Insulin-producing b cells in patients with type 1 diabetes (T1D) are destroyed by T lymphocytes. We investigated whether targeting the T-cell receptor (TCR) with a monoclonal antibody (mAb) abrogates T-cell response against residual and newly formed islets in overtly diabetic nonobese diabetic (NOD) mice.NODmice with blood glucose levels of 250 to 350 mg/dL or 350 to 450 mg/dL were considered as new-onset or established overt diabetes, respectively. These diabetic NOD mice were transiently treated with an anti-TCR b chain (TCRb) mAb, H57-597, for 5 days. Two weeks later, some NOD mice with established overt diabetes further received hepatic gene therapy using the isletlineage determining gene Neurogenin3 (Ngn3), in combination with the islet growth factor gene betacellulin (Btc). We found that anti-TCRb mAb (50 mg/d) reversed .80% new-onset diabetes in NOD mice for .14 weeks by reducing the number of effector T cells in the pancreas. However, anti-TCRb mAb therapy alone reversed only ;20% established overt diabetes in these mice. Among those overtly diabetic NOD mice whose diabetes was resistant to anti-TCRb mAb treatment, ;60% no longer had diabeteswhen they also receivedNgn3-Btc hepatic gene transfer 2 weeks after initial anti-TCRb mAb treatment. This combination of Ngn3-Btc gene therapy and anti-TCRb mAb treatment induced the sustained formation of periportal insulin-producing cells in the liver of overtly diabetic mice. Therefore, directly targeting TCRb with a mAb potently reverses new-onset T1D in NOD mice and protects residual and newly formed gene therapy-induced hepatic neo-islets from T-cell-mediated destruction in mice with established overt diabetes.
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