Human IgG antibodies to Pseudomonas aeruginosa core lipopolysaccharide determinants are detected in chronic but not acute pseudomonas infection.

Human IgG response to Pseudomonas aeruginosa core lipopolysaccharide determinants was measured after both acute and chronic pseudomonas infection by using lipopolysaccharide purified from PAC605 cells (the most lipopolysaccharide-defective or "roughest" mutant of P. aeruginosa yet described) as a solid phase antigen in ELISA and Western blot immunoassay. The geometric mean IgG anti-PAC605 lipopolysaccharide titer of sera from 18 cystic fibrosis (CF) patients with chronic pseudomonas pulmonary infection was 1808, compared to 171 for convalescent sera of 10 patients with acute pseudomonas bacteremia (p less than 0.001) and 211 for 5 normal human volunteers (p less than 0.001). Western blot immunoassay demonstrated specific IgG anti-core antibodies in 11/18 sera from CF patients but not in the sera of the convalescent bacteremic patients or normal volunteers. IgG anti-Pseudomonas core lipopolysaccharide antibodies appear to be a marker of chronic infection; the possible protective role of these antibodies remains to be established.