Immunogenicity of foot-and-mouth disease virus structural polyprotein P1 expressed in transgenic rice

Transgenic plants have become developed as bioreactors for producing heterologous proteins and may even form edible vaccines. In the present study, a transgenic rice expressing the capsid precursor polypeptide (P1) gene of foot-and-mouth disease virus (FMDV), under the control of a dual cauliflower mosaic virus (CaMV 35S) promoter, was generated by Agrobacterium-mediated transformation. Southern blot, northern blot, western blot, and ELISA analyses confirmed that the P1 gene was integrated into the transgenic rice and the protein was expressed specifically in the leaves at levels of 0.6-1.3 μg/mg of total soluble protein. After intraperitoneal immunization of mice with crude protein extracts from transgenic rice plants, FMDV-specific neutralizing antibodies were detected. The immunized mice could clear virus from their sera after FMDV challenge. In addition, FMDV-specific mucosal immune responses were detected in mice after oral immunization with protein extracts from transgenic rice plants. Partial virus clearance was obtained after FMDV challenge. These results indicate the potential of using a transgenic rice-based expression system as an alternative bioreactor for FMDV subunit vaccines.