Immune response in cystic fibrosis to outer membrane proteins of Pseudomonas aeruginosa

The systemic humoral immune response in cystic fibrosis (CF) to outer membrane (OM) proteins of Pseudomonas aeruginosa was investigated as a function of the time of colonization by immunoblotting. OM proteins were prepared from bacteria grown in ion-sufficient, magnesium-depleted, and iron-deficient media. The location of proteins F, H, and I on the blots was verified by monoclonal antibodies. Proteins H2 and H1 were differentiated by the overexpression of H1 under magnesium depletion. Iron-regulated membrane proteins (IRMPs) were recognized by their overproduction under iron limitation. Plasma samples from 43 CF patients and ten healthy adults were analyzed after preadsorption with lipopolysaccharide (LPS). Within the first year of colonization, only two to six specific plasma antibodies to OM proteins were produced. After a strong increase during the second year, long-lasting levels were seen in the majority of patients. Large variations of the immune response were noted among the patients. The number of specific antibodies to different OM proteins correlated with the severity of the course of lung disease. At maximum 38 immunostained bands were observed. Proteins H and I were the earliest antigens amongst the major OM proteins. During the second year, antibodies directed to protein F became detectable. IRMPs which indicate the growth of P. aeruginosa under iron deprivation were only recognized by plasma samples from chronically colonized CF patients with advanced lung disease.