Role of TNFR2 expressed by Treg in autoimmune diseases and therapeutic implications – TETRAD

Thanks to the CRE-lox system, we have developed new conditional knockout mouse models to better understand the role of TNF and its effect on Treg and Treg biology in autoimmune diseases. In a multiple sclerosis mouse model, we have shown that TNF stimulates Treg in the central nervous system via its type 2 receptor (TNFR2). Thus, in mice in which the Tregs are deficient for TNFR2 and therefore can no longer respond to TNF, the disease is very severe. In addition, the injection of a nontoxic analogue of TNF has a major therapeutic effect on multiple sclerosis in mice. We also sought to better characterize the molecular mechanisms involved in Treg function during autoimmune diseases. We have identified a major role of NF-kB activation in the function of these cells. Indeed, mice in which the Tregs are deficient for this molecule spontaneously develop an autoimmune syndrome. RNA-Seq data provided a better understanding of the molecular mechanisms involved.

Our work provides insights into how Tregs are able to control autoimmune diseases. Inactivation of Treg stimulation by the TNF / TNFR2 / NFkB pathway leads to an increase in autoimmunity. Indeed, in a mouse model of multiple sclerosis, we observe that the administration of antibodies neutralizing TNF or TNFR2 aggravates the disease. Similarly, mice with conditional knockout of TNFR2 in Treg alone have a more severe disease. We also show that TNF acts directly on Tregs to stimulate them and that this activation is dependent on the activation of NF-kB. Our results show that disease control by Treg stimulation by TNF occurs in the inflamed central nervous system. From a therapeutic point of view, we observe that Treg stimulation by a TNFR2 agonist has a major beneficial effect in this mouse model of multiple sclerosis.

Our work provides insights into the mechanisms involved in the development of autoimmune diseases, including how Tregs are able to control these diseases. In addition, we have demonstrated a new therapeutic molecule, a TNF analogue, which, when administered in mice, has a major beneficial effect in multiple sclerosis by stimulating Treg. We hope to contribute to the development of new treatments for autoimmune diseases in humans.

Scientific publications
• Emilie Ronin et al. The NF-?B RelA transcription factor is critical for regulatory T cell activation and stability. Frontiers in Immunology 2019. fimmu.2019.02487.
• Salomon BL, et al. Tumor Necrosis Factor a and Regulatory T Cells in Oncoimmunology. Front Immunol. 2018. 9:444.
• Baud V and Collares D. Post-Translational modifications of RelB NF-?B subunit and associated functions. Cells. 2016, 5, 22.

Patents
• Prevention or treatment of hematologic malignancy relapse using a TNFR2 antagonist. Inventors: COHEN JL, Salomon BL, Maury S, Leclerc M and Naserian S. EP 16 305 754.0, filed on June 22th, 2016
• Detection of RelB activation as a prognostic marker in B-cell lymphoma, 2019, inventors: Baud V., Nuan-Aliman S.
• Induction of B-cell lymphoma cells death by a combination of antimetabolic drugs, 2019, inventors : Baud V., Thieblemont C., under evaluation.

Autoimmune diseases (AID) are due to a dysfunction of the immune system that attacks a specific organ (organ-specific AID) or multiple tissues (systemic AID). The incidence of these diseases has greatly increased in the last decades. They affect now 5% of the population and cannot be cured, although recent therapeutic progresses have been made. Multiple sclerosis (MS) and type 1 diabetes (T1D) are among the most frequent. The general objective of this project is to improve our understanding of the role of CD4+CD25+Foxp3+ (Tregs) in the pathophysiology of organ-specific AID (MS, T1D) and to propose a new therapeutic approach by targeting these cells.

Tregs play a major role in regulation of AID, notably in the control of T1D and experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. They are strongly activated in the target organs of these diseases allowing to slowdown or limit their progression. The molecular mechanisms of this Treg activation are poorly known. Our recent data suggest a role for TNF. Indeed, this cytokine strongly stimulates the proliferation of Tregs by interacting with its type 2 receptor (TNFR2). In mice that are genetically modified to be deficient in TNFR2 only in Tregs, EAE is exacerbated and Treg expansion is decreased in the inflamed central nervous system. Administration of anti-TNF drugs leads to EAE aggravation. This result is of importance since it reproduces the so far unexplained exacerbation of the disease when anti-TNF drugs have been administrated in MS patients. Moreover, stimulation of Tregs by TNF seems to trigger the non-canonical NF-kB pathway signaling. In this project, we will test the following working hypothesis: During some organ-specific AID, TNF expands Tregs in the target organ by activation of the non-canonical NF-kB signaling pathway, leading to disease control.

Our project is divided in 3 major objectives. The first will be to better understand the role of TNFR2 expressed by Tregs in the control of organ-specific AID by using mice deficient for TNFR2 only in Tregs. We will study the molecular mechanisms responsible for EAE aggravation in these mice and we will assess if TNF controls other AID, such as T1D, by acting on Tregs. The second objective will consist in generating new agonists of human TNFR2, in testing the therapeutic efficacy of an agonist of mouse TNFR2 in EAE and T1D and in studying whether Tregs from MS patients respond normally to TNF. The last objective of the project will be to determine whether the effect of TNF on Tregs is indeed dependent on the activation of the non-canonical NF-kB signaling pathway. We will also study if the Treg expansion in the inflamed CNS during EAE and the putative therapeutic effect of the TNFR2 agonist involve this signaling pathway. This project should improve our basic knowledge of the pathophysiology of AID and may lead to a new therapeutic approach of these diseases.