Micro/Nanoparticle Adjuvants: Preparation and Formulation with Antigens

Recombinant proteins are increasingly being used as a novel approach for antigens in vaccines. These genetically engineered antigens are poorly immunogenic and require a delivery system and adjuvant to elicit their effect at targeted site of action. A delivery system transports the antigen to site of action and an adjuvant activates the cells via interaction with cell receptors and enhances the potency of the antigen. Micro/nanoparticles made from biodegradable and biocompatible polyesters, polylactide-co-glycolides (PLG), have been extensively used as an adjuvant and delivery system. This chapter discusses the applications of PLG micro/nanoparticles as delivery systems and adjuvant for antigens. PLG microparticles are prepared by a solvent evaporation method while nanoparticles are prepared by solvent displacement method. Synthesis of PLG nanoparticles is simpler in comparison to microparticles and unlike microparticles, it also enables particles to be sterile filtered. In a direct comparison using mouse animal model, our group found that microparticles and nanoparticles exhibited similar immunogenic responses. Materials and methods for synthesis and characterization of micro/nanoparticles with adsorbed antigens are discussed in detail.