Intragastric and intraperitoneal administration of Cry1Ac protoxin from Bacillus thuringiensis induces systemic and mucosal antibody responses in mice

The spore-forming soil bacterium Bacillus thuringiensis produces parasporal inclusion bodies composed by delta-endotoxins also known as Cry proteins, whose resistance to proteolysis, stability in highly alkaline pH and innocu ity to vertebrates make them an interesting candidate to carrier of relevan t epitopes in vaccines. The purpose of this study was to determine the muco sal and systemic immunogenicity in mice of CrylAc protoxin from B. thuringi ensis HD73. Crystalline and soluble forms of the protoxin were administered by intraperitoneal or intragastric route and anti-CrylAc antibodies of the major isotypes were determined in serum and intestinal fluids. The two for ms of CrylAc protoxin administered by intraperitoneal route induced a high systemic antibody response, however, only soluble CrylAc induced a mucosal response via intragastric. Serum antibody levels were higher than those ind uced by cholera toxin. Systemic immune responses were attained with doses o f soluble CrylAc ranging from 0.1 to 100 mu g by both routes, and the maxim al effect was obtained with the highest doses. High anti-CrylAc IgG antibod y levels were detected in the large and small intestine fluids from mice re ceiving the antigen via IF. These data indicate that CrylAc is a potent sys temic and mucosal immunogen.