Human antibody responses after vaccination with the Norwegian group B meningococcal outer membrane vesicle vaccine: results from ELISA studies.

Antibody responses after vaccination with three different formulations of a new meningococcal group B outer membrane vesicle (OMV) vaccine have been studied with the ELISA technique using four different antigens. Sera from about 1200 vaccinees participating in steps 1, 2, 3 and 6 of the phase II clinical trials in Norway were analysed. The effects of non-covalently complexing the OMV antigen to group C polysaccharide (C-PS) and of adsorbing OMV (with and without C-PS) to aluminium hydroxide (AH) were studied. All three vaccine formulations were highly immunogenic in humans. Adsorption of the vaccine to AH had a relatively small effect on the immune response, but the results indicated that the booster response was stronger with the adsorbed than with the unadsorbed vaccines. Some increase in the immune response against OMV was also observed by non-covalent complexing OMV with C-PS, particularly after the second dose. In most of the vaccinees the antibody levels were significantly reduced 6 to 12 months after vaccination. Adsorption of the vaccine to AH had no effect on the antibody response against C-PS. Comparison with bactericidal activity of the same sera was done. A highly significant correlation was observed between the bactericidal titres and the levels of IgG antibodies against OMV and class 5C protein, whereas the correlation between antibody levels against lipopolysaccharide and the bactericidal activity was poor.