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Original article
Card9 mediates susceptibility to intestinal pathogens through microbiota modulation and control of bacterial virulence
  1. Bruno Lamas1,2,3,4,5,
  2. Marie-Laure Michel5,
  3. Nadine Waldschmitt6,7,
  4. Hang-Phuong Pham8,
  5. Vassiliki Zacharioudaki6,7,
  6. Louise Dupraz5,
  7. Myriam Delacre6,7,
  8. Jane M Natividad5,
  9. Gregory Da Costa5,
  10. Julien Planchais5,
  11. Bruno Sovran5,
  12. Chantal Bridonneau5,
  13. Adrien Six9,
  14. Philippe Langella5,
  15. Mathias L Richard5,
  16. Mathias Chamaillard6,7,
  17. Harry Sokol1,2,3,4,5,10
  1. 1 Sorbonne University – Université Pierre et Marie Curie (UPMC), Paris, France
  2. 2 Avenir Team Gut Microbiota and Immunity, Equipe de Recherche Labélisée (ERL) 1157, Institut National de la Santé et de la Recherche Médicale (INSERM), Paris, France
  3. 3 Unité Mixte de Recherche (UMR) 7203, Centre National de Recherche Scientifique (CNRS), Paris, France
  4. 4 Laboratoire de BioMolécules (LBM), Centre Hospitalo-Universitaire (CHU) Saint-Antoine 27 rue de Chaligny, Paris, France
  5. 5 Micalis Institute, Institut National de la Recherche Agronomique (INRA), AgroParisTech, Université Paris-Saclay, Jouy en Josas, France
  6. 6 Center for Infection and Immunity of Lille, Institut Pasteur de Lille, Lille, France
  7. 7 INSERM U1019, Team 11, Equipe FRM, INSERM, Lille, France
  8. 8 ILTOO Pharma, 14 rue des Reculettes, Paris, France
  9. 9 Department of Immunology-Immunopathology-Immunotherapy, Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMRS959, Paris, France
  10. 10 Department of Gastroenterology, Saint Antoine Hospital, Assistance Publique—Hopitaux de Paris, UPMC, Paris, France
  1. Correspondence to Pr Harry Sokol, Gastroenterology Department, Hôpital Saint-Antoine, 184 rue du Faubourg Saint-Antoine, 75571 Paris CEDEX 12, France; harry.sokol{at}


Objective In association with innate and adaptive immunity, the microbiota controls the colonisation resistance against intestinal pathogens. Caspase recruitment domain 9 (CARD9), a key innate immunity gene, is required to shape a normal gut microbiota. Card9 –/– mice are more susceptible to the enteric mouse pathogen Citrobacter rodentium that mimics human infections with enteropathogenic and enterohaemorrhagic Escherichia coli. Here, we examined how CARD9 controls C. rodentium infection susceptibility through microbiota-dependent and microbiota-independent mechanisms.

Design C. rodentium infection was assessed in conventional and germ-free (GF) wild-type (WT) and Card9 –/– mice. To explore the impact of Card9 –/–microbiota in infection susceptibility, GF WT mice were colonised with WT (WT→GF) or Card9 –/– (Card9–/– →GF) microbiota before C. rodentium infection. Microbiota composition was determined by 16S rDNA gene sequencing. Inflammation severity was determined by histology score and lipocalin level. Microbiota–host immune system interactions were assessed by quantitative PCR analysis.

Results CARD9 controls pathogen virulence in a microbiota-independent manner by supporting a specific humoral response. Higher susceptibility to C. rodentium-induced colitis was observed in Card9–/– →GF mice. The microbiota of Card9 –/– mice failed to outcompete the monosaccharide-consuming C. rodentium, worsening the infection severity. A polysaccharide-enriched diet counteracted the ecological advantage of C. rodentium and the defective pathogen-specific antibody response in Card9 –/– mice.

Conclusions CARD9 modulates the susceptibility to intestinal infection by controlling the pathogen virulence in a microbiota-dependent and microbiota-independent manner. Genetic susceptibility to intestinal pathogens can be overridden by diet intervention that restores humoural immunity and a competing microbiota.

  • citrobacter rodentium
  • mono- and polysaccharides
  • IBD
  • germfree mice
  • pathogen-specific antibody
  • microbiota

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  • Contributors BL, MLR, MC and HS conceived and designed the study, analysed the data and wrote the manuscript; BL designed and conducted all experiments, unless otherwise indicated; VZ and MD performed the IgG ELISA; H-PP and AS conducted the bioinformatics studies and analysed the microarray experiments; M-LM, NW, JMN, GDC, JP, LD, BS and CB provided technical help for the in vivo experiments; BL, MLR, MLM, NW, PL, MC and HS discussed the experiments and results.

  • Funding This work was funded by ANR-13-BSV3-0014-01.

  • Competing interests None declared.

  • Patient consent This study does not involve human subjects.

  • Provenance and peer review Not commissioned; externally peer reviewed.