Human protective response induced by meningococcus B vaccine is mediated by the synergy of multiple bactericidal epitopes

Abstract

4CMenB is the first broad coverage vaccine for the prevention of invasive meningococcal disease caused by serogroup B strains. To gain a comprehensive picture of the antibody response induced upon 4CMenB vaccination and to obtain relevant translational information directly from human studies, we have isolated a panel of human monoclonal antibodies from adult vaccinees. Based on the Ig-gene sequence of the variable region, 37 antigen-specific monoclonal antibodies were identified and produced as recombinant Fab fragments, and a subset also produced as full length recombinant IgG1 and functionally characterized. We found that the monoclonal antibodies were cross-reactive against different antigen variants and recognized multiple epitopes on each of the antigens. Interestingly, synergy between antibodies targeting different epitopes enhanced the potency of the bactericidal response. This work represents the first extensive characterization of monoclonal antibodies generated in humans upon 4CMenB immunization and contributes to further unraveling the immunological and functional properties of the vaccine antigens. Moreover, understanding the mechanistic nature of protection induced by vaccination paves the way to more rational vaccine design and implementation.

Cocrystal structure of meningococcal factor H binding protein variant 3 reveals a new crossprotective epitope recognized by human mAb 1E6

“…Another possible explanation is species-specific differences in C1q engagement by 1E6. Our results are consistent with prior studies with anti-fHbp mAbs (murine or human), where human complement-mediated bactericidal activity was observed only if the mAb blocked fH-binding or was used in combination with other mAbs (29, 30, 41). Previous studies demonstrated that the quantity of fHbp present on the bacterial surface varies between isolates and in the strains used, MC58, M08-0240104, and UK320 the concentration of fHbp was determined to be 2900 (fHbp v1), 9390 (fHbp v2), and 1111(fHbp v3) molecules for cells, respectively (57).…”

“…Giuliani et al (41) restricted the epitope localization of 1 crossreactive anti-fHbp mAb 1G3 to short fragments of fHbp v1 by hydrogen-deuterium exchange–MS, whereas López-Sagaseta et al (18) were able to fully characterize at high resolution, by X-ray crystallography, the first human antibody, the 1A12, identifying the epitope on fHbp v1. Fab 1A12 targets exclusively the C-terminal β-barrel, whereas the Fab 1E6 mainly binds the N-terminal region on the opposite side compared to the binding site for hfH ( Fig.…”

“…To identify the regions of fHbp where the binding site is localized, we used a protein microarray developed in house that contains the full length of fHbp v1, v2, and v3 and several overlapping fragments covering the entire fHbp variants sequences (41). Genes were expressed in E. coli as either glutathione S -transferase – or His-tagged fusions or thioredoxin fusions purified from the cytoplasmic fraction as soluble forms, and then the recombinant antigens were spotted on nitrocellulose-coated slides.…”

“…Human mAbs against fHbp, Neisserial Heparin Binding Antigen, and Neisseria adhesin A were identified (41). The resulting panel of 10 anti-fHbp antibody fragments (Fabs) was analyzed by 2 different research groups, and both teams found 2 anti-fHbp antibodies (1A12 and 1G3) to be crossreactive with the 3 main fHbp variants (41, 42).…”

“…Human mAbs against fHbp, Neisserial Heparin Binding Antigen, and Neisseria adhesin A were identified (41). The resulting panel of 10 anti-fHbp antibody fragments (Fabs) was analyzed by 2 different research groups, and both teams found 2 anti-fHbp antibodies (1A12 and 1G3) to be crossreactive with the 3 main fHbp variants (41, 42). Moreover, the crystal structure of one of these (1A12) in complex with fHbp v1 was determined, revealing a conserved epitope localized exclusively on the C-terminal β-barrel (18, 41).…”