Autoantibodies against bactericidal/permeability-increasing protein (BPI-ANCA) in cystic fibrosis patients treated with azithromycin

Autoantibodies against bactericidal/permeability-increasing protein (BPI-ANCA) were found in patients with cystic fibrosis (CF). It is speculated that they represent a marker of the chronic endobronchial infection and sustained inflammatory response in CF. Our aim was to evaluate whether azithromycin (AZM), through its anti-inflammatory effect, could affect the level of BPI-ANCA in CF patients. Eighteen patients with CF aged 5.5-36.3 years (median 15.1) were enrolled in a randomised, double-blind, placebo-controlled trial of AZM (250 mg twice a week to 10 patients) or placebo (8 patients) for 12 weeks. BPI-ANCA levels were recorded pre- and post-treatment and compared to a group of 18 matched healthy controls. Chi-square analysis, Kruskal-Wallis and Mann-Whitney tests were used to compare between the groups. Pre- and post-treatment values were compared using the Wilcoxon Signed-Ranked test. BPI-ANCA was found in 12 CF patients (67%) and four (22%) healthy subjects (P<0.001). The mean BPI-ANCA level was 3.94±6.15 U/ml (mean±SD) in healthy subjects and 38.11±42.34 U/ml in CF patients (P=0.023). The mean BPI-ANCA level was higher in patients with Pseudomonas aeruginosa compared to those without (64±35 U/ml and 25±41 U/ml respectively, P=0.032). No change in BPI-ANCA levels occurred in the AZM-treated patients [35 (0-127) U/ml (median (range) and 30 (0-120) U/ml, respectively] or in the placebo group [10 (0-66) U/ml and 13 (0-83) U/ml, respectively]. BPI-ANCA levels are significantly higher in patients with CF compared to healthy controls. BPI-ANCA levels are higher among patients colonised with P. aeruginosa. Twelve weeks of AZM therapy did not lower the BPI-ANCA level in patients with CF.