Serum IgG and sputum IgA antibody to core lipopolysaccharide antigen from Pseudomonas cepacia in patients with cystic fibrosis.

The immunological response of cystic fibrosis (CF) patients to lipopolysaccharide (LPS) antigens of Pseudomonas cepacia was investigated. Enzyme-linked immunosorbent assays (ELISA) with either P. cepacia whole cells or extracted core LPS from a clinical isolate of P. cepacia as antigen were used to measure serum IgG and sputum IgA anti-P. cepacia antibodies. The ELISA with core LPS distinguished nine CF patients colonised by P. cepacia from nine age- and sex-matched non-colonised CF patients. The rate of increase of anti-P. cepacia IgG antibodies after bacteriologically proven P. cepacia colonisation varied in individual patients: in some patients the first isolation of P. cepacia was preceded or accompanied by a two-to-four-fold rise in anti-P. cepacia LPS IgG titres. Absorption studies and immunoblot analysis of serum from patients colonised with P. cepacia demonstrated that a significant component of the anti-P. cepacia core LPS antibodies was specific for P. cepacia and did not react with the core LPS of P. aeruginosa. Immunoblotting also illustrated that there may be a degree of core heterogeneity between different isolates of P. cepacia. Detection of P. cepacia LPS specific antibodies in serum (IgG) and sputum (IgA) from CF patients is recommended to assist the identification of P. cepacia colonisation in CF patients.