Measurement of immunoglobulin G and M antibodies to type 3 pneumococcal capsular polysaccharide by enzyme-linked immunosorbent assay.

An enzyme-linked immunosorbent assay was developed to measure immunoglobulin G (IgG) and IgM type 3 antipneumococcal capsular polysaccharide antibodies. The use of Fab2 fragments of rabbit antipneumococcal IgG antibody in the antibody-antigen sandwich increased the sensitivity for measuring IgM antibodies and decreased background activity in antigen-free cuvettes. This methodology detected type 3 IgM antibody responses in six of six subjects vaccinated with polyvalent pneumococcal vaccine and detected type 3 IgG antibody responses in three subjects. Results of the enzyme-linked immunosorbent assay and radioimmunoassay procedures were concordant, and postvaccination enzyme-linked immunosorbent assay IgM titers showed a stronger correlation with total radioimmunoassay antibody than did postvaccination ELISA IgG titers.