Serum antibody responses of wild-type (WT, X symbols) or human fH transgenic (Tg, square symbols) mice immunized with a fHbp vaccine that bound human fH. A, IgG anti-fHbp responses. Titers of individual mice are represented by the respective symbols and the geometric mean titers are indicated by horizontal lines. The symbols for mice immunized with negative control vaccines are titers of serum pools, each from 3-4 mice. B, Serum bactericidal responses measured with human complement against group B strain H44/76. Symbols represent titers of individual mice as in Panel A. Comparing respective IgG GMT of fHbp immunized WT and Tg mice, Study 1, P=0.03; Study 2, P=0.025. Comparing respective SBA GMT of fHbp immunized WT and Tg mice, Study 1, P=0.03; Study 2, P=0.05.