Human IgG subclass responses in relation to serum bactericidal and opsonicactivities after immunization with three doses of the Norwegian serogroup B meningococcal outer membrane vesicle vaccine

Ten adult volunteers, with low prevaccination levels of serum IgG antibodie s against meningococcal antigens (< 1 mu g ml(-1)), received three doses of the Norwegian group B meningococcal outer membrane vesicle (OMV) vaccine i ntramuscularly at weeks 1). 6 and 46. Anti-OMV IgG subclass responses were measured and compared with serum bactericidal activity (SBA) and opsonic ac tivity against the vaccine strain 44/76. All vaccinees showed an IgG1 antib ody response after each vaccine dose. The vaccine-induced median serum IgG1 antibody levels were 16, 17 and 18 mu g ml(-1) 2-6 weeks after the first, second and third dose. respectively. Three vaccinees showed a weak IgG3 res ponse after the first dose, whereas 8 and 9 showed a response after the sec ond (median = 10 mu g ml(-1)) and third dose (median = 10 mu g ml(-1)), res pectively. Low levels of anti-OMV IgG2 antibodies were found, whilst specif ic IgG4 antibodies were only detected for one vaccinee. The vaccine induced at least a fourfold increase in SEA titre in 8 vaccinees after the first d ose, in 9 vaccinees after 2 doses and in all vaccinees after 3 doses. A pos itive correlation was found between IgG1 subclass antibody levels and SEA ( r = 0.62, P < 0.0001). Elevated opsonophagocytic activity. measured as resp iratory burst (RB), was observed in all vaccinees after one vaccine dose an d usually increased after 2 and 3 doses. A strong positive correlation was Found between IgG1 antibody levels and RE (r = 0.76, P < 0.0001). In conclu sion, we have shown that systemic meningococcal OMV vaccination in adult va ccinees mainly induced IgG1 antibodies which correlated with bactericidal a nd opsonic activity, but also a considerable amount of IgG3 antibodies, whi ch, in contrast to the IgG1 response. was induced only after 2 or 3 vaccine doses and declined more rapidly. (C) 1999 Elsevier Science Ltd. All lights reserved.