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

  HEADProf. Marc LECUIT / mlecuit@pasteur.fr
  MEMBERSMembers of the G5 : Ms. Corinne BARAN Dr. Thérèse COUDERC Dr. Olivier DISSON Dr. Chantal DESCHAMPS Ms. Delphine JUDITH M. Giorgos NIKITAS M. Nicolas GANGNEUX M. Florent LAFERRIERE
Members of the National Reference Centre and WHO collaborating centre for Listeria Ms. Martine BELIN M. Alexandre LECLERCQ Ms. Viviane CHENAL-FRANCISQUE M. Thomas CANTINELLI Ms. Hélène DIEYE Ms. Anne MORVAN Dr. Solène GRAYO M. Arnaud BERTEL Ms. Nathalie TESSAUD RITA Dr. Caroline CHARLIER-WOERTHER

  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 last year developed the first animal model to study this infection, and determined the cell and tissue tropisms of Chikungunya virus (CHIKV). We also 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 now developed the first effective preventive and therapeutic approach against CHIKV (Couderc et al. J. Infect. Dis. 2009). In collaboration with the laboratory of Dr. M. Albert, we have also investigated the host response to CHIKV (Schilte et al. J. Exp. Med., 2010). We also 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). To do so, we have characterized two new animal models for human listeriosis, permissive to both InlA and InB interactions with their receptors: the gerbil, a natural host for Listeria, and a new knock-in humanized mouse line that expresses a punctually modified E-cadherin enabled to interact with InlA. This year, 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). We have also continued our investigations on the intestinal phase of listeriosis (Nikitas et al. in preparation), as well as on neurolisteriosis. We have also worked, in collaboration with Prof. C. Poyart, on the pathophysiology of Group B streptococcus-associated neonatal infections (Tazi et al., in preparation).

Our laboratory also hosts the National Reference Centre and WHO collaborating centre for Listeria. This year, we have described a new species of Listeria, L. rocourtiae (Leclercq et al. Int. J. Syst. Evol. Microbiol.), and have also reported the pathogenicity for humans of the ruminant pathogen L. ivanovii (Guillet et al. Emerg. Infect. Dis, 2009). We have also launched a prospective study on human listeriosis, called MONALISA. For details, visit http://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

Scanning electron microscopy picture of the filopod of a Chikungunya virus-infected fibroblast. The image is artificially colorized, and viral particles appear in yellow. © Couderc & Lecuit

Right panel

Immunolabelled section of a gerbil placenta 72 h after intravenous infection with Listeria monocytogenes.E-cadherin appears in red, fetal capillaries in cyan, nuclei in bue and Listeria in green. © Disson & Lecuit


Levraud JP, Disson O, Kissa K, I Bonne, Cossart P, Herbomel P, Lecuit M, 2009, Real-time observation of Listeria-phagocyte interactions in the living zebrafish larva Infect Immun. 77(9):3651-60 . PMID: 19546195

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, 2009, The Listeria transcriptional landscape from saprophytism to virulence Nature 459(7249):950-6. PMID: 19448609

Couderc T, Khandoudi N, Grandadam M, Visse C, Gangneux N, Bagot S, Prost JF, Lecuit M, 2009, Prophylaxis and Therapy for Chikungunya Virus Infection J. Infect. Dis. 200(4):516-23 . PMID: 19572805

Disson O, Grayo S, Huillet E, Nikitas G, Langa-Vives F, Dussurget O, Ragon M, Le Monnier A, Babinet C, Cossart P, Lecuit M, 2008, Conjugated action of two species-specific invasion proteins for fetoplacental listeriosis Nature 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, 2008, A mouse model for Chikungunya infection: young age and inefficient type-I interferon signaling are risk factors for severe disease PLoS Pathog. 4(2): p. e29. PMID: 18282093

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Activity Reports 2009 - Institut Pasteur
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