GAD-alum treatment induces GAD65-specific CD4+CD25highFOXP3+ cells in type 1 diabetic patients

Type 1 diabetes results from autoimmune destruction of insulin producing pancreatic β-cells. We have shown that treatment with alum-formulated glutamic acid decarboxylase 65 (GAD-alum) preserved residual insulin secretion and induced antigen-specific responses in children with recent onset type 1 diabetes. The aim of this study was to further investigate the immunomodulatory effect of GAD-alum, focusing on CD4+CD25high cells and their association to cytokine secretion. Samples obtained 21 and 30 months after the initial injection of GAD-alum or placebo were included in the present study. GAD65-stimulation enhanced the percentage of CD4+CD25highFOXP3+ cells, but reduced the percentage of CD4+CD25+ cells, in samples from the GAD-alum treated group. Further, the GAD65-induced secretion of IL-5, -10, and -13 correlated with the expression of CD4+CD25highFOXP3+ cells, but inversely with CD4+CD25+ cells. These new data suggest that GAD-alum treatment induced GAD65-specific T cells with regulatory features.