Tu143 - Enhancing Regulatory T Cell Therapy with Orthogonal IL2-IL2R Systems to Restore Immune Tolerance in Type 1 Diabetes

Huiyun Lyu, Ph.D – University of California, San Francisco; Wendy Rosenthal – University of California, San Francisco; Vinh Nguyen – University of California, San Francisco; Yue Chen – University of California, San Francisco; Kevin Jude, Ph.D – Stanford University; Leon Su, Ph.D – Stanford University; K.Christopher Garcia, Ph.D – Stanford University; Jeffrey Bluestone, Ph.D – University of California, San Francisco & Sonoma Biotherapeutics; Qizhi Tang, Ph.D – University of California, San Francisco

Abstract Text: Regulatory T cell (Treg) therapy aims to restore immune tolerance, but only a small fraction of infused Tregs persist long term. We investigated whether an orthogonal IL2-IL2R system could enhance the persistence and function of Tregs in the NOD mouse model of autoimmune diabetes. A low-affinity orthogonal IL2 ligand, 3A10, induced STAT5 phosphorylation and proliferation selectively in ortho-IL2R+ Tregs at high concentrations in vitro, but failed to aid ortho-IL2R+ islet antigen-specific Tregs in preventing diabetes. While a high-affinity orthogonal IL2 ligand, 1G12, weakly stimulated wt-IL2R at high concentrations. Thus, the selectivity of 1G12 for ortho-IL2R was dose dependent. At low doses, 1G12 prevented diabetes with or without infusion of ortho-IL2R+ islet antigen-specific Tregs. These results show that the use of the ortho-IL2-IL2R system in vivo depended on ortho-IL2's relative intrinsic affinity for wt-IL2R and avidity for ortho-IL2R. To improve the potency and selectivity of the ortho-IL2-IL2R system, we tethered the orthogonal IL2 ligands to the ortho-IL2R via a peptide linker. 3A10 tether selectively promoted greater pSTAT5, CD25 and Bcl2 expression, proliferation, and survival of engineered Tregs in vitro and in vivo when compared to empty vector-expressing Tregs without IL2 and 1G12 tether. However, empty vector-expressing Tregs provided IL2 up-regulated these markers greater than 3A10 tether. Nonetheless, both 3A10 tether and 1G12 tether enabled complete diabetes prevention using as few as 2,000 engineered islet antigen-specific Tregs. Collectively, our study demonstrates that an orthogonal IL2 autocrine system can be an effective cell engineering strategy for augmenting Treg cell therapy for autoimmune diseases.