To estimate the extent of meningococcal carriage in the Norwegian population and to investigate the relationship of several characteristics of the population to the carrier state, 1,500 individuals living in rural and small-town areas near Oslo were selected at random from the Norwegian National Population Registry. These persons were asked to complete a questionnaire and to volunteer for a bacteriological tonsillopharyngeal swab sampling. Sixty-three percent of the selected persons participated in the survey. Ninety-one (9.6%) of the volunteers harbored Neisseria meningitidis. The isolates were serogrouped, serotyped, tested for antibiotic resistance, and analyzed by multilocus enzyme electrophoresis. Eight (8.8%) of the 91 isolates represented clones of the two clone complexes that have been responsible for most of the systemic meningococcal disease in Norway in the 1980s. Age between 15 and 24, male sex, and active and passive smoking were found to be independently associated with meningococcal carriage in logistic regression analyses. Working outside the home and having an occupation in transportation or industry also increased the risk for meningococcal carriage in individuals older than 17, when corrections for gender and smoking were made. Assuming that our sample is representative of the Norwegian population, we estimated that about 40,000 individuals in Norway are asymptomatic carriers of isolates with epidemic potential. Thus, carriage eradication among close contacts of persons with systemic disease is unlikely to have a significant impact on the overall epidemiological situation.

The antibody kinetics in sera from 27 adults after three doses of the Norwegian group B meningococcal outer membrane vesicle (OMV) vaccine was studied. The vaccinees received the third dose 4 to 5 years after the first two. Antibody responses against outer membrane proteins (OMPs) and lipopolysaccharides were studied by enzyme-linked immunosorbent assay and immunoblotting and with serum bactericidal assays (SBA) with three variants of the vaccine strain, 44/76. Six weeks after the second injection, the geometric mean (GM) of the levels of immunoglobulin G (IgG) against OMVs was about sevenfold higher than that of prevaccination levels, and 74% of the vaccinees developed a greater-than-twofold rise in SBA titer. After 6 months, the GM of IgG levels declined to about threefold higher, and after 4 to 5 years it declined to about twofold higher, than that before vaccination. The third dose induced a rapid increase in SBA titers in 96% of the vaccinees, and the GM of levels of IgG against OMVs rose to about 14-fold the prevaccination level. One year later, the IgG antibody levels had dropped to 4.6-fold the prevaccination level, but 88% of the vaccinees still showed bactericidal activity. The response after the two first doses was higher in individuals with prevaccination antibodies, but no such effect was found after three doses. The use of defined mutants in SBA and linear multiple regression analyses indicated that among the major OMPs, antibodies to the Opc and class 1 proteins made the most important single contributions to the bactericidal activity against the vaccine strain, but it also demonstrated the importance of antibodies against other antigens. After three doses, 68% of the vaccinees showed a significant SBA response against a strain lacking both the Opc and the class 1 proteins. Three doses converted almost all subjects to SBA responders and gave higher antibody levels and relatively less serosubtype-specific bactericidal activity than did two doses, probably indicating a broader cross-protection against heterologous strains.

Summary.Typing of meningococci with a panel of serotype and subtype specific monoclonal antibodies (MAbs) was compared in co-agglutination, dot-blotting and ELISA tests. Twenty reference strains, 50 case isolates and 133 throat isolates from healthy carriers were studied. The typing results with dot-blotting and ELISA were identical, whereas co-agglutination gave different results for three case and 24 carrier strains. The distribution of serotypes and subtypes among the strains is reported. The combination of the subtypes P1.l and P1.15 in a serotype 15 patient strain was observed. With one case strain and 15 carrier strains, neither serotype nor subtype could be determined. Non-typable and non-subtypable isolates were further characterised by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Coagglutination is useful for typing small numbers of strains with a few MAbs, but less suitable for large-scale typing than the other two methods. Dot-blotting needs less expensive equipment, smaller volumes of antibodies and fewer manipulations than ELISA.

The 5C protein is expressed by the strain of Neisseria meningitidis (44/76) used for production of the Norwegian meningococcal group B outer membrane vesicle vaccine and is included in the final formulation of this vaccine. The immunoglobulin G antibody response to 5C stimulated by vaccination, systemic meningococcal disease, and carriage was measured using ELISAs with synthetic liposomes as antigen and by immunoblotting. Increased levels of IgG were found in paired sera from all three groups. The antibodies were bactericidal to meningococci of serogroups A and B that expressed large amounts of 5C but not to meningococci expressing smaller amounts. There was a linear correlation between bactericidal titer and units of IgG to 5C.

The antibody response of 30 volunteers vaccinated with a complex of group B polysaccharide and outer membrane vesicles (OMV) from serotype 2a Neisseria meningitidis and of 3 individuals who received a placebo vaccine was determined by immunoblotting. OMV were separated by sodium dodecyl sulfate-gel electrophoresis and electrotransferred to nitrocellulose filters. Binding of immunoglobulin G (IgG), IgA, and IgM antibodies in the human sera to OMV components was detected with class-specific peroxidase-conjugated antibodies. The immunoblotting results were also related to the bactericidal activity of the sera and the meningococcal carrier status of the volunteers. Before vaccination weakly reactive bands in the molecular weight range of 140,000 to 10,000 were observed on the blots. Sera from carriers showed more marked bands. Individual patterns of increased reactivity were seen 6 weeks after vaccination. The main immunoreactive components of OMV corresponded to a molecular weight of 43,000 (class 1 protein), 30,000 (class 5 proteins), and 22,000. IgG antibodies in postvaccination sera of high bactericidal titers showed distinct binding to the 43,000-molecular-weight antigen. Meningococcal carriers had antibodies against an antigen of 22,000 molecular weight; in polyacrylamide gels this component did not stain with Coomassie brilliant blue or silver. The marked binding of IgG antibodies to the class 5 proteins decreased considerably between weeks 6 and 25 after vaccination. Periodate oxidation of OMV abolished the binding of IgG antibodies to the class 5 proteins, whereas the antigenicity of the 43,000-molecular-weight (class 1 protein) and 22,000-molecular-weight antigens was unaffected. 571 on July 31, 2020 by guest http://iai.asm.org/ Downloaded from and variation among Neisseriai meningitidis lipopolysaccharides.