High level expression of a functionally active cholera toxin B: rabies glycoprotein fusion protein in tobacco seeds

A synthetic DNA construct containing cholera toxin B subunit, genetically fused to the surface glycoprotein of rabies virus was expressed in tobacco plants from a seed specific (legumin) promoter. Seed specific expression was monitored by real-time PCR, GM1-ELISA and Western blot analyses. The fusion protein accumulated in tobacco seeds at up to 1.22% of the total seed protein. It was functionally active in binding to the GM1-ganglioside receptors, suggesting its assembly into pentamers in seeds of the transgenic plants. Immunoblot analysis confirmed that the ~80.6 kDa monomeric fusion polypeptide was expressed in tobacco seeds and accumulated as a ~403 kDa pentamer. Evaluation of its immunoprotective ability against rabies and cholera is to be examined.