Zonula occludens toxin is a powerful mucosal adjuvant for intranasally delivered antigens

Zonula occludens toxin (Zot) is produced, by toxigenic strains of Vibrio ch olerae and has the ability to reversibly alter intestinal epithelial tight junctions, allowing the passage of macromolecules through the mucosal barri er. In the present study, we investigated whether Zot could be exploited to deliver soluble antigens through the nasal mucosa for the induction of ant igen-specific systemic and mucosal immune responses. Intranasal immunizatio n of mice with ovalbumin (Ova) and recombinant Zot, either fused to the mal tose-binding protein (MBP-Zot) or with a hexahistidine tag (His-Zot), induc ed anti-Ova serum immunoglobulin G (IgG) titers that were approximately 40- fold higher than those Induced by immunization with antigen alone. Interest ingly, Zot also stimulated high anti-Ova IgA titers in serum, as well as in vaginal and intestinal secretions. A comparison with Escherichia call heat -labile enterotoxin (LT) revealed that the adjuvant activity of Zot was onl y sevenfold lower than that of LT, Moreover, Zot and LT induced similar pat terns of Ova-specific Ige subclasses. The subtypes IgG1, IgG2a, and IgG2b w ere all stimulated, with a predominance of and IgG2b, In conclusion, our re sults highlight Zot as a novel potent mucosal adjuvant of microbial origin.