A novel neutrophil derived inflammatory biomarker of pulmonary exacerbation in cystic fibrosis.

ABSTRACT

BACKGROUND: The focus of this study was to characterize a novel biomarker for cystic fibrosis (CF) that could reflect exacerbations of the disease and could be useful for therapeutic stratification of patients, or for testing of potential drug treatments. This study focused exclusively on a protein complex containing alpha-1 antitrypsin and CD16b (AATCD16b) which is released into the bloodstream from membranes of pro-inflammatory primed neutrophils. METHODS: Neutrophil membrane expression and extracellular levels of AAT and CD16b were quantified by flow cytometry, Western blot analysis and by 2D-PAGE. Interleukin-8 (IL-8), tumor necrosis factor-alpha (TNF-alpha) and AATCD16b complex were quantified in CF plasma (n=38), samples post antibiotic treatment for 14 days (n=10), chronic obstructive pulmonary disease (n=10), AAT deficient (n=10) and healthy control (n=14) plasma samples by ELISA. RESULTS: Cell priming with IL-8 and TNF-alpha caused release of the AATCD16b complex from the neutrophil cell membrane. Circulating plasma levels of IL-8, TNF-alpha and AATCD16b complex were significantly higher in patients with CF than in the other patient groups or healthy controls (P<0.05). Antibiotic treatment of pulmonary exacerbation in patients with CF led to decreased plasma protein concentrations of AATCD16b complex with a significant correlation with improved FEV1 (r=0.81, P=0.003). CONCLUSION: The results of this study have shown that levels of AATCD16b complex present in plasma correlate to the inflammatory status of patients. The AATCD16b biomarker may become a useful addition to the clinical diagnosis of exacerbations in CF.