Modifying immune responses via targeted delivery to dendritic cells
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Dendritic cells (DCs) are critical for initiating innate immune responses resulting in subsequent activation of adaptive immunity. DCs can activate naive T cells to become effector T cells and are crucial in mediating immune responses to pathogens. DCs are also involved in the maintenance of peripheral tolerance, eliminating self-reactive T cells from the periphery thereby preventing autoimmunity. Since DCs play such a pivotal role in regulating immune responses they are attractive cellular targets for immune-modifying reagents.;We have selected an RNA-aptamer specific for the DEC205 receptor, which is highly expressed on a subset of DCs. We have characterized this DEC205-aptamer (min.2) and demonstrated its specificity for DEC205+ DCs in vitro and in vivo. Injection of min.2 conjugated to a model antigen (min.2-OVA) in combination with the TLR3 agonist polyinosinic:polycytidylic acid (pIC) resulted in specific uptake by DCs and activation of OVA-specific T cells. Injection of min.2-OVA admixed with pIC caused regression of established OVA-expressing B16 flank tumors. We are developing this aptamer as a potential vaccine.;We are also developing lipid nanoparticles (LNPs) coated with a single-chain antibody (scFv) specific for DEC205 to target LNP-encapsulated cargoes to DCs. We have shown functional delivery of siRNAs targeting CD40, CD80, and CD86 to DCs resulting in inhibition of activation of DEC205+ DCs and downstream T cell stimulation. Specifically, we demonstrated delivery of the siRNA cargo to DEC205+ DCs in situ. We showed that uptake of siRNAs resulted in gene-specific knockdown via the RNA interference pathway and reduced mixed lymphocyte reaction (MLR) responses when targeted DCs were used as stimulators. We are exploring the potential use of this LNP platform as a therapeutic agent for treating or inhibiting autoimmune diseases.