Oral Application of Recombinant Bacillus subtilis Spores to Dogs Results in a Humoral Response against Specific Echinococcus granulosus Paramyosin and Tropomyosin Antigens

is known as an endospore- and biofilm-forming bacterium with probiotic properties. We have recently developed a method for displaying heterologous proteins on the surface of biofilms by introducing the coding sequences of the protein of interest into the bacterial genome to generate a fusion protein linked to the C terminus of the biofilm matrix protein TasA. Although is a regular component of the gut microflora, we constructed a series of recombinant strains that were tested for their ability to be used to immunize dogs following oral application of the spores. Specifically, we tested recombinant spores of carrying either the fluorescent protein mCherry or else selected antigenic peptides (tropomyosin and paramyosin) from , a zoonotic intestinal tapeworm of dogs and other carnivores. The application of the recombinant spores led to the colonization of the gut with recombinant but did not cause any adverse effect on the health of the animals. As measured by enzyme-linked immunosorbent assay and immunoblotting, the dogs were able to develop a humoral immune response against mCherry as well as against antigenic peptides. Interestingly, the sera of dogs obtained after immunization with recombinant spores of peptides were able to recognize protoscoleces, which represent the infective form of the head of the tapeworms. These results represent an essential step toward the establishment of as an enteric vaccine agent.