Antigen uptake and immunoadjuvant activity of pathogen-mimetic hollow silica particles conjugated with β-glucan.

The aim of vaccines is to imitate the immune responses induced by pathogen infection without causing disease. Therefore, strategies of designing vaccine delivery systems by mimicking key features of pathogens are often used. For this purpose, the present study prepares pathogen-mimicking β-glucan-conjugated hollow silica particles by using polystyrene or bacteria particles as templates. The particles perfectly duplicate the structure and morphology of pathogens and possess excellent properties of hollow silica particles, including large opening pore channels, large interior cavities, high loading of OVA (ovalbumin) and controlled release capability, biocompatibility, tunability of surface functionality and immunopotentiating activity. In addition, the particles are antigen presenting cells (APCs) targeted by specific interaction with β-glucan specific receptors on the surface of APCs, which can enhance the uptake and sustained proteolytic processing of antigens and induce APC maturation. Eventually, potent Th1 and Th2-type immune responses are aroused. The size and shape of the particles have a significant impact on the antigen uptake and immunoadjuvant activity. The degree of antigen uptake enhancement is ranked in the following order: PS HSP@glucan (nanoscale spherical) > E. coli HSP@glucan (micron-sized rod-like) > S. aureus HSP@glucan (micron-sized spherical). The PS HSP@glucan is more apt to induce a Th1-type immune response, while the E. coli HSP@glucan is more apt to induce a Th2-type immune response. The particles may thus provide a promising strategy for development of novel vaccine delivery systems for inducing robust humoral and cellular immune responses against infectious diseases and cancers.