Enhanced Immune Response after Subcutaneous Injection of Diphtheria Toxoid-Loaded Bioerodible Microspheres

Abstract

The feasibility of the enhanced immunization with diphtheria toxoid-loaded bioerodible microspheres was examined by investigating the serum antibody levels and lethal test in vivo. PLGA polymer was selected based on the properties such as degradability, tissue compatibility, and ease of particulate preparation. The double emulsion solvent extraction method was employed for the fabrication of microspheres to control the release of diphtheria toxoid. Dichloromethane or ethyl acetate was applied as an organic phase and poly (vinyl alcohol) as a secondary emulsion stabilizer during fabrication procedure. Diphtheria toxoid can be microencapsulated using PLGA copolymer without a loss of its immunogenicity. The results from the in vivo study with bioerodible microsphere indicated that immunogenic response, expressed as ELISA IgG titers, was significantly higher than the conventional antigen for 8 weeks after single injection. Consequently, these microspheres could provide the controlled release of antigens for developing enhanced vaccine formulations as a parenteral carrier system.