Reaction of antibody in sera from cystic fibrosis patients with nontoxic forms ofPseudomonas aeruginosa exotoxin A

Sera from 48 cystic fibrosis patients from two hospitals were screened for antibody against rods, non-toxic macromolecular structures which share antigenic determinants withPseudomonas aeruginosa exotoxin A. A solid-phase radioimmunoassay employing (¹²⁵I)-staphylococcal protein A was used to detect anti-rod IgG. Antibodies recognizing rods, exotoxin A, or both antigens, were demonstrated using a competitive radioimmunoassay in cystic fibrosis patient sera, and in sera from animals immunized with exotoxin A, rods, or infected withPseudomonas aeruginosa. Anti-rod titers of cystic fibrosis patients (1.07 to 14 x control serum levels) inversely correlated with aggregate clinical evaluation scores, and in most instances, with X-ray scores. Since rods are non-toxic and cross-reactive with exotoxin A, they may represent therapeutically useful antigens for producing immunity to exotoxin A.