Immunogenicity of Fusion Protein of Cholera Toxin B Subunit-Porphyromonas gingivalis 53-kDa Minor Fimbrial Protein Produced in Nicotiana benthamiana

Porphyromonas gingivalis induces destruction of periodontal tissues that surround and support the teeth, contributing to the development of periodontitis, which eventually results in tooth loss in adults. A 53-kDa protein of P. gingivalis is a major subunit variant protein of minor fimbriae (Mfa1), and is reported to be highly immunogenic and considered as a potential vaccine candidate. The gene encoding 53-kDa protein, was divided into three segments, and each DNA segment was fused to the gene coding for cholera toxin B subunit (CTB) to improve gut mucosal immune responses. The ctb-mfal fusion genes were expressed in the leaf tissues of Nicotiana benthamiana using agroinfiltration. Immunoblot analysis revealed that CTB-Mfa1 fusion proteins were produced in the agroinfiltrated leaves. The interaction of the plant-produced CTB-Mfa1 fusion proteins with G_M1-ganglioside, which acts as the binding site for native CTB, was confirmed by G_M1-ELISA. Mice immunized orally with the agroinfiltrated leaf powder containing the CTB-Mfa1 fusion proteins elicited serum IgG and fecal IgA antibodies to CTB and Mfa1. These results suggest that CTB-Mfa1 fusion proteins produced in plants can be used as an oral vaccine to control P. gingivalis infection-associated periodontitis.