(680f) Encapsulation of Model Antigens Into Microparticles Results in Dosage Sparing Capabilities

Biodegradable polymer particles have been studied as carriers for drugs, proteins, and antigens. Using surface-erodible polyanhydride microparticles as adjuvants, the goal of this work was to define the immune response resulting from immunizing mice with a weakly immunogenic model antigen encapsulated into polyanhydride microparticles twelve weeks post immunization in comparison with an equivalent soluble antigen dose. Microparticles of varying ratios of 1,6-bis(p-carboxyphenoxy)hexane (CPH) and sebacic acid (SA) encapsulating the model antigen ovalbumin (OVA) were fabricated using either a modified solid/oil/oil double emulsion method or cryogenic atomization. C3H mice received immunizations of 0.5 micrograms of microparticles and immunological serum antibody responses were monitored biweekly for twelve weeks post injection. Encapsulated microparticle vaccines showed a Th2 response bias and steady sustainment of antigen specific antibody titers with high avidity while an equivalent soluble antigen dose showed no response. Antigen specific recall responses were measured twelve weeks post immunizations and microparticle vaccine groups showed a robust serological antibody response not seen in soluble antigen vaccinated groups. These humoral responses suggest that the delayed release of antigen allows a maturing immunological response with antigen specific recall. These studies have important implications for the rational design of single dose vaccines with dose sparing capabilities.