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Benoit-Joseph LAVENTIE

Paris

En résumé

I'm now a post doctoral researcher in the Division of Microbiology of the Biozentrum (Basel, Swiss) in the Urs Jenal group. I'm working on c-di-GMP signaling in Pseudomonas aeruginosa.

Mes compétences :
Cell biology
Molecular biology
Microbiology

Entreprises

  • Biozentrum - Post Doctoral Fellow

    Paris 2011 - maintenant I'm now a post doctoral researcher in the Division of Microbiology of the Biozentrum (Basel, Swiss) in the Urs Jenal group. I'm working on c-di-GMP signaling in Pseudomonas aeruginosa.
  • University of Strasbourg - Teaching assitant

    2007 - 2011 In brief, I teached to student in Bach. of Biology during 4 years (>250h), in the field of animal biology, and in a lesser extent of bioinformatics.
    I also followed a training course of pedagogy (180h).


    Discipline: Animal Biology, module of phylogeny and comparative anatomy of Metazoans, to students in 2nd year Bachelor of Biology. Tutorial classes and Practical work. Responsible for teaching: Sylvie RAISON (raison@inci-cnrs.unistra.fr +33 3 88 45 66 84) ; Head of Discipline: Jean-Marc Reichhart (total teachings = 238h)

    Content of teaching: The phylogenetic classification of Metazoa. Comparative and functional anatomy of major taxa, the advent of the diploblastic and triploblastic state; radial and bilateral symmetry, segmentation, coelom and metamerism; tagmatisation; commonalities and diversity of Porifera, Cnidaria, Helminths, Annelida, Mollusks and Arthropoda; osteology of Chordata. Dissections.

    Module of Bioinformatics, to students in Master degree. Tutorial classes (4h/year = 16h)
  • University of Strasbourg - PhD student

    2007 - 2011 During my thesis, I developed my scientific and organizational skills.
    I worked in the field of bacteriology, on Staphylococcus aureus toxins. My work was both about fundamental knowledge of mode of action of leukotoxins, and development of new anti-toxin molecules, such as dedicated synthetic molecules and engineered heavy chain only antibodies.
    I also learned about team work, especially managing a technician and master degree students, managing deadlines, writing funding applications, and deal with long term project (4 years) in collaboration with international partners. I also teach Bachelor of Biology students during 4 years as teaching assistant.


    PhD THESIS ABSTRACT
    TITLE
    Study of early mechanisms of the Panton-Valentine leucocidin and development of inhibitors versus Staphylococcus aureus leukotoxins
    INTRODUCTION
    Leucotoxins are major virulence factors secreted by the bacteria Staphylococcus aureus. Panton-Valentine leucocidin (PVL), ?-hemolysins, ?-toxin and LukE/LukD are involved in human dermonecrotic diseases and sepsis. PVL is associated with current outbreaks of community-associated methicillin-resistant strains. PVL is directly implicated in the pathophysiology of necrotizing pneumonia, targeting young and healthy patient, and quickly evolving to death in 70% of cases. These pore forming toxins are formed by the association of 2 ?-stranded proteins (class S and class F), apart the mono-partite ?-toxin. Bi-partite leucotoxins oligomerize into hetero-octamers on leukocytes membranes, leading to cell activation and degranulation. Then they reconfigure into a divalent cation selective transmembrane pore, and finally cause cell lysis.
    EARLY EVENTS IN LEUCOTOXINS ACTION: BINDING AND SIGNALISATION
    We first aimed to uncover PVL binding mechanism and particularly its binding domain. The class S compound of PVL, LukS-PV, is known to ensure cell targeting and have the greater affinity for neutrophils membranes. Alanine-scanning mutagenesis (19 mutants) allowed the characterization a cluster of amino acids localized on two loops of the “Rim” domain essential for LukS-PV binding. This domain is only conserved with HlgC (class S protein of ?-hemolysin), that is known to share the same receptor on neutrophils. We also aimed to characterize the pathways involved in intracellular Ca2+ concentration increase following leucotoxin addition onto neutrophils. Pharmacological targeting of calcium channels using Ryanodine, Dantrolene and 2-APB showed that IP3 receptors and Store Operated Channels (SOCs) were involved. Intracellular Ca2+ concentration increase lead to neutrophils dégranulation, which release among other 2 Chromogranin A-derived peptides: Catestatin and Chromofungin. These 2 antimicrobial peptides activate by themselves neutrophils, by inducing calcium entry throw Calmodulin regulation by iPLA2, and probably regulate other immune cells. These results illustrate that leucotoxins have complex direct and indirect impacts on immune system, that their mode of action is much more than simply forming pores.
    DEVELOPMENT AND CHARACTERIZATION OF LEUKOTOXIN INHIBITORS
    We mainly studied the inhibitory properties of 2 class of molecules: para-sulfonato-calix[n]arenes (SCn) and original recombinant antibodies derivatives. SCn have IC50 values between 6–22 µM for neutrophil lysis inhibition and between 2–50 µM for cell activation inhibition, depending on the leucotoxin and the SCn. They form 1:1 complex with class S proteins of all leucotoxins, which prevent further binding to cell membrane. The inhibitory properties of SCn were also observed in vivo in a toxin-induced rabbit endophthalmitis model. Antibodies were engineered against both components of PVL, and also prevent binding to cell membranes, and thus pore formation. The same in vivo model showed that antibodies inhibit inflammatory reactions and tissue destruction. We also demonstrate the superior efficacy of a tetravalent bi-specific HCAb. These results show the therapeutic potential of SCn and antibodies and might represent new therapeutic drugs to figh

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