Exploiting receptor biology for oral vaccination with biodegradable particulates

The effective delivery of antigens via the oral route is an extremely desirable goal. Mucosal delivery of antigens stimulates mucosal and systemic immunity without affecting maternal antibodies and reduces the need for sterile needles or trained personnel. To date, there are very few commercially available oral vaccines and despite numerous reports in the scientific literature to show the success of biodegradable antigen carriers, none of these have achieved commercial status. Nevertheless, many studies have shown the great potential of biodegradable antigen carriers for oral vaccination in preclinical studies, but a more rational approach may be to specifically target antigen-loaded biodegradable microspheres to cells in the mucosal immune system which transport and process antigens for T cell recognition. Modern cell and molecular biology techniques have unearthed a wealth of information regarding important receptors involved in the capture of luminal antigens by microfold or membranous (M) cells and receptors on dendritic cells (DCs) which may allow future targeting of antigens to specific DC phenotypes, thus directing the immune response appropriately. In this review, we consider the use of currently available biodegradable antigen carriers and speculate on how these may be improved to more efficiently target mucosal effector sites.