A Granzyme B-Cleavable T Cell-Targeted Bispecific Cell Vesicle Connector for Reversing New-Onset Type 1 Diabetes

Type 1 diabetes (T1D) is an autoimmune disorder in which pancreatic β-cells are destroyed by CD8⁺ T cells. Anti-CD3 antibody effectively treats early-stage T1D when β-cell autoantibodies are detected but before symptoms appear. However, it impairs the immune system temporarily, exposing individuals to infection. A therapeutic that can reverse new-onset T1D without harming the immune system remains urgently needed. Herein, we have constructed cellular vesicles presenting granzyme B-responsive fusion proteins (designated aCD8-GrzBcs-IL2) composed of a single-chain variable fragment of anti-CD8 antibodies and a mutein interleukin-2 (IL2). aCD8-GrzBcs-IL2 is designed to simultaneously inhibit CD8⁺ T cells and promote Treg cells, especially when CD8⁺ T cells are attacking β-cells. <i>In vitro</i>, these cellular vesicles can inhibit the cell-killing effect of CD8⁺ T cells and enhance the expansion of Treg cells. Notably, intravenous administration of aCD8-GrzBcs-IL2-expressed cellular vesicles reversed newly onset diabetes in 77.8% of nonobese diabetic (NOD) mice without reducing blood CD3⁺ T cells and CD8⁺ T cells, indicating a favorable safety profile.