Association between host immunological and pro-inflammatory mediators with survival in cystic fibrosis patients chronically colonised with Pseudomonas aeruginosa (PA)

Introduction and Aims: Chronic PA pulmonary infection is associated with an increased host inflammatory response involving the release and activation of damaging inflammatory mediators. Quantification of these mediators may give an indication of lung damage and changes in clinical status and mortality outcome. The aim of this study was to determine whether serum IgG and IgA titre against PA in clinically stable, chronically colonised adult CF patients (n = 40) correlates with mortality and host inflammatory mediators.
Methods: Serum was assayed by ELISA for IgG and IgA against PA antigens. Sputum HNE, Cathepsin S and Cathepsin B were measured by spectrophotometric and fluorogenic assays with sputum IL-8 and TNFa, plasma IL-6 and urine TNFr1 measured by ELISA. Correlations were calculated between inflammatory mediators and antibody titre and results compared with a 10-year survival outcome. Results: A significant positive correlation was observed between IgG and IL-6 (p = 0.0005), TNFa (p = 0.0068), TNFr1 (p = 0.037), Cat S (p = 0.0106) and Cat B (p = 0.0006). No correlation was found between IgG and IL-8 or HNE (p = 0.6229, 0.3921 respectively). In addition, IL-6 levels positively correlated with mortality (p = 0.037). No correlations were found between IgA and any of the inflammatory mediators.
Conclusion: Increases in IgG titre and IL-6 levels were shown to be associated with 10 year mortality. Pro-inflammatory mediators correlated with IgG response, and suggest that IgG to PA is an immunological marker of chronic infection and survival.