Objective
Despite the notion that autoreactive T lymphocytes mediate the destruction of beta cells in pancreatic islets, our knowledge on the development of this population and progression from a benign state to a pathogenic state is still limited. The identification of biomarkers, i.e. molecules that can identify these aggressive T lymphocytes, to follow type 1 diabetes (T1D) progression, is still an unmet need.
In this context, our proposal aims at further characterizing beta-cell-specific autoreactive T lymphocytes not only in the blood, but also in the lymph nodes draining the pancreas of diabetic and non diabetic individuals, the more so since a new subset of T lymphocytes, exhibiting markers and properties of ‘stem’ cells, has been identified in the pancreatic lymph nodes of a mouse model of T1D (NOD). These ‘stem-like’ T lymphocytes are considered as a ‘reservoir’ of mature pathogenic autoreactive T lymphocytes.
Therefore, our objective is to investigate the existence and role of stem-like autoimmune T lymphocytes comparing the blood and pancreatic lymph nodes of T1D patients and non diabetic donors using state-of-the-art technologies. Analysis of beta-cell-specific autoimmune T lymphocytes from cancer patients treated with immune checkpoint inhibitors (ICI), and who have developed fulminant T1D, will provide complementary results. Indeed, ICI neutralize a molecular brake called PD-1 that refrains T lymphocytes from attacking cancer cells, thus promoting anti-tumor responses. Stem-like T lymphocytes are proposed to be the main target of anti-PD-1 ICI. We will gain knowledge on how anti-PD-1 ICI-induced T1D compare with the naturally arising autoimmune disease, and the role played by stem-like T lymphocytes in this acute form of T1D. Lastly, we aim at evaluating the therapeutic potential of targeting autoimmune stem-like T lymphocytes to, contrary to the cancer field, block their maturation into pathogenic T lymphocytes. We will test the safety and efficacy of antibodies that will stimulate the PD-1 brake (already in clinical development in other inflammatory diseases) in vitro and in vivo in a new mouse model of T1D genetically modified to express human PD-1. We will analyze their capacity to inhibit the attack of T lymphocytes against beta cells and to protect from T1D development.
This work will provide a better understanding of the mechanisms sustaining benign versus pathological islet autoimmunity, and novel T-cell biomarkers and therapeutic targets for T1D.
Background Rationale
Type 1 diabetes (T1D) is an autoimmune disease resulting from the destruction of pancreatic beta cells by the immune system, in particular by autoreactive T lymphocytes, leading to dysregulated glucose homeostasis. We and other groups documented that these autoreactive T lymphocytes are detected at similar frequencies in the blood of all individuals, irrespective of their T1D or healthy status. In contrast, a significant fraction of autoreactive T lymphocytes is detected only in the pancreas of T1D patients where they kill beta cells. This data suggests that a state of “benign” islet autoimmunity exists in all individuals and becomes pathogenic in diseased patients by acquiring new features, notably the capacity to home to the pancreas target organ and acquire pathogenic functions.
Recently, a new subset of autoimmune T lymphocytes has been identified in the pancreatic lymph nodes of a mouse model of T1D (the NOD mouse), exhibiting markers and properties of ‘stem’ cells. These ‘stem-like’ T lymphocytes have a high capacity to self-renew and they are proposed to be a ‘reservoir’ that can continuously replenish the pool of mature pathogenic T lymphocytes migrating in the pancreas and destroying β cells.
If data on T lymphocytes exhibiting a stem-like profile and function in autoimmunity in general, and more specifically in T1D, are very limited, they have more extensively been described in cancer and chronic infections. In cancer, they present a unique profile and are mostly located in the lymph nodes draining the tumor and the tumor itself. Of interest, data showed that they are the main targets of cancer immunotherapy using immune checkpoint inhibitors (ICI). These ICI are antibodies that neutralize a molecular brake called PD-1 that refrains T lymphocytes from attacking cancer cells, thus promoting anti-tumor responses. Anti-PD-1 ICI therapy has been shown to act on anti-tumor stem-like T lymphocytes and promote their switch into pathogenic T lymphocytes, killing cancer cells. If ICI therapy is very efficacious for the treatment of some cancers, it can also induce adverse events such as autoimmune diseases, including T1D. In most cases, T1D onset is fulminant, from 1 week to a couple of months post ICI administration, with patients presenting with severe hyperglycemia. Similarly to anti-tumor T lymphocytes, this fulminant T1D may result from the targeting of stem-like autoimmune T lymphocytes by anti-PD-1 ICI.
Based on all these human and mouse data, our hypotheses are 1) that the stem-like subset of autoimmune T lymphocytes may underlie the progression of benign islet autoimmunity toward T1D; 2) that this progression is favored by anti-PD-1 ICI therapy; and 3) that such progression may instead be blunted by novel therapies that will stimulate this PD-1 brake, thus inhibiting the attack of T lymphocytes against beta cells and protecting from T1D development. In line with this last point, several antibodies stimulating PD-1 are currently tested in clinical trials for several inflammatory diseases.
