The development and optimization of immune therapies in patients has been hampered by the lack of preclinical models in which their effects on human immune cells can be studied. As a result, observations that have been made in preclinical studies have suggested mechanisms of drug action in murine models that may not be confirmed in clinical studies. We have utilized a humanized mouse reconstituted with human hematopoetic stem cells to circumvent these limitations. We have studied the effects of teplizumab in this model, a Fc receptor non-binding humanized monoclonal anti-CD3 antibody that has been used to treat patients with Type 1 diabetes mellitus. A novel mechanism of action was identified where human gut tropic CCR6+ T cells leave the circulation and secondary lymph organs and migrate to the small intestine. They become producers of IL-10 which can be detected in the peripheral circulation. Blockade of migration of T cells to the small intestine by natalizumab abolishes the treatment effects of teplizumab. Direct translation of these findings was possible in patients with Type 1 diabetes treated with teplizumab since we found there is increased expression of IL-10 by CD4+CD25highCCR6+FoxP3 cells when they emerge into the peripheral circulation. These findings demonstrate that humanized mice may be used to identify novel immunologic mechanisms that occur in patients treated with immune modulators.

The mechanisms whereby immune therapies affect progression of Type 1 diabetes (T1D) are not well understood. Teplizumab, an FcR non-binding anti-CD3 mAb, has shown efficacy in multiple randomized clinical trials. We previously reported an increase in the frequency of circulating CD8+ central memory (CD8CM) T cells in clinical responders, but the generalizability of this finding and the molecular effects of teplizumab on these T cells have not been evaluated. We analyzed data from 2 randomized clinical studies of teplizumab in patients with new and recent onset T1D. At the conclusion of therapy clinical responders showed a significant reduction in circulating CD4+ effector memory (CD4EM) T cells. Afterwards, there was an increase in the frequency and absolute number of CD8CM T cells. In vitro, teplizumab expanded CD8CM T cells by proliferation and conversion of non-CM T cells. Nanostring analysis of gene expression of CD8CM T cells from responders and non-responders vs placebo-treated control subjects identified decreases in expression of genes associated with immune activation and increases in expression of genes associated with T cell differentiation and regulation. We conclude that CD8CM T cells with decreased activation and regulatory gene expression are associated with clinical responses to teplizumab in patients with T1D.

Type 1 diabetes is a common autoimmune disease that affects millions of people worldwide and has an incidence that is increasing at a striking rate, especially in young children. It results from the targeted self-destruction of the insulin-secreting β cells of the pancreas and requires lifelong insulin treatment. The effects of chronic hyperglycemia – the result of insulin deficiency – include secondary endorgan complications. Over the past two decades our increased understanding of the pathogenesis of this disease has led to the development of new immunomodulatory treatments. None have yet received regulatory approval, but this report highlights recent progress in this area.

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SCD measurements are easily determined by US in neonates, with good correlation between weight and MSCD.