Two distinct outer membrane serotype subcomplexes of Neisseria meningitidis serogroup A

Combined roles of human IgG subclass, alternative complement pathway activation, and epitope density in the bactericidal activity of antibodies to meningococcal factor h binding protein

Meningococcal vaccines containing factor H binding protein (fHbp) are in clinical development. fHbp binds human fH, which enables the meningococcus to resist complement-mediated bacteriolysis. Previously, we found that chimeric human IgG1 mouse anti-fHbp monoclonal antibodies (MAbs) had human complement-mediated bactericidal activity only if the MAb inhibited fH binding. Since IgG subclasses differ in their ability to activate complement, we investigated the role of human IgG subclasses on antibody functional activity. We constructed chimeric MAbs in which three different murine fHbp-specific binding domains were each paired with human IgG1, IgG2, or IgG3. Against a wild-type group B isolate, all three IgG3 MAbs, irrespective of their ability to inhibit fH binding, had bactericidal activity that was >5-fold higher than the respective IgG1 MAbs, while the IgG2 MAbs had the least activity. Against a mutant with increased fHbp expression, the anti-fHbp MAbs elicited greater C4b deposition (classical pathway) and greater bactericidal activity than against the wild-type strain, and the IgG1 MAbs had similar or greater activity than the respective IgG3 MAbs. The bactericidal activity against both wild-type and mutant strains also was dependent, in part, on activation of the alternative complement pathway. Thus, at lower epitope density in the wild-type strain, the IgG3 anti-fHbp MAbs had the greatest bactericidal activity. At a higher epitope density in the mutant, the IgG1 MAbs had similar or greater bactericidal activity than the IgG3 MAbs, and the activity was less dependent on the inhibition of fH binding than at a lower epitope density.

Clonal and antigenic analysis of serogroup A Neisseria meningitidis with particular reference to epidemiological features of epidemic meningitis in the People's Republic of China

Representative strains of serogroup A Neisseria meningitidis were chosen from all major meningitis epidemics worldwide since 1960 and subjected to analysis for the electrophoretic variation of 15 cytoplasmic allozymes and four outer membrane proteins. The 290 strains defined 84 unique electrophoretic types which were classified in nine subgroups. Tests with monoclonal antibodies specific for conserved pilin epitopes showed that the class I, IIa, and IIb epitopes were uniform within the subgroups. Similarly, the subgroups were uniform for expression of different variable regions of class 1 outer membrane protein, with a few minor exceptions. Many of the bacteria tested were isolated in the People's Republic of China, and the epidemiology of Chinese epidemics of meningococcal meningitis is described. The analysis approaches a global description of epidemic meningitis caused by serogroup A meningococci in the past 30 years.