Description of Project
Type 1 diabetes (T1D) is an autoimmune disease resulting from the destruction of pancreatic beta cells by the immune system, in particular by autoreactive T lymphocytes. Data from our laboratory and others indicate that a universal state of ‘benign’ islet autoimmunity may exist in healthy individuals. In this benign state, autoreactive T lymphocytes circulate in the blood but do not drive beta-cell destruction. Currently, it is unknown why some individuals maintain benign islet autoimmunity, while others develop T1D. Understanding the biological pathways responsible for a switch between benign and pathological islet autoimmunity has the potential to unravel biomarkers of early disease initiation and therapeutic targets to prevent or delay T1D.
Recently, in the NOD mouse model of T1D, a new subset of autoimmune T lymphocytes has been identified in pancreatic lymph nodes (PLNs). They exhibit some “stem” properties, namely a high capacity to self-renew and continuously give rise to mature T lymphocytes, which are the ultimate killers of beta cells. These ‘stem-like’ T lymphocytes have also been described in cancer and chronic infections. Of interest, they are the main targets of cancer immunotherapy using immune checkpoint inhibitors (ICI). These ICI neutralize a molecular brake called PD-1 that refrains T lymphocytes from attacking cancer cells, thus promoting anti-tumor responses. This caught our attention as a fulminant form of T1D is a well-known adverse event of ICI in some cancer patients.
Our hypotheses are that: 1) stem-like autoimmune T lymphocytes may underlie the progression of benign islet autoimmunity toward T1D; 2) this progression is favored by ICI therapy that neutralizes the PD-1 molecular brake on autoimmune T lymphocytes; and 3) that such progression may instead be blunted by novel therapies that stimulate this PD-1 brake, thus inhibiting the attack of T lymphocytes against beta cells and protecting from T1D development.
We will address each of these three hypotheses using a) blood and pancreatic lymph nodes from T1D patients, non diabetic control donors, and from cancer patients having developed T1D after ICI therapy, and b) human in vitro functional assays and in vivo mouse models of T1D to investigate the existence, role and possible targeting of stem-like autoimmune T lymphocytes. This work will provide a better understanding of the mechanisms driving benign autoimmunity toward T1D, and will provide novel T-cell biomarkers and therapeutic targets for T1D.
Anticipated Outcome
First, by analyzing blood and pancreatic lymph nodes of type 1 diabetic (T1D) and non diabetic donors, we expect to provide a deeper characterization of beta-cell-specific autoreactive T lymphocytes, and in particular define the existence of a stem-like subset, which may feed the pool of pathogenic T lymphocytes and sustain islet autoimmunity. We will verify whether these stem-like T lymphocytes are mostly/exclusively present in the pancreatic lymph nodes or also detectable in blood, and whether they segregate differently in T1D and healthy donors.
Second, we expect that results gathered from cancer patients developing or not fulminant T1D after treatment with immune checkpoint inhibitors neutralizing PD-1 (anti-PD-1 ICI) will complement these analyses by investigating modifications in beta-cell-specific T lymphocytes induced in this ‘acute’ condition. We also anticipate to provide a better understanding of how anti-PD-1 ICI-induced T1D compare with the naturally arising autoimmune disease, which may guide the treatment and monitoring of this adverse event.
Third, using a humanized mouse model of T1D that we are generating, we expect to demonstrate the therapeutic effects of antibodies that stimulate the PD-1 brake on pathogenic autoreactive T cells and to unravel their mode of action. We believe these effects will translate into prevention or delay diabetes onset.
Relevance to T1D
Type 1 diabetes (T1D) is increasing at a rate of ~4%/year in most industrialized countries, and affects 1.2 million persons under 20 years worldwide in 2021, with 150,000 new cases each year (International Diabetes Federation, 10th report 2021).
The current management of T1D is focused on the metabolic consequences of the disease, without impacting disease mechanisms. A more rational approach should target the underlying autoimmune disease, before β-cell destruction and clinical disease. To this end, we need to understand how the autoimmune process develops and progresses toward T1D, and how to halt this progression.
Our proposal addresses this unmet need by further exploring the pool of autoreactive T lymphocytes and in particular the recently described stem-like subset which may constitute a ‘reservoir’ giving rise to mature pathogenic T lymphocytes migrating in the pancreas and destroying beta cells. Our investigations, not only the blood but also the lymph nodes draining the pancreas of T1D and non diabetic donors will provide novel insights into the mechanism sustaining the development of aggressive autoimmune T lymphocytes and identify biomarkers that may distinguish the pathogenic beta-cell-specific T lymphocytes of T1D patients from their ‘benign’ counterpart in all individuals, and may help to follow T1D progression.
Analysis of beta-cell-specific autoimmune T lymphocytes from cancer patients treated with immune checkpoint inhibitors (ICI) immunotherapy neutralizing the molecular brake PD-1, and who have developed fulminant T1D, will provide complementary results as anti-PD-1 ICI target stem-like T lymphocytes. Our findings will also provide a better understanding of how ICI-induced T1D compare with the naturally arising autoimmune disease, which may guide the treatment and monitoring of this adverse event. This is critical due to the impressive clinical results obtained with ICI, which led to FDA approval for more than 25 types of tumors.
Lastly, the relevance of this proposal to T1D patients is to propose a new therapeutic strategy to treat prediabetic stage 1/2 patients using novel agents that will stimulate the PD-1 molecule, thereby blocking the development of pathogenic autoimmune T lymphocytes and protecting from T1D development. Of importance, several of these new therapeutics are currently in clinical development in other inflammatory diseases, supporting the feasibility of this approach for T1D prevention.