IgG response in cystic fibrosis patients colonised with transmissible and non-transmissible Pseudomonas aeruginosa

Introduction and Aims: Some transmissible strains of P. aeruginosa are more virulent than non-transmissible strains and stimulate a heightened immunological response. The aim of this study was to compare IgG titre against P. aeruginosa antigens in clinically stable adult CF patients colonised with either transmissible (n = 20 patients) or non-transmissible strains (n = 20 patients).
Methods: Serum samples from clinically stable CF patients with chronic P. aerug- inosa infection were assayed by ELISA for IgG against P. aeruginosa antigens. Antibody response was correlated with other clinical and demographic parameters: CRP, white cell and neutrophil count, BMI, FEV1 and age.
Results: There was no difference detected between groups for any of the clinical and demographic parameters and groups were well matched. Furthermore, there was no significant difference in IgG response against P. aeruginosa antigens between the groups (p = 0.64). Therefore, results from both groups were combined for further statistical analysis. Positive correlations were detected between IgG and all parameters except age (p = 0.189). These correlations were highly significant between IgG and CRP (p = 0.002), neutrophil (p = 0.008) and white cell count (p=0.005). A weaker correlation was observed between IgG and FEV1 and BMI (p-values = 0.03 and 0.04 respectively).
Conclusion: During periods of clinical stability, CF patients infected with transmis- sible P. aeruginosa do not show a heightened IgG response against specific P. aerug- inosa antigens, when compared with patients colonised with non-transmissible strains. Antibody levels correlate with other systemic markers of inflammation.