Detection by enzyme-linked immunosorbent assays of antibody specific for Pseudomonas proteases and exotoxin A in sera from cystic fibrosis patients.

Enzyme-linked immunosorbent assays were developed to measure serum antibody specific for Pseudomonas elastase, alkaline protease, and exotoxin A. Antibody responses to each Pseudomonas antigen were measured in cystic fibrosis (CF) patients who were not colonized with Pseudomonas aeruginosa, in those who were colonized, in those who were chronically infected with this organism, and in control subjects. Antibody levels for each antigen in the colonized and infected CF patients were higher than levels in uncolonized CF patients or non-CF control subjects. The antibody responses to elastase were similar in patients of the colonized and infected groups. However, infected CF patients had significantly elevated levels of antibody to exotoxin A (P less than 0.01) and alkaline protease (P less than 0.05) when compared with patients simply colonized with P. aeruginosa. These findings confirm that Pseudomonas alkaline protease, elastase, and exotoxin A are produced by Pseudomonas strains which colonize and infect CF patients. As an adjunct to established procedures (X-ray, microbiological culture, etc.), the antitoxin and anti-protease enzyme-linked immunosorbent assays may be clinically useful tests for differentiating colonized CF patients from those who have more severe Pseudomonas pulmonary infections.