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) 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). Three types were synthesized, low valency SAgA (2 insulins per HA), medium valency SAgA (4 insulins per HA), and, high valency SAgA (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 molecules were successfully used to affect the biologic activity of IBCs by inducing desensitization of the B cell antigen receptors (BCR). SAgA 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, but not HA alone, rendered the IBCs refractory to restimulation. SAgA induced a decrease in BCR expression and IP3R-mediated intracellular calcium release. Surprisingly, SAgA binding to BCR on the surface of IBCs induced the observed effects at both high and low SAgA valency. Future studies aim to test the effects of SAgA on disease progression in the VH125.NOD mouse model of T1D.