FIG. 5.

(A) Increased alternative pathway activation on F62 and mutants in an F62 background. Factor Bb binding to F62 PorMS11 and its LOS mutants was measured by whole-cell ELISA using anti-factor Bb MAb. As controls in this experiment, we used the corresponding LOS mutants in the background of MS11 that contained its native (MS11) Por and wild-type strain F62. Bacteria were incubated with NHS at a final concentration of 10% (vol/vol). (B) Resistance of strains to killing by factor B-depleted serum. F62, F62 PorMS11, F62 PorMS11 lgtE, and F62 PorMS11 lgtF were incubated with factor B-depleted serum (2.5% [vol/vol]), and bactericidal assays were performed (hatched bars). Factor B-depleted serum reconstituted with physiological amounts of factor B was used as a control (solid black bars). The survival of F62 PorMS11 lgtF was significantly lower than those of F62 PorMS11 and F62 PorMS11 lgtE (P ≤ 0.05).