Prognostic factors in cystic fibrosis - the impact of antibody response and platelet activation

The prognosis in cystic fibrosis (CF) has improved dramatically over the last decades, but the clinical course is variable. Many factors influence prognosis, and colonisation with Pseudomonas aeruginosa is one of them. Earlier studies have shown that patients with P. aeruginosa who have developed anti-neutrophil cytoplasmic antibodies specific for BPI, bactericidal/permeability-increasing protein (BPI-ANCA), have worse prognosis. Platelets are involved in the immune response in acute and chronic inflammation, but their role in CF is not well studied. The overall aim of this thesis is to evaluate BPI-ANCA as a prognostic factor, investigate why BPI-ANCA is formed and investigate platelet activation in CF in general and in association with BPI-ANCA. (I) Long time prognosis in 46 adult CF patients was studied. BPI-ANCA was measured at inclusion and evaluated, over a ten year period, together with lung function and P. aeruginosa colonisation. BPI-ANCA correlated significantly to outcome, stronger than colonisation status. Lung function at inclusion was also a very important predictor. II): The relation between BPI-ANCA and three P. aeruginosa serology tests was investigated in 117 CF patients. There was only a week correlation between serologies and BPI-ANCA and BPI-ANCA had a higher capability of predicting end-points. All tests identified chronic colonisation but none of them predicted future colonization. (III): In order to study if molecular charachteristics of different P. aeruginosa strains determine if BPI-ANCA develops, two screening methods were employed. Strains from BPI-ANCA negative and BPI-ANCA positive patients were compared using mRNA microarray and 2D gel electrophoresis on outer membrane fractions. Both methods suggested that expression of flagellin A could be related to the development of BPI-ANCA. However, analysis on the gene level using PCR in a cohort of 37 CF patients did not confirm this assumption. (IV): Platelet activation occurs during infection and inflammation. Activated platelets bind to and modulate monocytes and neutrophils and influence the inflammatory processes. Increased platelet activation has been seen in CF. Platelet function in plasma from 22 CF patients was compared with healthy controls. Platelet aggregation, platelet activation, platelet-leukocyte complex formation, and leukocyte activation were analysed. We confirm that platelet activation is increased in CF patients. Increased platelet aggregation and platelet-monocyte activation was observed but clearly activated isolated platelets were not detected in ex-vivo samples. Levels of platelet/monocyte complex formation correlate with lung function decline, CRP and BPI-ANCA (IgG and IgA). The increased reactivity measured by AUC collagen indicates in-vivo priming of the platelets and it also correlates with BPIANCA. Conclusions: The results from study I and II both show that BPI-ANCA is a stronger prognostic factor than P. aeruginosa colonisation on its own and we suggest that it is a marker of a negative host-pathogen interaction. Flagellin expression is possibly involved in the generation of BPI-ANCA, but ist is not only the expression of flagellin A that matters as there are many differences between bacteria in BPI-ANCA positive and negative patients. Platelets are activated in CF plasma, and this correlates with clinical findings in the patients.