An enzyme-linked immunosorbent assay suitable for the routine estimation of specific immunoglobulin G responses to polyvalent pneumococcal polysaccharide vaccine in humans.

Antibodies to pneumococcal antigens have routinely been measured by radioimmunoassay (RIA). An enzyme-linked immunosorbent assay (ELISA) is proposed which is simpler and less expensive than RIA. The ELISA was used in a study involving a group of splenectomised patients and controls, to estimate the immunoglobulin G (IgG) response to 5 serotypic antigens (2, 7F, 9N, 14 and 23F) after immunisation with polyvalent pneumococcal polysaccharide vaccine. The 5 serotypic antigens were selected for their low optimum binding concentration and because they represented a range of clinical isolation rates in Western Australia (frequent, medium and rare). No significant difference could be found between the mean-fold increases of the 2 groups using Student's t-test. However, 6 out of 34 splenectomised patients failed to respond to any of the 5 serotypes, whereas no individual in the control group failed to yield a significant response to at least one serotype.