The Streptococcus agalactiae complement interfering protein combines multiple complement‐inhibitory mechanisms by interacting with both C4 and C3 ligands

What is it about?

In this work we have investigated the role of CIP, a small secreted protein from Group B Streptococcus. These bacteria colonize pregnant women and cause severe infections in neonates. CIP was previously studied for its ability to inhibit the Classical and Lectin Complement Pathways, via its interaction with the C4b Complement component. The present study was aimed at functionally and biochemically characterizing the interaction between CIP and C3, C3b and C3d Complement effectors. We investigated the possible region of CIP involved in C3d binding and detected common aminoacidic patterns with other bacterial C3d-binding proteins. Moreover, we characterized CIP ability to interfere with the interaction between C3d and its CR2/CD21 receptor on B cell surface and therefore to modulate B cell activation. In this respect, our study could represent a valuable contribution to both the characterization of GBS Complement evasion mechanisms and to the development of therapeutics against debilitating autoimmune diseases linked to overactivation of autoreactive B cells.

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