HUMORAL IMMUNE-RESPONSE TO CLASS-1 OUTER-MEMBRANE PROTEIN DURING THE COURSE OF MENINGOCOCCAL DISEASE

We have determined the amounts of specific anti-class 1 outer membrane protein antibodies in sera from 25 patients during the course of syst emic meningococcal disease, using purified class 1 protein as the sens itizing antigen in an enzyme-linked immunosorbent assay. The class 1 p rotein was obtained from a variant of strain 44/76 (B:15:P1.7,16) lack ing class 3 and class 4 outer membrane proteins. Specific anti-class 1 (serosubtype P1.7,16) outer membrane protein immunoglobulin G (IgG) a ntibody levels increased significantly in 12 patients (12 of 25; 48%), regardless of the serotype of the infecting strain, indicating that t he antibodies reacted in part with epitopes not determined by the mono clonal antibodies used for serotyping. Most patients had low levels of anti-class 1 IgG antibodies during the acute illness. The antibody le vels peaked during the second week of disease and returned to near bas eline levels in sera collected 6 weeks to 12 months after the onset of the disease. The majority of the specific anti-class 1 IgG antibodies bound to surface-exposed epitopes on whole bacteria and belonged to t he IgG1 and IgG3 subclasses. Anti-class 1 IgA and IgM antibodies were not detected in any of the patient sera. Prior to disease, seven patie nts had been immunized with a meningococcal outer membrane vesicle vac cine developed from strain 44/76 (P1.7,16). None of these patients was infected with meningococcal strains containing class 1 protein homolo gous or partly homologous to that of the vaccine strain, indicating se rosubtype-specific protection. The highest anti-class I IgG antibody p eak levels were seen in immunized patients infected with strains of he terologous serotype, suggesting an anamnestic response. However, these patients were not protected from meningococcal disease after immuniza tion.