Microbes and Host Barriers - Inserm avenir U604, Université Paris Descartes, FRM  

  HEADProf. Marc LECUIT / mlecuit@pasteur.fr
  MEMBERSMembers of the G5: Ms. Corinne BARAN Dr. Thérèse COUDERC, PhD Dr. Olivier DISSON, PhD Dr. Chantal DESCHAMPS, PhD Dr. Théodora NIAULT, PhD Dr. Laetitia TRAVIER, PhD Ms. Delphine JUDITH M. Yu-Huan TSAI M. Nicolas GANGNEUX
Members of the National Reference Centre and WHO collaborating centre for Listeria Ms. Martine BELIN M. Alexandre LECLERCQ, deputy head of NRC for Listeria Ms. Viviane CHENAL-FRANCISQUE M. Thomas CANTINELLI Ms. Hélène DIEYE Ms. Anne MORVAN M. Arnaud BERTEL Ms. Nathalie TESSAUD RITA Dr. Caroline CHARLIER-WOERTHER, MD PhD Dr. Benoît CAZENAVE, MD Ms. Irma MALECKAR

  Annual Report

A number of microbial pathogens have in common the ability to actively invade a mucosa and cross the blood-brain barrier (BBB) and materno-fetal barrier (MFB). The objective of our group is the deciphering of the molecular mechanisms underlying microbial targeting and crossing of these host barriers. Building on our expertise on the model microorganism Listeria monocytogenes, which invades the intestinal mucosa and cross the BBB and the MFB, we have broaden our investigations to a series of other microorganisms with a similar tropism, including bacteria such as group B streptococci, and viruses such as enteroviruses, flaviviruses and alphaviruses.

In vivo, ex vivo and in vitro approaches and molecular and cell biology techniques are combined to (i) study at the whole organism, tissue and cell levels microbial targeting and crossing of host barriers, (ii) identify the corresponding microbial and host determinants mediating these effects and (iii) study the host response to infection at the barrier level.

In vivo models of infections are used, in combination with real-time imaging techniques including two-photon and spinning disk confocal microscopy and bioluminescence imaging, for in vivo tracking of fluorescent or bioluminescent microorganisms, respectively. This allows the real time imaging of the actual breaching of host barriers. Magnetic resonance imaging is also used for detecting the ensuing development of parenchymal lesions in the central nervous system and the feto-placental unit in living animals.

We have also set up experimental tools for studying the BBB and the MFB in vitro and ex vivo. In addition to classical mucosal barrier models, primary cell culture techniques that allow reproducing in vitro on microfilters the choroid plexus epithelial barrier and the brain microvascular endothelial barrier at the BBB level, as well as the placental and amniotic barriers at the MFB level are now available for experimental infection in different rodent species. Choroid plexus tissue explants, isolated brain microvessels, placental and amniotic tissue explants as well as intestinal explants can also be cultured and infected ex vivo, as well as infected in a dynamic context better mimicking the in vivo situation (microperfusion of microdissected tissue explants, and artificial fluid flow on cells grown in laminar fluid flow chambers).

By integrating these complementary techniques representative of the emerging “Tissular Microbiology” discipline and molecular and cell biology approaches, we wish to gain a better understanding of the molecular mechanisms underlying microbial translocation across mucosal barriers and microbial access to the central nervous system and the feto-placental unit. This will hopefully lead to the identification of novel medically relevant host-microbial interactions. The identified molecular players might then be exploited for designing new therapeutic approaches aimed at inhibiting microbial access to the central nervous system and the fetus, as well as at transferring molecules of interest across the BBB and the MFB. Overall, our research should also lead to a better comprehension of the basic cell biology of host barriers.

This year, we have continued our investigations on Chikungunya, a mosquito-borne infection characterized by fever, arthralgia, myalgia, rash, and occasionally encephalitis. We had developed the first animal model to study this infection, and determined the cell and tissue tropisms of Chikungunya virus (CHIKV), and showed that CHIKV specifically targets fibroblasts of skeletal muscles, joint capsules, and dermis, and may also disseminate to the central nervous system, where it infects choroid plexuses and the meningeal and ependymal envelopes (Couderc et al. PLoS Pathogens, 2008). We have developed the first effective preventive and therapeutic approach against CHIKV (Couderc et al. J. Infect. Dis. 2009). This year, in collaboration with the laboratory of Dr. M. Albert, we have investigated the host response to CHIKV (Schilte et al. J. Exp. Med., 2010). We currently study the cell biology of CHIKV infection.

