Supplementary Material for: Expression of MIG/CXCL9 in Cystic Fibrosis and Modulation of Its Activities by Elastase of <b><i>Pseudomonas aeruginosa</i></b>

In cystic fibrosis (CF), colonization of the airways with <i>Pseudomonas aeruginosa </i>is associated with disease deterioration. The mechanism behind the disease progression is not fully understood. The present work shows that the antibacterial chemokine MIG/CXCL9 is present in the airways and in sputum of CF patients. MIG/CXCL9 showed high bactericidal activity against. <i>P. aeruginosa, </i>including some strains from the airways of CF patients. Full-length MIG/CXCL9 was detected in sputum from healthy controls and CF patients colonized with <i>P. aeruginosa. </i>However, degraded MIG/CXCL9 was only found in CF sputum. In vitro, elastase of <i>P. aeruginosa </i>cleaved off a fragment of similar size and two additional fragments from MIG/CXCL9. The fragments showed less bactericidal activity against <i>P. aeruginosa </i>compared with the full-length protein. The fragments did not activate the MIG/CXCL9 receptor CXCR3 (expressed e.g. by NK cells, mast cells, and activated T cells) but instead displayed noncompetitive inhibition. In vitro, a decrease in CXCR3-bearing cells was found within and in the proximity of the bronchial epithelium of CF lung tissue compared with controls. Taken together, both bactericidal and cell-recruiting activities of MIG/CXCL9 are corrupted by <i>P. aeruginosa </i>through release of elastase, and this may contribute to impaired airway host defense in CF.