Antibodies to proteases and exotoxin A of Pseudomonas aeruginosa in patients with cystic fibrosis: Demonstration by radioimmunoassay.

Sera from 33 patients with cystic fibrosis and two pediatric patients being 
treated for chronic pulmonary infections not related to cystic fibrosis and 
six sera or serum pools from uninfected individuals were tested with 
a microtiter radioimmunoassay for reactivity against exotoxin A and two proteases 
from Pseudomonas aeruginosa. Exotoxin A was purified from a low-protease strain 
of P. aeruginosa and shown to have adenosine diphosphate-ribose transferase activity 
and mouse lethality. Proteases were purified from an isolate of P. 
aeruginosa from a patient with cystic fibrosis and had proteolytic activity 
against elastin and collagen in an assay employing dimethylated protein substrates. 
The antibody responses of the patients detected using 125I-labeled antibody to 
human immunoglobulin were correlated with clinical evaluations expressed as a composite 
score based on pulmonary findings, case histories, growth and nutrition, and 
chest X rays. Values in the radioimmunoassay for patients' sera were 
compared with those of a control serum pool and expressed as 
the ratio of counts per minute (cpm) in patient serum to 
the cpm in the control pool. Inverse correlations were found between 
these ratios for each of the pseudomonas exoproducts and clinical scores; 
highest ratios occurred in patients showing the lowest clinical scores. These 
results confirm that proteases and exotoxin A of P. aeruginosa are 
produced in cystic fibrosis pulmonary infections due to P. aeruginosa and 
suggest that they may serve as significant virulence factors in these 
chronic infectious states. 