Coadministration of protoxin C ry1 A c from B acillus thuringiensis with metacestode extract confers protective immunity to murine cysticercosis

Summary The B acillus thuringiensis C ry1 A c protoxin (p C ry1 A c) is a promising mucosal immunogen and adjuvant that induces protective immunity against N aegleria fowleri and malaria infection models. We determined whether p C ry1 A c acted as a protective adjuvant against infection with T aenia crassiceps . BALB / C mice were thrice i.p. immunized with (i) p C ry1 A c, (ii) metacestode extract, (iii) extract + p C ry1 A c or (iv) vehicle, challenged with metacestodes on day 26 and then sacrificed 35 days later. Cysticerci in the peritoneal cavity were counted, while the serum antibody response and cytokines were analysed after immunization and during infection. Only immunization with p C ry1 A c plus extract conferred a significant protection (up to 47%). This group presented fluctuating antibody peaks during infection and the highest I g G 1 and I g M titres. Immunization with extract alone elicited high I g G 1 and the highest I g G 2a responses after 25 days of infection, while nonimmunized mice presented a poor, mixed‐ T h1/ T h2 response during infection. Sharp peaks of TNF α and IFN ‐γ occurred immediately after the first immunization with extract, especially in the presence of p C ry1 A c, but not after the challenge, while in the control and p C ry1 A c‐alone groups, cytokines were only detected after the challenge. The data support the protective‐adjuvant effect of co‐administration of p C ry1 A c in cysticercosis.