Distribution of Antibodies to Selected Antigens of Pseudomonas aeruginosa in Children and Young Adults with Cystic Fibrosis

Introduction: Eradication of Pseudomonas aeruginosa (P.a.) in patients with cystic fibrosis (CF) is possible if it is initiated in the early course of infection. Therefore, the detection of P.a. as early as possible is an important goal of care. Regular determination of antibodies to P.a. antigens in serum may be useful in patients who have not yet been infected or were infected intermittently. The aim of the present study was to assess the concentrations of antibodies to selected antigens of P. aeruginosa in the serum of children with CF and with known status of P.a. infection. Material and Methods: The study was performed in 111 CF patients (27 not infected with P. aeruginosa, 29 with intermittent infection and 55 with chronic infection). The concentrations of IgG antibodies to the alkaline protease (AP), elastase (ELA) and exotoxin A (Exo-A) were measured. The increased concentration of antibodies was defined as exceeding 500 units (according to the manufacturer). The results of antibodies assessment were analysed according to previous infection status and the results of present culture. Results: At the time of the study, P.a. was cultured from sputum of 57 patients: 9 out of 29 (31%) with intermittent infection, and 48 out of 55 (87%) with chronic infection. Increased concentrations of antibodies to one or more P.a. antigens were found in 60 patients, and to all three types of antigens in 30 patients. Increased serum antibody concentration was found significantly more often in the patients with chronic P.a. infection compared to those with intermittent infection (82% vs. 35%, p = 0.0001). In the patients with chronic P.a. infection (especially with mucoid type), serum antibody concentrations were significantly higher than in other patients. Higher concentrations of antibodies were also found in the patients with positive result of P.a. culture at the time of the study, compared to those with negative culture. In 19% of patients not infected with P.a., increased serum antibodies to at least one P.a. antigen were found. The clinical significance of such findings is unclear and needs further investigation. Conclusions: In the present study, the increased serum concentrations of IgG antibodies to P. aeruginosa antigens (AP, ELA and Exo-A) were found most often in the patients with chronic P.a. infection and in those in whom P.a. (especially mucoid type) was cultured at the time of the study. The clinical significance of the elevated antipseudomonal antibodies level in 19% of the patients never infected with P.a. is unclear and needs further investigation.