Vaxfectin enhances the humoral immune response to plasmid DNA-encoded antigens

This report characterizes Vaxfectin, a novel cationic and neutral lipid formulation which enhances antibody responses when complexed with an antigen-encoding plasmid DNA (pDNA). In mice, intramuscular injection of Vaxfectin formulated with pDNA encoding influenza nucleoprotein (NP) increased antibody titers up to 20-fold. to levels that could not be reached with pDNA alone. As little as 1 mug of pDNA formulated with Vaxfectin per muscle resulted in higher anti-NP titers than that obtained with 25 mug naked pDNA. The antibody titers in animals injected with Vaxfectin-pDNA remained higher than in the naked pDNA controls for at least 9 months. The enhancement in antibody titers was dependent on the Vaxfectin dose and was accomplished without diminishing the strong anti-NP cytolytic T cell response typical of pDNA-based vaccines. In rabbits, complexing pDNA with Vaxfectin enhanced antibody titers up to 50 fold with needle and syringe injections and also augmented humoral responses when combined with a needle-free injection device. Vaxfectin did not facilitate transfection and/or increase synthesis of beta -galactosidase reporter protein in muscle tissue. ELISPOT assays performed on bone marrow cells from vaccinated mice showed that Vaxfectin produced a three- to five-fold increase in the number of NP-specific plasma cells. Thus. Vaxfectin should be a useful adjuvant for enhancing pDNA-based vaccinations. (C) 7001 Elsevier Science Ltd. All rights reserved.