NOVEL BIOLOGICS PROMOTE STABLE EXPANSION OF REGULATORY CD25HIGH FOXP3+ T LYMPHOCYTES AS A MEANS FOR AN ADOPTIVE CELL-BASED IMMUNOTHERAPY

Abstract

Autoimmune disease arises when a breakdown in immunological self-tolerance causes self-reactive tissue destruction. In Multiple Sclerosis (MS), myelin reactive CD4+ T cells initiate an immune attack on the myelin sheath resulting in a chronic inflammatory demyelinating disease. Like numerous other autoimmune diseases, currently there is no cure. Although the available disease modifying treatments aid in the relief of symptoms, these drugs leave patients vulnerable to opportunistic infections. The development of a targeted therapeutic approach to reestablish self-tolerance is a dire need. CD4+ FOXP3+ regulatory T cells (Tregs) are a subset of T cells that act as immune mediators and play an integral role in controlling autoimmunity. Loss of function or developmental defects in Tregs are associated with systemic, lethal autoimmune disease. Because of the suppressive capabilities, Treg immunotherapies are of interest for clinical translation in treatment of autoimmune diseases and chronic inflammatory diseases. A major hurdle in Treg immunotherapies is the instability of this subset. When propagated in vitro, FOXP3+ Tregs are rapidly overgrown by conventional T cells, lose FOXP3 expression, and/or can revert to an effector T cell phenotype. In this study, we developed novel biologics that were used in vitro and in vivo to stabilize and allow dominant outgrowth of FOXP3+ Tregs. To achieve this, we manipulated the IL-2 environment by which low-zone concentrations of IL-2 favored Treg dominance due to the high constitutive expression of the IL-2 receptor [alpha] chain on Tregs. At low concentrations of our fusion proteins (FPs), a low-zone IL-2 environment was created that allowed for Treg dominance. Through in vitro propagation in the FPs, the Tregs remained stable, continued to express canonical Treg-associated markers, and maintained suppressive activities that inhibited proliferation of responder T cells. The FPs worked synergistically with myelin-specific tolerogenic vaccines in that boosters containing the FPs sustained myelin-specific Tregs over a month-long time course in vivo. These studies provide tools for expanding Tregs in vitro and eliciting Tregs in vivo as a means for a Treg-based immunotherapy for treatment of autoimmune diseases and chronic inflammatory diseases.