Microbes and Host Barriers - Inserm avenir, Team FRM, Univ. Paris Descartes  

  HEADProf. Marc LECUIT, MD PhD / mlecuit@pasteur.fr
  MEMBERSMembers of the G5 : Ms. Corinne BARAN, Dr. Thérèse COUDERC, Dr. Olivier DISSON, Ms. Delphine JUDITH, M. Georgios NIKITAS, M. Nicolas GANGNEUX
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

  Annual Report

A number of viral, bacterial, and protozoan 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.

In 2008, we have developed the first animal model for Chikungunya, a mosquito-borne infection characterized by fever, arthralgia, myalgia, rash, and occasionally encephalitis (Couderc et al. PLoS Pathogens, 2008). We have determined the cell and tissue tropisms of Chikungunya virus, and showed that both in vitro and in vivo, Chikungunya virus 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). In collaboration with colleagues from the Centre Hospitalier Sud-Réunion, we have also demonstrated the possible vertical transmission of Chikungunya virus during delivery (Gérardin et al. PLoS Medicine 2008).

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.

Our lab also hosts the National Reference Centre and WHO collaborating centre for Listeria. 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 blue and Listeria in green. © Disson & Lecuit


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

Gérardin P, Barau G, Michault A, Bintner M, Randrianaivo H, Choker G, Lenglet Y, Touret Y, Bouveret A, Grivard P, Le Roux K, Blanc S, Schuffenecker I, Couderc T, Arenzana-Seisdedos F, Lecuit M*, Robillard PY*, 2008, Multidisciplinary prospective study of mother-to-child chikungunya virus infections on the island of La Réunion PLoS Medicine 5(3): p. e60 PMID: 18351797

Lecuit M., 2007, Human listeriosis and animal models Microbes Infect. 9(10):1216-25 PMID: 17720601

Lecuit M, Sonnenburg JL, Cossart P, Gordon JI, 2007, Functional genomic studies of the intestinal response to a foodborne enteropathogen in a humanized gnotobiotic mouse model J. Biol. Chem.282(20):15065-72 PMID: 17389602

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