Figure 1.

Phylogenetic tree for FHbp, adapted with permission from Ostergaard et al. N Engl J Med. 2017;377:2349–2362 [76]. The grouping of variants into subfamilies A and B [22] is indicated; an alternative classification scheme involving 3 variant groups [37] is also depicted. Coloured circles indicate FHbp antigens included in MenB-4C [11] and MenB-FHbp [12] as well as strains used to evaluate immune responses to both vaccines in clinical studies [58,75]. For MenB-4C, the indicator strain used to evaluate FHbp-mediated bactericidal immune responses expresses FHbp variant B24 and is thus homologous to the vaccine antigen for FHbp [58]. The 4 primary and 10 additional strains used to measure the immune response to MenB-FHbp express sequence-diverse FHbp variants that are different from the vaccine antigens [9,74]. The scale bar indicates phylogenetic distance using protein sequence. FHbp=factor H binding proteins; hSBA=serum bactericidal antibody assay using human complement; MenB-4C=Bexsero^®, 4CMenB; MenB-FHbp=Trumenba^®, bivalent rLP2086.