Oral delivery of tetanus toxoid using vesicles containing bile salts (bilosomes) induces significant systemic and mucosal immunity

Protein antigens administered via the oral route are exposed to a hostile environment in the gastrointestinal tract, consisting of digestive enzymes and a range of pH (1-7.5). Using a delivery system can afford protection to entrapped components against degradation and permit delivery of antigen to the cells responsible for generating local and systemic immune responses. In this comparative study, mice were immunised orally with tetanus toxoid (40 or 200 microg dose/mouse, four doses in total) entrapped in non-ionic surfactant vesicles formulated with bile salts (bilosomes). The higher entrapped dose (BV-TT, 200 microg) induced IgG1 by study week 3 to similar levels to those observed with subcutaneous un-entrapped TT at the lower (<50 microg) dose. However, both bilosome formulations (BV-TT, low, and high doses), though not un-entrapped TT, caused a rise in the numbers of IgA positive plasma cells observed in the small intestine, primarily in the first 15 cm of the small intestine.