(61c) Inhibition of Glycolysis in the Presence of Antigen Generates Antigen Specific Treg Responses in Rheumatoid Arthritis

Introduction: T cells regulate immune homeostasis by generating specific inflammatory or anti-inflammatory immune responses. However, immune dysregulation and over activation of inflammatory T cells can induce autoimmune diseases such as Rheumatoid Arthritis (RA). Antigen-specific enrichment of immunosuppressive regulatory T-cells (Tregs) and reduction of antigen-specific T-effector cells (Teff) can prevent the progression of RA. Notably, dendritic cells (DCs) are effective modulators of antigen-specific T-cell responses. Interestingly, activated DCs and T-effector cells, such as T-helper 1 (Th1) and T-helper 17 (Th17), utilize glycolysis for their energy needs while Tregs rely on fatty acid oxidation for their energy needs. Current RA therapies do not target the root cause of RA or address the antigen specific immune responses against synovial tissue. We hypothesize that blocking DC glycolysis and simultaneous antigen expression may lead to the generation of tolerogenic DCs (tDCs) and subsequent antigen specific Treg induction. Here we show a method where local delivery of an antigen specific therapy can generate antigen-specific Tregs and reduce antigen-specific Th17, Th1 and autoantibodies in a collagen-induced arthritis (CIA) mouse model of RA.

Materials and Methods: Metabolite-based polymeric particles were generated by oil in water emulsions. Scanning Electron Microscopy and Dynamic Light Scatter determined the size of microparticles (MPs). Nuclear Magnetic Resonance and release kinetics assessed the rate of polymer degradation. In vitro studies of immunofluorescence, enzyme-linked immunosorbent assay and flow cytometry determined MP modulation of adaptive immune responses. A DBA/1j CIA mouse model was injected with 1mg of MPs for prevention and treatment studies. These mice were then sacrificed on day 30, and the blood, spleen and lymph nodes (LNs) were harvested to analyze the presence of antigen specific autoantibodies, T cells, and antigen specific T cells.

Results and Discussion: The MPs were determined to be about 1μm and were shown to degrade in a sustained manner. Flow cytometry confirmed that the intracellular delivery of PFK15 and bc2 via paKG particles induced tDCs. In vivo studies demonstrated that the PFK15+bc2 treatment group had lower thickening of the ankle, less antigen specific autoantibodies and an increased population of proliferating Tregs. Additionally, the PFK15+bc2 prevention group had an increased population of antigen specific Tregs and number of proliferating Tregs in the popliteal LNs. Notably, the no treatment group and PFK15+bc2 treatment groups had elevated levels of antigen specific Th1 and Th17 pro-inflammatory cells compared to the prevention group, which had undetectable levels.

Conclusions: The immune non-activating metabolite-based MPs modulate DC function and subsequently alter antigen specific T cell immune responses in mice. This data suggests that the local delivery of PFK15+bc2 via paKG MPs is a viable strategy to prevent RA progression and development.