Objective
The research plan is based on our preliminary data, which used a comprehensive and unbiased approach, to characterize the full antigenic landscape of the proteins targeted in inflamed human pancreatic islets. In addition to the published literature, which only captured less than a hundred peptides we were able to characterize thousands of peptides presented by the inflamed islets. Among the identified antigens some were previously well-characterized T1D-associated autoimmune epitopes, however, the large majority were novel candidate autoantigens to be further characterized. In this application we propose to analyze how these novel self-antigens are generated and how they can activate the immune system and direct a destructive response towards the islet cells in the pancreas. Additionally, a full characterization of the immune cells specific for these peptides will also be performed. The data generated from this application will help designing therapeutical interventions aimed at reducing the generation of islet autoantigens targeted by the activated immune cells.
Background Rationale
Type-1 diabetes (T1D) results from immune-mediated destruction of islet beta cells within the pancreas, which leads to the inability of the body to produce insulin, dysregulation of glucose metabolism, and disabling and potentially life-threatening damage to organs throughout the body. Development of new methods for early T1D diagnosis and new clinical approaches to arrest the autoimmune response are limited by a lack of information on T1D-associated epitopes targeted by islet-infiltrating T cells. We propose to identify tissue- and disease- specific processes that lead to the generation of self-epitopes targeted by regulatory and pathogenic T cell responses.
Description of Project
Type 1 diabetes is an autoimmune disease caused in part by destruction of insulin- producing beta cells in the pancreas by white blood cells called T lymphocytes, which recognize the beta cells as foreign and attack them as if they were viruses or bacteria infecting the body. There is an alarming trend that the number of people with type 1 diabetes is rising. In the U.S. alone, type 1 diabetes may affect as many as 3 million people with a 3-5% annual increase in newly diagnosed cases. Research proposed in this project will identify the antigenic peptide spectrum presented by MHC molecules in inflamed pancreatic islets targeted by autoimmune T cells in type 1 diabetes and determine what these T lymphocytes recognize in the pancreas, and what causes them to initiate autoimmune responses. This research will lead to a better understanding of the autoimmune response in type 1 diabetes and could be harnessed to improve its diagnosis. Additionally, based on the generated data, in the future, we will design therapies aimed at targeting the type 1 diabetes antigenic landscape to decrease the islet targeting by autoreactive T cells.
Anticipated Outcome
Our research aims to fill a critical gap in our understanding of the etiology of type 1 diabetes, specifically, whether islet-infiltrating autoreactive T cells primarily target unmodified or modified self-peptides. The modified peptides derive from the ongoing metabolic and oxidative stress within the islet cells, as such they may generate modified proteins, not present in healthy cells. Identifying these proteins and understanding their role in promoting autoimmunity is pivotal not only to a better understanding of the disease pathogenesis but also towards developing novel therapies. Indeed. many of these oxidative modifications can be reduced by decreasing the ongoing cellular oxidative stress. Altogether, the study will aid in further deciphering the immune responses to human pancreatic beta cells and laid the background work to target these responses to decrease autoimmunity.
Relevance to T1D
Few previous studies have characterized naturally processed peptides, presented by islet cells in the pancreas in the context of T1D to help identify autoimmune epitopes and gain insight into T1D pathogenesis. In addition to these studies, we analyzed primary human pancreatic islet preparations and characterized thousands of naturally processed peptides bound by human MHC-I and MHC-II molecules. Altogether we identified a set of >900 new potential autoimmune epitopes from >400 source proteins not previously shown to be targeted by autoimmune T cells in T1D. Additionally, we also identified several oxidative modifications and advanced glycation end-products, which indicate how islet cells undergo metabolic and oxidative stress which can generate modified proteins. Modified processed proteins can be recognized by autoreactive T cells and facilitate autoimmunity. Overall, our plan is to identify and characterize T1D-associated pathogenic T cells activated by these novels, never reported autoantigens. This will greatly expand the immunological landscape of actionable target for T1D immunotherapy. Indeed, differently from endogenous “naked” diabetogenic self-peptides, peptides with oxidative modifications can be targeted by reducing the number of specific moieties derived from metabolic and oxidative stress. Enzymes, removing specific modifications are already employed in the treatment of autoimmune diseases, such as Rheumatoid Arthritis. Our future plan is to harness the acquired knowledge on the antigenic landscape of peptides presented by inflamed islet towards novel therapies that target immune autoreactivity.