So far my work has focused on deciphering the mechanisms that bacteria use to divert elimination by the innate immune system. My work has led to the discovery that the prominent pathogen Staphylococcus aureus secretes a number of proteins that block critical steps in the complement cascade. As a PhD student in microbiology, I discovered a highly unique bacterial complement inhibitor (SCIN) that blocks a key enzyme of the complement cascade: the C3 convertase (Nature Immunology, 2005). In 2007, I obtained a Veni-grant for the biochemical characterization of SCIN. In close collaboration with Prof. Piet Gros, I managed to resolve the structure of SCIN in complex with the C3 convertase (Nature Immunology, 2009). This was key to the complement field, since the C3 convertase is highly unstable and its structure could only be revealed thanks to the stabilizing properties of SCIN. Furthermore, we discovered two novel staphylococcal complement inhibitors: Efb and Ecb (Journal of Experimental Medicine, 2007). Since these inhibitors were active against murine complement, I obtained a prestigious EMBO fellowship for an advanced postdoctoral training in the laboratory of Prof. Victor Nizet at the University of San Diego, California. Here I obtained the expertise to genetically manipulate bacteria and study bacterial virulence in small animal models. We demonstrated that complement evasion molecules are important virulence factors in vivo. In november 2009, I started my own research group at the Dept. of Medical Microbiology in Utrecht focusing on the intricate interplay between bacteria and the extracellular part of the immune system (complement, coagulation, neutrophil secretions). In 2010, I received a Vidi-grant allowing me to expand my research group. In 2011, I received the prestigious Eppendorf award for Young European Investigators. Recently, we discovered a novel class of neutrophil serine protease inhibitors evolved by bacteria (manuscript submitted). With the ERC grant I hope to establish a completely new line of research in which I try to use my expertise on complement and microbiology to better understand the molecular mechanisms underlying complement labeling and killing of bacteria.