OR24-2 Cutting-edge translational strategies in type 1 diabetes

BACKGROUND AND PURPOSE OF THE STUDY: The overall goal of this study is to develop precision-targeted therapies for type 1 diabetes (T1D) by blocking the presentation of pancreatic antigens to T cells using an innovative translational approach. There is currently no curative therapy for T1D and the only available treatment is insulin replacement, which – although being life-saving – remains problematic and can be associated with often fatal high or low glucose levels. We hypothesize that the presentation of pathogenic pancreatic peptides to T cells within the HLA-DQ8 pocket is a key trigger in T1D, and that blocking the peptide binding to this pocket can be harnessed to treat/prevent the autoimmune response targeting beta cells in T1D. We propose to block antigen presentation to treat/prevent autoimmunity in T1D using retro-inverso D-amino acid peptides (RIPs). To test our hypothesis, we used the following tools: recombinant human HLA-DQ8, human B cells homozygous for HLA-DQ8, humanized mice expressing human HLA-DQ8, NOD mice, and peripheral blood mononuclear cells (PBMCs) isolated from new onset HLA-DQ8 T1D patients. All of them represent exquisite translational instruments to evaluate in vitro, ex vivo, and in vivo the functional role of our RIPs in preventing beta cell destruction. SUMMARY OF RESULTS: We have identified a RIP (RI-CT) that inhibits InsB: 9-23 binding to recombinant HLA-DQ8 molecule, as well as its binding to HLA-DQ8 expressed on a human B-cell line. Specifically, RI-CT averted T-cell activation in a mixed lymphocyte reaction containing human DQ8 cells loaded with InsB: 9-23 peptide and murine T-cells expressing a human TCR specific for the InsB: 9-23–DQ8 complex. These results were also confirmed in humanized transgenic B6-DQ8 mice (KO for murine MHC-II) both ex vivo and in vivo, as shown by decreased production of pro-inflammatory cytokines (including IL-2 and IFN-γ) and reduced lymphocyte proliferation. Moreover, RI-CT prevents autoimmune diabetes in NOD mice as demonstrated by a significant decrease in pancreatic immune cell infiltration in treated mice versus controls. Importantly, at 25 weeks of age 70% of RI-CT treated mice were protected from the development of diabetes, while as expected 80% of control NOD mice had developed the disease. Interestingly, RI-CT injection also altered T-cell subpopulations in NOD mice significantly decreasing CD8 expression and significantly increasing Foxp3 levels in treated mice. Of note, RI-CT significantly inhibits InsB: 9-23-mediated lymphocyte activation in peripheral blood mononuclear cells isolated from new onset DQ8-T1D patients. CONCLUSIONS: In summary, we discovered a RIP that blocks InsB: 9-23 binding to HLA-DQ8 and its presentation to T-cells averting beta cells destruction, and that delays T1D in NOD mice. These data set the stage for using our approach of blocking antigen presentation by RIP as a novel therapeutic approach for autoimmune diseases in general. Presentation: Monday, June 13, 2022 11:15 a.m. - 11:30 a.m.