An enzyme-linked immunosorbent assay (ELISA) has been developed to measure antibodies against pneumococcal polysaccharides of the IgA, IgG and IgM isotypes. Antibodies against pneumococcal polysaccharide types 1, 3, 6A, 8 and 9N were measured by ELISA and radioimmunoassay. Similar antibody responses were observed when comparing both assays. The study included 39 persons at high risk of developing pneumococcal infection and 13 healthy adults. Within 1 month after immunization IgM was the principle isotype. After 1 month, IgG was the principle isotype. Very low levels of IgA were detected in the post-immunization serum. The ELISA procedure described can be used to study the immune response to pneumococcal vaccines.
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