Antigen-Specific Chimeric Antigen Receptor-T Regulatory Cells Home to Human Islets, Suppress Cytotoxic T Lymphocytes and Reverse Type 1 Diabetes

<b><i>Background:</i></b> We have developed pancreatic beta-cell, antigen-specific, chimeric antigen receptor (CAR) T regulatory cells (Tregs) and explored their therapeutic potential for type 1 diabetes (T1D)/latent autoimmune diabetes of adults (LADA) in human pancreatic tissues ex vivo, and in a spontaneous humanized mouse model (T1D mice) in vivo. <b><i>Results:</i></b> Using live-cell imaging, we observed these glutamic acid decarboxylase, 65 kD isoform (GAD65)-CAR-Tregs home to human pancreatic islets exvivo and proliferate upon encountering the cognate GAD65 antigen in the islets. Furthermore, human pancreatic-islet activated GAD65-CAR-Tregs also suppressed human T1D cytotoxic T lymphocytes in co-cultures. We confirmed these findings in vivo, in a spontaneous humanized T1D mouse model (T1D mice) by showing that mouse GAD65-CAR-Tregs also suppressed diabetogenic T responsive (Tresp) cells and were superior to normal Tregs. We also show that mouse GAD65-CAR-Tregs homed to mouse pancreatic islets in vivo. Moreover, we conducted a 30-day preclinical trial in T1D mice, and observed normalization of fasting blood glucose, fasting insulin, and glucose tolerance tests in GAD65-CAR-Treg-treated T1D mice. We confirmed by histology, the advancement of Tregs, retreat of T effector cells in GAD65-CAR-Treg-treated mice, that led to the recovery/reconstitution of pancreatic islets. <b><i>Discussion:</i></b> Taken together, human GAD65-CAR-Tregs homed to human islets, suppressed diabetogenic T cells, and when used to treat T1D mice that mimic the human pathophysiology of T1D, GAD65-CAR-Tregs reversed T1D. Conceivably, the treatment of T1D with GAD65-CAR-Tregs will allow for recovery/reconstitution of beta cells in human patients as well.