Cholera toxin B subunit conjugated bile salt stabilized vesicles (bilosomes) for oral immunization

Bile salt stabilized vesicles, bilosomes appear to be a promising and potential carrier system for oral delivery of peptides and proteins. Bilosomes containing bovine serum albumin (BSA), a model antigen, were prepared and conjugated with cholera toxin B subunit (CTB) in order to enhance their affinity towards M cells of Peyer's patches. Stability studies were undertaken to ascertain the effect of simulated gastric fluid (SGF, pH 1.2), simulated intestinal fluid (SIF, pH 7.5) and different concentrations of bile salts. Intactness and biological activity of CTB were checked by hemagglutination test. A single oral dose of CTB-conjugated bilosomes produced almost equivalent response compared to parenteral administration of antigen with Freund's complete adjuvant (FCA). However, in contrast to FCA, oral administration of bilosomes is convenient and devoid of any adverse effects that are observed with parenteral administration of FCA. Serum IgG titers after single administration were significantly better (P < 0.05) than oral administration of antigen with other systems for 3 consecutive days, suggesting an effective stimulation of systemic immune response. Mucosal IgA titers obtained advocated a possible application of CTB-conjugated bilosomes as oral vaccine delivery system.