Molecular basis of giant Extracellular Matrix Binding Protein (Embp) mediated Staphylococcus epidermidis adherence to fibronectin and biofilm accumulation on artificial surfaces

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The overall objective of this project is to obtain comprehensive insights into the molecular basis of Embp mediated S. epidermidis biofilm formation and its relevance to bacterial / host interactions during pathogenesis of experimental foreign material associated infections. The objective will be reached by addressing key aspects of Embp dependent S. epidermidis virulence using a variety of experimental approaches, including molecular biological techniques, cell culture systems and establishment of three dimensional model systems of implant associated infections. 1. We will characterize the exact modalities of Embp / FN interactions on a molecular / biochemical level and analyze their role during S. epidermidis binding to surface organized FN. In addition, the importance of dynamic conformational changes during FN fibrillogenesis and consecutive exposure of cryptic epitopes, e.g. FN III12 to 14, will be analyzed.Rational: S. epidermidis binding to FN is of paramount importance for initiation of implant associated infections. Embp proved to be necessary for FN dependent S. epidermidis adherence to implant surfaces. However, the exact molecular determinants of this interaction are currently unclear. Work from our groups demonstrates that Embp employs a so far unknown mode of interaction with FN involving binding to cryptic modules FN III12 to 14. 2. A three dimensional model of implant associated infections will be established and validated. The model will allow for analysis of the temporal and spatial dynamics during Embp dependent S. epidermidis implant colonization, biofilm formation and interactions with host innate immune cells. Rational: Currently assay systems used for analysis of S. epidermidis biofilm formation do not reflect the complex setting of an in vivo infection occurring at the interface between foreign materials and the surrounding tissues consisting of extracellular matrix, and a diverse set of resident cells (e.g. fibroblasts, macrophages). This specific topography, which essentially applies for most S. epidermidis device related infections (e.g. associated with prosthetic joints, CSF shunts, artificial heart valves) could have dramatic impact on biofilm development and dynamic interactions of S. epidermidis with host cells.Collectively, analysis of these objectives will not only provide novel insights into general aspects of bacterial pathogenesis and microbe / host interactions, but more specifically address central aspects related to the pathogenesis of S. epidermidis implant infections. Considering the gravity of the clinical problem, the proposed project could provide new starting points for development of novel therapeutic and / or prophylactic approaches that are necessary to combat devastating device related S. epidermidis infections.