FIG 6.

Human FH enhances survival of FHbp/NspA double-KO mutants of N. meningitidis in infant rat serum. (A) Survival in 60% infant rat serum. Bacteria were incubated in pooled sera from wild-type infant rats, to which was added different concentrations of human FH. Open squares with solid black line, double-KO mutant of R1; open circles with dashed black line, double-KO mutant of S1. The data points represent median value (ranges) of triplicate measurements. The results were replicated in an independent experiment. (B) Binding of recombinant FH domain fragments fused to mouse Fc to FHbp/NspA double-KO mutants by flow cytometry. Solid black line, resistant (R) isolates; dashed black lines, susceptible (S) isolates; gray-filled histogram, bacteria without added recombinant fragment. Left, FH domain 6,7/Fc; right, FH domain 18-20/Fc. Representative data from one assay are shown. The results were replicated in a second experiment.