Quantification of IgM and IgA Anti-Pneumococcal Capsular Polysaccharides by a New ELISA Assay: a Valuable Diagnostic and Prognostic Tool for Common Variable Immunodeficiency

Purpose Existing ways of assessing CVID patients at risk of pulmonary infections are not universally accepted. The need to identify additional prognostic factors allowed us to evaluate the anti-polysaccharide IgA and IgM responses in 125 CVID patients immunized with the 23-valent pneumococcal polysaccharide (PS) vaccine (Pneumovax (R)). Methods We used a new anti-PS23 IgM and IgA ELISA assay, which evaluates a global response to all 23 polysaccharides contained in Pneumovax (R). Results Anti-PS23 IgM and/or IgA antibodies were detectable in a minority of CVID patients. Antibody responses were correlated to B cell subpopulations and serum immunoglobulin concentrations. The non responders had a higher incidence of pneumonia and bronchiectasis and responders had the lowest incidence of respiratory complications. Conclusions This new ELISA assay allows for studying vaccine response in patients on Ig replacement therapy. This test also is an additional method of evaluation of specific antibody responses representing a valuable contribution to identify prognostic marker in CVID patients.