Our goal is to enhance the efficacy of DNA vaccines using new bio-organic compounds to mediate delivery. Live vaccines have always been more effective than DNA vaccines in clinical trials, but recent technology allowing DNA delivery to specific cells provides new possibilities for DNA vaccines. Here we propose to test DNA vaccines for targeted delivery to dendritic cells (DC) using novel glyco-polyamines as the delivery vehicle. DC are the primary antigen-presenting cells and they express abundant cell surface carbohydrate receptors, such as mannose receptor and DC-SIGN. The cyclodextrin-based glyco-polyamines used in our studies consist of two functional domains: the multiple amino groups that bind and form complexes with DNA, and the sugar ligands that bind cell surface lectins and target the DNA complexes to DC. Enhancing the uptake of DNA by DC will enhance the immunogenicity of DNA vaccines. Cell culture studies have already demonstrated that mannosylated polyamines significantly enhance the uptake of plasmid DNA into DC. Here we propose to test the efficacy of targeted delivery in vivo. We hypothesize that DNA vaccines targeted to the cell surface carbohydrate receptors of dendritic cells will elicit enhanced cell-mediated responses. To test this hypothesis, we will initially employ the LCMV-infected murine model system that is known to elicit strong cell-mediated immune responses. We will have two specific aims.
In aim 1, we will synthesize novel glycosylated cyclodextrin-based polyamines (CDPA) and test the uptake and expression of reporter genes in dendritic cell culture. Mannose and oligomannose ligands will be introduced into CDPA for targeting to mannose receptors and DC-SlGN on dendritic cells, respectively.
In aim 2, we will test the magnitude of cell mediated immunity after oral inoculation with DNA vaccines in various formulations. Plasmid DNA encoding the LCMV GP gene will be orally delivered to mice as naked DNA or as DNA complexed with CDPA or glycosylated CDPA. Once we find a formulation that is optimum for eliciting cell-mediated immunity, we will replace the LCMV-GP gene with DNA encoding antigens associated with protective immunity in Lassa fever (Lassa NP and GP genes). We will determine, in the murine system, whether DNA complexed with our compound can still elicit strong cell-mediated immune responses. Once we have optimized the vaccine formulation in the murine model system, we will apply the targeted delivery system to monkey models and human clinic trials. These studies will lead to improved vaccines against Lassa fever and new compounds that will be useful for cell-specific delivery.
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