Deciphering In Vivo Host Anthrax Interactions

This project addresses the problematic raised in Thematic axis 7, concerning the analysis and evaluation of the risk arising from a NRBC threat, more specifically the biological threat due the consequences of anthrax contamination. It presents a strong dual outcome of the research, both civilian and with specificity for answering defense needs. The bioterrorist anthrax US attack in 2001 has exemplified the life threatening consequences on the health of the civil and military personnel exposed to anthrax spores, and the ensuing economy and societal disruptions. A better understanding of the disease could thus be a means to decrease the health consequences of exposure to anthrax spores and thus impact the costs generated by such bioterrist acts for the society. The initial steps of anthrax infection are still insufficiently understood. A gap of knowledge exist on the precise mechanisms used by B. anthracis to interact, successfully invade and disseminate into the host. A wealth of data has been accumulated in in vitro systems, but their relevance to in vivo conditions of infection is regularly questionned. Translation to in vivo models are severely hampered by a lack of appropriate methods. The proposed project aims at imaging in vivo and in real time the initial steps of anthrax, both cutaneous and inhalational, by combining powerful complementary fluorescence methodologies, biphotonic microscopy and ex vivo 3-D reconstruction on BSL3 B. anthracis infected tissues of mice displaying fluorescent lymphatic and blood vessels, or fluorescent immune cells (such as dendritic cells). Through these imaging technologies combined to histological and ultrastructural analysis, we will visualize and characterize in real time the entry of B. anthracis, the local dynamics of the bacterial differentiation steps (germination and capsule and toxin production) and dynamically define the local subversive effects of the toxins on the local host control mechanisms during an infection; more specifically on the integrity of lymphatic and blood endothelial cells and the dynamics of innate immune cell recruitment. Overall, the combination of these imaging approaches will provide a unique and novel picture of B. anthracis infection. The outcomes of this project include: - a better understanding of the critical initial steps of anthrax, both cutaneous and inhalational - the development of new molecular approaches to the early treatment of B. anthracis infection and vaccination strategies. - the development of novel visualization technologies to follow in real time an infection that could be applied to other pathogens of interest This work should also make it possible to improve the societal and economic countermeasures to be taken in cases of biological terrorist threats.