Neisseria adhesin A (NadA) is one of the antigens of Bexsero, the recently 
licensed multicomponent vaccine against serogroup B Neisseria meningitidis 
(MenB). NadA belongs to the class of oligomeric coiled-coil adhesins and is able 
to mediate adhesion and invasion of human epithelial cells. As a vaccine 
antigen, NadA has been shown to induce high levels of bactericidal antibodies; 
however, the domains important for protective response are still unknown. In 
order to further investigate its immunogenic properties, we have characterized 
the murine IgG1 mAb (6E3) that was able to recognize the 2 main antigenic 
variants of NadA on the surface of MenB strains. The epitope targeted by mAb 6E3 
was mapped by hydrogen-deuterium exchange mass spectrometry and shown to be 
located on the coiled-coil stalk region of NadA (aa 206-249). Although no serum 
bactericidal activity was observed for murine IgG1 mAb 6E3, functional activity 
was restored when using chimeric antibodies in which the variable regions of the 
murine mAb 6E3 were fused to human IgG3 constant regions, thus confirming the 
protective nature of the mAb 6E3 epitope. The use of chimeric antibody molecules 
will enable future investigations of complement-mediated antibody functionality 
independently of the Fc-mediated differences in complement activation.