Role of TNFR2 and 4-1BB expressing Treg in inflammatory diseases – TRINDI

The aim of our project is to better understand the mechanisms of suppression of Foxp3 regulatory T cells (Tregs) in certain inflammatory diseases such as multiple sclerosis, colitis or cancers. For this, we will use genetically modified mice in which the expression of the TNFR2 and 4-1BB co-stimulatory molecules, as well as the transcription factor Eomes, will be specifically deleted in the Tregs following the administration of a pro-drug. Our results show that the ablation of TNFR2 in Tregs (TNFR2?Treg mice) has no effect at steady state but leads to a strong increase in inflammation in models of multiple sclerosis, colitis or cancer, with worsening of symptoms for the first two diseases and tumor rejection for the third, which indicates an alteration in the Treg function in inflammatory conditions. In a 1st part of the project, we will characterize the Tregs of inflamed tissues in these three pathologies in TNFR2?Treg and control mice by an approach of RNA sequencing on single cells (scRNA-Seq) and flow cytometry. This work should make it possible to characterize new subpopulations of Tregs playing a preponderant and specific role in the control of these diseases. We will also study the specific role of 4-1BB expressed by Tregs in these diseases. Based on preliminary data suggesting a specific role of Eomes in Tregs, part 2 of the project will be devoted to the study of this molecule in the ability of Tregs to control the same inflammatory diseases. For this, we will use mice in which Tregs will be deficient for Eomes and / or TNFR2. Part 3 will be devoted to the study the effects of Tregs on target immune cells in inflamed tissues in the three pathological models induced in TNFR2?Treg mice. Again, we will use scRNA-Seq and flow cytometry approaches. We will pay particular attention to Eomes, this time for its role in conventional T cells, through genetic ablation and overexpression approaches. In the last part of the project, we will study the modes of action of agonists and antagonists of TNFR2 and 4-1BB which have a therapeutic effect in autoimmune diseases and cancers (already tested in clinical trials of immunotherapies) and whose mode of action is still poorly understood. Thanks to our conditional ablation models of TNFR2 or 4-1BB in Tregs, we will be able to determine whether these molecules act by direct effect on Tregs.
Our project will thus has an impact on several aspects of the biology of Tregs in inflammatory diseases. Through single-cell analyzes, we believe we can identify the subpopulations of Tregs in inflamed tissues that play a major role in the control of these diseases. We could find out if the same subpopulations control different inflammatory diseases and cancers. We will also be able to improve our understanding of the role played by TNFR2 and 4-1BB in the biology of Tregs and better understand the role played by Eomes expressed by Tregs and conventional T cells in these diseases. We should also improve our knowledge of the suppressive effect of Tregs on other immune cells in inflamed tissue. Finally, we will determine whether the therapeutic action of TNFR2 and 4-1BB agonists has a direct effect on Tregs. Overall, this project should provide a better understanding of how Tregs regulate these inflammatory diseases, which could pave the way for new therapeutic strategies for these pathologies.