H. Suzuki1, J. Kunisawa2, 3, A. Watari1, M. Yamashita1, K. Yagi1 and M. Kondoh1
1Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, 565-0871, Japan; 2Laboratory of Vaccine Materials, National Institute of Biomedical Innovation, Osaka 567-0085, Japan; 3International Research and Development Center for Mucosal Vaccine, Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
Efficient delivery of antigen to mucosa-associated lymphoid tissues (MALT) is essential for mucosal vaccination. Claudin-4 (CL-4), a key structural and functional component of the tight junction, is expressed on the epithelial cells that cover MALT. We previously found that CL-4 targeting by using the C-terminal fragment of Clostridium perfringens enterotoxin (C-CPE) as a CL-4 binder is an effective strategy for the development of mucosal vaccines. Deletion of the 10 N-terminal amino acids of C-CPE increased its solubility, and substitution of Asn309 and Ser313 with Ala increased the affinity of C-CPE for CL-4. Here, we investigated whether a C-CPE mutant lacking the 10 terminal amino acids and carrying Ala309 and Ala313 could serve as a mucosal vaccine. We fused this Ala-substituted C-CPE mutant with ovalbumin (OVA) as a model antigen to generate the OVA-C-CPE mutant construct. Intranasal immunization with OVA-C-CPE mutant increased the production of OVA-specific serum IgG and mucosal IgA compared with that in mice immunized with OVA-C-CPE. In addition, immunization with OVA-C-CPE mutant activated both Th1 and Th2 responses and induced anti-tumor activity in mice inoculated with OVA-expressing thymoma cells. These findings suggest that the Ala-substituted C-CPE mutant is a promising CL-4 binder for claudin-targeted mucosal vaccination.