Fig. 6: Serum IgG responses in mice to the bivalent TbpB composition.

A, B Detection of anti-TbpB IgG in serum of C57BL/6 mice against each immunizing antigen after 1–3 doses of the bivalent (Ngo 48627 + Ngo 41385) TbpB vaccine. Separate ELISAs were performed using 41385 TbpB (A) and 48627 TbpB (B) protein-coated plates to assess the IgG response against each antigen. N = 23 for TbpB vaccinated cohort, N = 6 for adjuvant controls. Bars represent mean, error bars represent standard error. C Cross-reactivity of terminal serum from bivalent TbpB immunized mice against a broad panel of Neisserial TbpB proteins belonging to different clusters. Optical density (OD) values were normalized with Ngo 41385 TbpB and MBP (empty vector) set at 1 and 0, respectively, with any negative values (signal below empty vector) plotted as 0. N = 10 serum samples from mice immunized with bivalent TbpB formulation evaluated. Bars represent mean, error bars represent standard error. Inset, ELISA plate capture control using hTf-HRP binding as a readout to detect folded TbpB. Mean ± standard deviation of three technical replicates. D Human transferrin blocking ability of immune mouse serum. Serum samples from N = 15 mice/group were added to wells coated with 15 different gonococcal TbpBs. hTf-HRP was added to the probe for hTf blocking. OD was normalized to the no serum control for each TbpB-hTf signal. Each dot represents serum from one mouse immunized with either the bivalent TbpB formulation (pink bars, squares) or Addavax only (white bars, circles). ** represents p < 0.01, *** represents p < 0.001, **** represents p < 0.0001. Non-significant differences in panels A and B are not shown. Serum immunogenicity was compared between doses by 2 way ANOVA with Sidak’s multiple comparisons test comparing matched samples. hTf blocking compared with two-way ANOVA with Sidak’s multiple comparisons test comparing normalized OD from sera from bivalent immunized mice versus Addavax immunized mice against each captured TbpB.