Quantification of cathelicidin LL-37, lactoferrin, lysozyme, and secretory leukocyte protease inhibitor (SLPI) in serum and sputum using ELISA.
• 12-month follow-up to assess the predictive ability of sputum AMPs for future exacerbation risk.

Main Results:

• Sputum AMP levels were higher than serum levels, indicating local release.
• Patients with more severe bronchiectasis exhibited dysregulated airway AMP levels.
• Elevated LL-37 and reduced SLPI levels correlated with higher Bronchiectasis Severity Index, lower FEV1, and Pseudomonas aeruginosa infection.
• Low SLPI levels were associated with baseline exacerbation frequency.
• Higher LL-37 and lower SLPI levels predicted shorter time to next exacerbation, with LL-37 alone predicting 12-month exacerbation frequency.

Conclusions:

• Bronchiectasis patients, particularly those with frequent exacerbations, display dysregulated sputum AMP levels, notably elevated LL-37 and reduced SLPI.
• These altered AMP levels are linked to Pseudomonas aeruginosa infection.
• Elevated LL-37 and reduced SLPI serve as predictive markers for future exacerbations in bronchiectasis.