30Autoimmune therapies aim to inhibit autoreactivity while preserving normal immune function. 31 The transcriptional coregulator OCA-B, also known as Bob.1/OBF-1 (gene symbol Pou2af1) is 32 induced in stimulated naïve CD4 + T cells, where it docks with transcription factor Oct1 to 33 regulate genes such as Il2 and Ifng. OCA-B promotes expression of these targets in cases of 34 repeated antigen exposure, a necessary feature of autoimmunity. Polymorphisms in Ocab itself 35 and binding sites for Oct1/OCA-B complexes are associated with multiple forms of 36 autoimmunity including autoimmune (type-1) diabetes. We hypothesized that T cell-specific 37 OCA-B deletion would protect mice from type-1 diabetes, and that pharmacologic OCA-B 38 inhibition would provide similar protection. We developed an Ocab conditional allele and 39 backcrossed it onto a diabetes-prone NOD/ShiLtJ strain background. T cell-specific OCA-B loss 40 protected mice from spontaneous T1D. Protection was associated with reduced pancreatic T cell 41 and macrophage infiltration and reduced proinflammatory cytokine expression. We profiled 42 prediabetic pancreatic lymph nodes and islets by single-cell RNA sequencing and T cell receptor 43 clonotype analysis. Although lymph nodes showed minimal differences, in the islets CD8 + T cell 44 specificities associated with diabetes pathogenesis failed to emerge in OCA-B deficient 45 activated/memory cells. In contrast, CD4 + clones associated with diabetes were present, but only 46 in anergic cells. The protective effect of OCA-B loss was diminished, or even eliminated, using 47 monoclonal models with high affinity to artificial or neoantigens. Rationally-designed 48 membrane-penetrating OCA-B peptide inhibitors normalized glucose levels, and reduced T cell 49 infiltration and proinflammatory cytokine expression in newly-diabetic NOD mice. Together, the 50 results indicate that OCA-B is a potent autoimmune regulator and a promising target for 51 pharmacologic inhibition. 52 54antigens associated with pancreatic beta cells 1, 2 . Pathologically, T1D is characterized by insulitis, beta 55 cell destruction and inability to produce insulin. The main treatment for T1D, life-long insulin therapy, 56 treats symptoms but not cause. The development of new T1D treatments is limited by an incomplete 57 understanding of disease mechanisms 3 . Beta cell regeneration is a promising line of therapy, but still 58 requires methods to specifically block T1D autoimmunity. An ideal method of therapy would be to 59 capture patients early in the disease course and block autoimmunity while keeping normal immune 60 function intact. Such a therapy would spare remaining beta cell function.
61In CD4 + T cells, the transcription factor Oct1 and its cofactor OCA-B regulate a set of ~150 62 target genes, including Il2, Ifng and Csf2 (Gmcsf) 4 . Upon T cell activation, many of these targets are 63 activated by pathways that converge on transcription factors such as NF-AT, AP-1 and NF-kB. Factors 64 like NF-AT can be thought of as the p...
