Charged polylactide co-glycolide microparticles as antigen delivery systems

Polymeric microparticles with encapsulated antigens have become well-established in the last decade as potent antigen delivery systems and adjuvants, with experience being reported from many groups. However, the authors have recently shown that an alternative approach involving charged polylactide co-glycolide (PLG) microparticles with surface adsorbed antigen(s) can also be used to deliver antigen into antigen-presenting cell populations. The authors have described the preparation of cationic and anionic PLG microparticles that have been used to adsorb a variety of agents, to include plasmid DNA, recombinant proteins and adjuvant active oligonucleotides. These novel PLG microparticles were prepared using a w/o/w solvent evaporation process in the presence of the anionic surfactants, such as dioctyl sodium sulfosuccinate, or cationic surfactants, such as hexadecyl trimethyl ammonium bromide. Antigen binding to the charged PLG microparticles was influenced by both electrostatic interaction and other mechanisms, including hydrophobic interactions. Adsorption of antigens to microparticles resulted in the induction of significantly enhanced immune responses in comparison with alternative approaches. The surface adsorbed microparticle formulation offers an alternative way of delivering antigens as a vaccine formulation.