Immunogenicity of meningococcal antigens as detected in patient sera

The immunogenicity of meningococcal surface antigens was tested in acute- and convalescent-phase sera from patients with meningococcal diseases by enzyme-linked immunosorbent assay and gel immunoradioassay. In gel immunoradioassay, the antigens are separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis before testing their antibody-binding capacity. Both 125I-labeled protein A and 125I-labeled anti-human immunoglobulin G were used to detect antibody binding. It appeared that the variable, low-molecular-weight, heat-modifiable major outer membrane proteins (molecular weights, 25,000 to 32,000) induced strong, strain-specific immunoglobulin G antibody responses. In addition, pili induced strong, cross-reactive antibody responses that could be detected with 125I-labeled protein A, but not with 125I-labeled anti-immunoglobulin G. Antibody responses against capsular polysaccharides, lipopolysaccharides, and minor outer membrane proteins could also be detected by gel immunoradioassay. When tested by enzyme-linked immunosorbent assay against outer membrane complexes, patient sera demonstrated a large amount of cross-reactivity against heterologous meningococcal strains.