Immunoglobulin GM and KM allotypes are associated with antibody responses to Pseudomonas aeruginosa antigens in chronically infected cystic fibrosis patients.

Background: Chronic infection with Pseudomonas aeruginosa (P. aeruginosa) is a leading cause of death in patients with cystic fibrosis (CF). Immunobiology of P. aeruginosa infection is complex and not well understood. Chronically infected CF patients generate high levels of antibodies to P. aeruginosa, but this response does not lead to clinical improvement. Therefore, additional studies aimed at identification and understanding of the host factors that influence naturally occurring immune responses to P. aeruginosa are needed. In this investigation, we evaluated the contribution of immunoglobulin GM (γ marker) and KM (κ marker) allotypes to the antibody responses to P. aeruginosa lipopolysaccharide (LPS) O1, O6, O11, and alginate antigens and the broadly-conserved surface polysaccharide expressed by many microbial pathogens, poly-N-acetyl-D-glucosamine (PNAG), in 58 chronically infected CF patients.

Methods: IgG1 markers GM 3 and 17 and IgG2 markers GM 23- and 23+ were determined by a pre-designed TaqMan® genotyping assay. The κ chain determinants KM 1 and 3 were characterized by PCR-RFLP. Antibodies to the LPS O antigens, alginate, and PNAG were measured by an ELISA.

Results: Several significant associations were noted with KM alleles. Particular KM 1/3 genotypes were individually and epistatically (with GM 3/17) associated with the level of IgG antibodies to O1, O11, alginate, and PNAG antigens.

Conclusions: Immunoglobulin GM and KM genotypes influence the magnitude of humoral immunity to LPS O, alginate, and PNAG antigens. These results, if confirmed in a larger study population, will be helpful in devising novel immunotherapeutic approaches against P. aeruginosa.