Targeting Cellular Receptors as a Strategy for the Development of New Generation Mucosal Vaccines

Mucosal pathogens are a primary source of infection that require the development of vaccines to induce a specific, protective and long lasting immune response. Despite an urgent need, development of effective mucosal immunization strategies has proven difficult. The literature was reviewed to elucidate cell specific targets that may be utilized to increase the immunogenicity of protective antigens through mucosal vaccination. Vaccine vehicles such as liposomes, outer membrane vesicles and Poly Lactic Acid (PLA) nanoparticles serve as antigen delivery systems as well as immuno-stimulatory agents. Even with the advances in mucosal vaccine delivery mechanisms many systems lack specificity and fail to generate a protective immune response. Hence, targeting extracellular receptors by harnessing antibody specificities, bacterial molecules, or toxins in conjunction with protective antigens provides an attractive alternative to conventional vaccine regiments that may circumvent the need for delivery systems and adjuvants. Fusion proteins targeting M cells, dendritic cells, or lymphocytes, are promising candidates for enhancing antigenic trafficking across the mucosal membrane and subsequent uptake by antigen presenting cells. Directing antigens to extracellular receptors of epithelial and immune cells via mucosal immunization provides an attractive model for generating a protective memory immune response that is essential to a successful vaccine regiment.