FIGURE 5.

Fusion proteins increase complement deposition on the bacterial surface. Flow cytometry was used to measure C3d, iC3b, and MAC binding at the surface of M. catarrhalis. (A–C) FH6-7/IgG and serum were added simultaneously to bacteria. Bacteria were incubated with 5% OmCI-treated serum for 30 min for C3 deposition, or 10% NHS for 20 min for MAC deposition. Heat-inactivated serum was used as a negative control of complement activation. (D–F) C4BP1-2/IgM and serum were added simultaneously to bacteria. (G–I) Bacteria were pre-incubated with C4BP1-2/IgM before addition of serum. Mean (±SD) from three (A–F) or four (G–I) independent experiments are shown. Statistical significance of differences was calculated using one-way ANOVA with Dunnett’s post-test; *p < 0.05; **p < 0.01.