SERUM IGG RESPONSE TO BURKHOLDERIA-CEPACIA OUTER-MEMBRANE ANTIGENS INCYSTIC-FIBROSIS - ASSESSMENT OF CROSS-REACTIVITY WITH PSEUDOMONAS-AERUGINOSA

Burkholderia cepacia (Pseudomonas cepacia) is now recognised as an imp ortant pathogen in cystic fibrosis patients, and several reports have suggested that sputum-culture-proven colonisation occurs despite the p resence of specific antibody. in an attempt to establish the use of an tibody studies as diagnostic and prognostic indicators of B. cepacia i nfection, we have examined the IgG response to B. cepacia outer membra ne proteins and lipopolysaccharide in patients also colonised with P. aeruginosa. The B. cepacia strains were grown in a modified iron-deple ted chemically defined medium and outer membrane components examined b y SDS-PAGE and immunoblotting. IgG antibodies were detected against B. cepacia outer membrane antigens, which were not diminished by extensi ve preadsorption with P. aeruginosa. The response to B. cepacia O-anti gen could be readily removed by adsorption of serum either with B. cep acia whole cells or purified LPS, whereas we were unable to adsorb ant i-outer membrane protein antibodies using B. cepacia whole cells. The inability to adsorb anti-outer membrane protein antibodies using B. ce pacia whole cells maybe due to non-exposed surface epitopes. Several B . cepacia sputum-culture negative patients colonised with P. aeruginos a had antibodies directed against B. cepacia outer membrane protein. T his study suggests that there is a specific anti-B. cepacia LPS IgG re sponse, which is not due to antibodies cross-reactive with P. aerugino sa. Our studies indicate that much of the B. cepacia anti-outer membra ne protein response is specific and not attributable to reactivity aga inst co-migrating LPS.