1. Arterial wall colonization by bacteria: a critical stage before chaos Guillaume Dumenil Avenir team - INSERM U970 Paris center for cardiovascular research (PARCC) Hôpital Européen Georges Pompidou (HEGP) CEA CHRU CNRS CPU INRA INRIA INSERM INSTITUT PASTEUR IRD

2. Septicemia: when bacteria reach the bloodstream… Gram - Gram + Fungi Aspergillus N. meningitidis S. aureus S. pneumoniae S. pyogenes E. coli Vascular dysfunction leak Coagulation Inflammation Meningitis … . Sepsis in the US: 800 000 deaths/year … and colonize blood vessels P. aeruginosa C. albicans

3. The Neisseria meningitidis model 2- Crossing of the epithelium 3- Proliferation in the blood 5- Proliferation in the cerebrospinal fluid 4- Crossing of the blood-brain barrier Meningitis Septicemia Vessel damage Purpura fulminans 1- Colonization of the Nasopharynx

4. Building relevant septicemia models: major challenges • Blood flow generated mechanical forces • Specific tissue architecture • Species specificity • Microcirculation 10 µm - ECM - Surrounding cells - Microenvironement Flow r F T V D

5. Interaction with the endothelium is mediated by type IV pili Agreggation Fiber PilE Adhesion Type IV pili are involved in all stages of blood vessel colonization Neisseria meningitidis

6. Stage 1: site of adhesion determined by shear stress Pump 500µm Bacteria are targeted to cerebral microcirculation • Adhesion In vitro • Shear stress levels in vivo Intravital imaging Mairey et al. J Exp Med 2006

7. Stage 2: Intense cross-talk between cells and bacteria In absence of plasma membrane reorganization Microcolony disruption Live imaging Biofilm-like structure Bacteria Cellular protrusions Bacteria manipulate host cells to resist shear stress Mikaty et al. PLOS Path. 2006

8. Stage 3: Detachment is a highly regulated process Chamot-Rooke Science 2011 Periplasm Inner membraine Posttranslational Modifications of type IV pili Major pilin PptB Top down mass spectrometry Patent pending The PptB enzyme is a possible therapeutic target