(251b) Optimizing Combinations of Immune Inhibitors and Agonists to Generate Tolerogenic Antigen Presenting Cells

Natural immune tolerance to self-antigens is maintained via T regulatory cells (Tregs), which actively surveil peripheral tissues or instruct naïve T cells in the thymus to remove or promote anergy of antigen specific T and B cells. This makes Tregs attractive targets for autoimmune therapies, but endogenous differentiation of de novo Tregs or ex vivo differentiation and reintroduction of Tregs has not been successful to date. A new strategy involves generating tolerogenic antigen presenting cells (APCs), which can instruct naïve T cells to differentiate into Tregs; however the types of immunosuppressant drugs used to generate tolerogenic APCs often triggers cell death or has off target effects on unrelated immune interactions. We have recently shown that combinations of both immunosuppressing and immune activating signals can induce longer lived tolerogenic APC populations that can effectively induce Tregs. This presentation will describe the efforts to optimize this combination through mining the data of a large screening library. RAW cells (a mouse macrophage cell line) were screened against a library of over 40,000 combinations of immunomodulators and immune agonists and their NF-kB and IRF3 activity measured. A smaller 10,000 combination library was also screened against THP-1 cells (a human monocyte cell line) for cytokine release. A subset of these combinations with low NF-kB and IRF3 activity as well as low inflammatory cytokine secretion, indicating more tolerogenic phenotypes, were further tested for tolerogenic cytokine release profiles and tolerance markers, such as high IL-10 and PD-L1. Finally, these combinations were tested on primary DCs isolated from mice to determine optimal tolerogenic APC generating formulations. These optimized drug combinations have translational potential for autoimmune diseases.