Fig. 3.

Complement resistance mechanisms of B. pertussis. B. pertussis has evolved several strategies to evade complement activation. a BrkA, an autotransporter of B. pertussis, has been shown to be involved in complement evasion. The exact mechanism of how BrkA inhibits complement activation remains unknown. b B. pertussis binds C1-inh to the bacterial surface which increased resistance to complement-mediated killing. The Vag8 protein of B. pertussis was identified as the C1-inh binding factor. c B. pertussis binds C4BP via its surface protein FHA and possibly via one or more other receptors. Strains deficient in FHA were still able to bind C4BP, although strongly reduced. d B. pertussis isolates recruit host complement regulators that are part of the fH family such as complement CFH, factor H-like 1 (CFHL), and factor H-related (CFHR) proteins by expressing one or more receptors that have not yet been identified