Soluble Antigen Arrays for Selective Desensitization of Insulin-Reactive B Cells

Autoimmune diseases are believed to be highly dependent on loss of immune tolerance to self-antigens. Currently, no treatments have been successful clinically in inducing autoantigen-specific tolerance, including efforts to utilize antigen-specific immunotherapy (ASIT) to selectively correct the aberrant autoimmunity. Soluble antigen arrays (SAgAs) represent a novel autoantigen delivery system composed of a linear polymer, hyaluronic acid (HA), displaying multiple copies of conjugated autoantigen. We have previously reported that soluble antigen arrays displaying proteolipid peptide (SAgA PLP ) induced tolerance to this specific multiple sclerosis (MS) autoantigen. Utilizing SAgA technology, we have developed a new ASIT as a possible type 1 diabetes (T1D) therapeutic by conjugating human insulin to HA, known as soluble antigen array insulin (SAgA Ins ). Three types were synthesized, low valency lv SAgA Ins (2 insulins per HA), medium valency mv SAgA Ins (4 insulins per HA), and, high valency hv SAgA Ins (9 insulins per HA), to determine if valency differentially modulates the ex vivo activity of insulin-binding B cells (IBCs). Extensive biophysical characterization was performed for the SAgA molecules. SAgA Ins molecules were successfully used to affect the biologic activity of IBCs by inducing desensitization of the B cell antigen receptors (BCR). SAgA Ins bound specifically to insulin-reactive B cells without blocking epitopes recognized by antibodies against the Fc regions of membrane immunoglobulin or CD79 transducer components of the BCR. Preincubation of IBCs (125Tg) with SAgA Ins , but not HA alone, rendered the IBCs refractory to restimulation. SAgA Ins induced a decrease in BCR expression and IP3R-mediated intracellular calcium release. Surprisingly, SAgA Ins binding to BCR on the surface of IBCs induced the observed effects at both high and low SAgA Ins valency. Future studies aim to test the effects of SAgA Ins on disease progression in the VH125.NOD mouse model of T1D.