DEFECTIVE ANTIBODY-MEDIATED OPSONIZATION OF STREPTOCOCCUS-PNEUMONIAE IN HIGH-RISK PATIENTS DETECTED BY FLOW-CYTOMETRY

Invasive pneumococcal infection continues to be a significant cause of morbidity and mortality especially in patients with antibody deficien cies and disorders affecting the reticulo-endothelial system. Current recommendations for prophylaxis in these patients include immunization with 23-valent pneumococcal polysaccharide capsular vaccines. Post-im munization responses are commonly assessed by measuring serum antibody levels. However, there is no defined protective antibody range and th is approach fails to determine the functional capacity of the antibodi es. A simple, reproducible flow cytometric method of assessing the ant ibody-mediated opsonic activity against S. pneumoniae is described. Th is assay detected defective opsonic function in post-immunized at-risk patients who developed invasive pneumococcal infection.