Combinatorial delivery of immunosuppressive factors to dendritic cells using dual-sized microspheres

Microparticulate systems are beginning to show promise for delivery of modulatory agents for immunotherapeutic applications which modulate dendritic cell (DC) functions. Co-administration of multiple factors is an emerging theme in immune modulation which may prove beneficial in this setting. Herein, we demonstrate that localized, controlled delivery of multiple factors can be accomplished through poly (lactic-co-glycolic acid) (PLGA) microparticle systems fabricated in two size classes of phagocytosable and unphagocytosable microparticles (MPs). The immunosuppressive ability of combinatorial multi-factor dual MP systems was evaluated by investigating effects on DC maturation, DC resistance to LPS-mediated maturation and proliferation of allogeneic T cells in a mixed lymphocyte reaction. Phagocytosable MPs (~2 μm) were fabricated encapsulating either rapamycin (RAPA) or all-trans retinoic acid (RA), and unphagocytosable MPs (~30 μm) were fabricated encapsulating either transforming growth factor beta-1 (TGF-β1) or interleukin-10 (IL-10). Combinations of these MP classes reduced expression of stimulatory/costimulatory molecules (MHC-II, CD80 and CD86) in comparison to iDC and soluble controls, but not necessarily to single factor MPs. Dual MP-treated DCs resisted LPS-mediated activation, in a manner driven by the single factor phagocytosable MPs used. Dendritic cells treated with dual MP systems suppressed allogeneic T cell proliferation, generally demonstrating greater suppression by combination MPs than single factor formulations, particularly for the RA/IL-10 MPs. This work demonstrates feasibility of simultaneous targeted delivery of immunomodulatory factors to cell surface receptors and intracellular locations, and indicates that a combinatorial approach can boost immunoregulatory responses for therapeutic application in autoimmunity and transplantation.