Continuing our work on Listeria, we have uncovered the molecular mechanisms by which Listeria targets and crosses the placental barrier. It relies on the conjugated action of InlA and InlB, two listerial surface proteins interacting in a species-specific manner with their respective receptors E-cadherin and Met (Disson et al. Nature, 2008). We have also developed, in collaboration with Dr. JP. Levraut, a novel animal model to study liseriosis, the zebrafish, a genetically amenable and optically accessible small vertebrate in which the septicemic phase of the infection can be readily investigated (Levraut et al., Infect. Immun, 2009). This year, we have continued our investigations on the intestinal phase of listeriosis (Nikitas et al. in preparation), as well as on neurolisteriosis (Disson et al. in preparation). We have also investigated, in collaboration with Prof. C. Poyart, the pathophysiology of Group B streptococcus-associated neonatal infections, and shown the surface protein HvgA mediates Group B streptococcus hypervirulence and meningeal tropism in neonates (Tazi et al., J. Exp. Med, 2010).

Our laboratory also hosts the National Reference Centre and WHO collaborating centre for Listeria. This year, in collaboration with Dr. S. Brisse, PF8, we have performed a worldwide global analysis of Listeria monocytogenesclones (Chenal-Francisque et al. Emerg. Infect. Dis, under revision). We have also performed a national study of antimicrobial resistance of Listeria monocytogenesstrains isolated from humans in France (Morvan et al. Antimicrob Agents Chemother. 2010). Finally, we are continuing our prospective study on human listeriosis, called MONALISA. For details, visithttp://www.pasteur.fr/sante/clre/cadrecnr/listeria-index.html

Keywords: Bacteria, virus, Listeria, chikungunya, Group B streptococcus, intestine, placenta, blood-brain barrier, barriers, pathophysiology, cell biology, molecular biology, imaging


Left panel

Transmission electron microscopy picture of Chikungunya virus particles budding at the surface of an infected cell. © Couderc & Lecuit

Right panel

Immunolabelled section of the brain of a mouse exeprimentally infected with clone ST17 Group B streptococcus. Bacteria (green) infect a brain microvessel (red). © Disson & Lecuit


Tazi A, Disson O, Bellais S, Bouaboud A, Dmytruk N, Dramsi S, Mistou M-Y, Khun H, Mechler C, Tardieux I, Trieu-Cuot P, Lecuit M*, Poyart C*. The surface protein HvgA mediates Group B streptococcus hypervirulence and meningeal tropism in neonates. J Exp Med 2010, 25;207(11):2313-22. PMID: 20956545

Schilte C, Couderc T, Chrétien F, Sourisseau M, Gangneux N, Guivel-Benhassine F, Gruber A, Tschopp J, Higgs S, Michault A, Arenzana-Seisdedos F, Colonna M, Schwartz O, Lecuit M*, Albert M*. Type I IFN controls chikungunya virus via its action on non-hematopoetic cells.. J Exp Med 2010, 15;207(2):429-42. PMID: 20123960

Toledo-Arana A, Dussurget O, Nikitas G, Sesto N, Guet-Revillet H, Balestrino D, Loh E, Gripenland J, Tiensuu T, Vaitkevicius K, Barthelemy M, Vergassola M, Nahori M-A, Soubigou G, Régnault B, Coppée J-Y, Lecuit M, Johansson J, Cossart P. The Listeria transcriptional landscape from saprophytism to virulence. Nature 2009, 459(7249):950-6. PMID: 19448609

Disson O, Grayo S, Huillet E, Nikitas G, Langa-Vives F, Dussurget O, Ragon M, Le Monnier A, Babinet C, Cossart P, Lecuit M. Conjugated action of two species-specific invasion proteins for fetoplacental listeriosis. Nature 2008, 455(7216):1114-8. PMID: 18806773

Couderc T, Chrétien F, Schilte C, Disson O, Brigitte M, Guivel-Benhassine F, Touret Y, Barau G, Prévost MC, Schuffenecker I, Desprès P, Arenzana-Seisdedos F, Michault A, Albert ML, Lecuit M

A mouse model for Chikungunya infection: young age and inefficient type-I interferon signaling are risk factors for severe disease. PLoS Pathog 2008, 4(2): p. e29. PMID: 18282093

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