Exploiting chimeric human antibodies to characterize a protective epitope ofNeisseriaadhesin A, one of the Bexsero vaccine components

Abstract

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.

NadA3 Structures Reveal Undecad Coiled Coils and LOX1 Binding Regions Competed by Meningococcus B Vaccine-Elicited Human Antibodies

“…The NadA5 crystal structure included only residues 24 to 137, and no structural information was available for the C-terminal region, including the predicted coiled coil and the highly conserved membrane anchor domain. The NadA5 crystal structure was used as a template to generate a homology model of NadA3, which has been used to aid interpretation of epitope mapping studies ( 30 – 32 ). Recently, a panel of 18 human monoclonal antibodies (humAbs) against NadA were isolated from human subjects vaccinated with 4CMenB ( 32 ).…”

MEMHDX: an interactive tool to expedite the statistical validation and visualization of large HDX-MS datasets

“…The use of improved HDX-MS workflows enables the structural analysis of larger protein systems such as antigen-antibody complexes (> 180 kDa) or integral membrane proteins, in a more routine way (Bertoldi et al , 2016; Chung et al , 2011; Faleri et al , 2014; Malito et al , 2014; Malito et al , 2013). The characterization of such systems results in very complex HDX-MS datasets, for which specific non-commercial analytical software (e.g.…”

Molecular Signatures of Immunity and Immunogenicity in Infection and Vaccination

“…We used HDX coupled to MS to allow the mapping of conformational epitopes ( 21 – 27 ). The approach was also compared with the most sophisticated and available approaches such as protein chip ( 26 , 27 ), phage display ( 21 , 26 , 27 ), X-ray ( 21 ), and cryo-EM ( 24 , 25 ). Modern HDX–MS is more straightforward, rapid, and routine than in the past.…”

“…The approach has sufficient resolution to recognize fHbp overlapping epitopes with different functional properties ( 22 ). It was also successfully applied to map epitopes from NadA ( 23 , 26 ) and NHBA ( 27 ), the two other protective epitopes of the vaccine against group B meningococcus, Bexsero. Hybrid approaches making use of HDX–MS and electron microscopy also evidenced the power of HDX–MS to map viral antigen epitopes of CMV gH–gL complex.…”