623. Polymer Microparticles Delivering a Idiotype/Chemokine Fusion DNA Vaccine Generate Protective Immunity in a Mice Model of B Cell Lymphoma

Abstract

Top of pageAbstract Introduction: We earlier demonstrated that branched Polyethyleneimine (PEI) conjugated poly(lactide-co-glycolide)PLGA microparticles enhanced transfection in phagocytic RAW cells in vitro.1 We present herecomparison of the effects of linear and branched PEI conjugated PLGA microparticles in enhancing the potential of a model idiotype/chemokine fusion encoding genetic vaccine for B cell lymphoma in mice models. Branched PEI70kDa polymer conjugated PLGA microparticles in comparison with linear PEI conjugated microparticles; a) better adsorbed plasmid DNA b) showed significant adjuvant effects by upregulating MHC class II and CD80 molecules in macrophage cells and finally c) demonstrated enhanced anti tumor effects upon challenge with an A20 B cell lymphoma tumor in Balb/C mice in vivo. Branched PEI70kDa conjugated PLGA microparticles imparted anti tumor effects which were comparable or slightly better than gene gun mediated immunization, especially when administered intramuscularly. Materials and Methods: Synthesis of cationic microparticles and characterization was performed as described earlier1. FACS studies were conducted using fluorescent antibodies such as MHC class II, CD80, F4/80 (Ebiosciences, CA) were used to stain RAW264.7 murine macrophage cells (ATCC, VA) post formulation stimulation. Balb/c mice 8-10 weeks old were injected 3 times with cationic microparticles and with gene gun based approaches. A20 tumors were injected at 2.5 times the minimal lethal dose. Survival rates of mice (anti tumor effects) were followed and plotted to confirm statistical significance. Results and Discussion: Plasmid DNA adsorbed on 70kDa branched PEI modified PLGA microparticles demonstrated significant upregulation of MHC class II and CD80 molecules in RAW macrophage cell lines in vitro. These results were also consistent with potent anti tumor effects in vivo. Intramuscular injections of cationic microparticles with adsorbed vaccine encoding plasmid DNA demonstrated anti tumor effects which were comparable with long established gene gun based approaches. Intramuscular injections of cationic particle based formulation proved to be superior to intradermal injections. Conclusions: Cationic PEI conjugated PLGA microparticles could offer an attractive strategy to enhance the immunogenecity of weak self antigens encoded by cancer DNA vaccines. We hypothesize that these alternative approaches with injectable formulations offer more flexibility in terms of introducing additional adjuvants such as synthetic MPL-A and CpG optimized oligos which could significantly further enhance the potential of these cancer genetic vaccines. Current studies are underway to test these enhanced anti tumor effects by co-administration of soluble adjuvants.