In developing countries, oral immunization is more readily accepted than parenteral, as it accompanies the ease and safety of administration and induces the desired mucosal immune response against highly infectious pathogen transmitted through mucosal routes. Despite the obvious need and apparent merits, the success in the field of oral vaccination is limited due to factors including harsh gastric environment, enzymatic barrier, intestinal epithelium barrier and the fear of oral tolerance reported in case of mucosal vaccination. The number of strategies has been focused at conquering the mucosal barrier for maximization of the intestinal uptake and stabilization of the biological at all stages before they reach their target. Although, considerable success has been attained using these strategies but none of these have achieved commercial status. Therefore a rationally designed oral vaccine should be successfully delivered to the intestinal mucosal immune cells, and induce both humoral and cellular counterparts of immunity along with the mucosal immune response. The aim of this review article is to describe the recent development in the understanding of the molecular mechanism and implication of gastrointestinal epithelium and cytokines interplay in the induction of immunity and tolerance. The review has been elaborated to discuss the rationale of design of suitable carrier in conjunction with the peculiar necessities of gastrointestinal tract for induction of well balanced immune response.
Keywords: Oral vaccines, gut immunology, tolerance, antigen delivery systems, targeting
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