PhD defense of Caroline PLAZY on 06/03/22


PhD defense of Caroline PLAZY from TIMC TrEE on June, the 3rd, at 1pm:

« Identification of metabolite-mediated immunomodulations:
from identification to application in an infectious context »
 

bullet Jury:

  • Bertrand TOUSSAINT, Professeur des Universités - Praticien Hospitalier, Université Grenoble Alpes, TIMC, Supervisor
  • Eric KIPNIS, Professeur des Universités - Praticien Hospitalier, Université de Lille, Co-supervisor
  • Laetitia AYMERIC, Maîtresse de conférence, Université d'Angers et de Nantes, TENS-INSERM, Reporter
  • Max MAURIN, Professeur des Universités - Praticien Hospitalier, Université Grenoble Alpes, Examiner
  • François FENAILLE, ingénieur HDR, CEA Paris Saclay, Examiner
     

bullet  Keywords:  

Immunomodulation, host/pathogen crosstalk, metabolites

bullet Abstract:

Background and objectives:
During chronic patient’s infection, bacteria will adapt themselves to the pulmonary environment and especially to the immune system by secreting or expressing a multitude of pro / anti-inflammatory molecules. Among them, some metabolites, i.e. immunometabolites, have been described as altering the activation and the polarization of subsequent immune responses. To improve the knowledge on host/microbe crosstalk and to identify new immunometabolites, we have investigated the modulation of the immune system induced by clinical strains of Pseudomonas aeruginosa (Pa) isolated from chronically infected CF patients.
Materiel & Methods:
Thirty two CF patients were included in the study and for each patient 2 isolates were collected 5 years apart. We collected the supernatant of the strains to analyze the modulation of the activation/maturation of dendritic cells (DC) under TLR activation induced by the excreted metabolites. To confirm these results, we evaluated T cell (LT) polarization in vitro in an allogeneic CD-LT co-culture model and then in mice infected by strains with different immunomodulatory properties. In parallel, SN metabolic profiles were characterized by LC-MS/MS analysis. Then, to identify metabolites responsible of immunomodulations, we correlated both results. The immunomodulatory properties of the identified candidate metabolites were validated via an in vitro T cell polarization assay. Finally, we performed a proof of concept of this immunity modulation induced in vivo by the strains via the administration of metabolites or exometabolomes with immunomodulatory properties opposite to those of the delivered bacteria.
Results :
Interestingly, we have highlighted 3 different immunomodulatory profiles depending on strains: two immunostimulatory clusters (Potentialisation of DC maturation compared to LPS alone for both and one cluster also inducing an increase of co-inhibition markers) and one immunosuppressive cluster (inhibiting DC maturation). Of note, infection of patients by immunosuppressive strains correlates with the decline of respiratory functions. These results were confirmed by LT polarization in vitro and in an infectious murine model showing an induction of a Th17 immune response mediated by the immunostimulatory strains and a Treg response by the immunosuppressive strains. In line with DC phenotypes, untargeted metabolomics analyses of bacterial SN showed 3 distinct metabolic fingerprints, highlighting the importance of Pa strains metabolism in the modulation of immunity. We identified both immunostimulatory and immunosuppressive metabolites that were closely associated with Immunoclusters and validated their immunomodulatory properties. Finally, we were able to show that the Th17 response could be inhibited by the delivery of immunosuppressive metabolites during infection with immunostimulatory strains or restored by the delivery of exometabolome containing immunostimulatory metabolites during infection with immunosuppressive strains.
Conclusion :
This study demonstrate that bacteria are able to modulate host immunity through metabolites secretion upon infection. This highlighted a link between metabolic profiles, immunomodulatory properties of the strains and subsequent clinical outcome of patients. Some of the identified metabolites thus constitute new therapeutic targets for restoring/enhancing host immunity in chronic infectious diseases.
This study provide a full process combining immunoassays and metabolomics for studying host/microbe dialogue and demonstrate its feasibility and relevance.