Transgenic Soybeans as a Platform Technology to Develop Pharmaceuticals.

We have been developing a platform technology utilizing transgenic soybeans as a host to produce safe and efficacious vaccines that are (1) economically-friendly, (2) stable for long periods of time (years), (3) stored and transported without the requirement for a cold chain, and (4) easily processed into formulations that are practical for oral delivery.  To demonstrate this technology, we recently performed proof-of-concept experiments to determine whether a detoxified Staphylococcal enterotoxin B (SEB) antigen could be expressed in soybeans and formulated into a practical vaccine that could be administered orally and confer protection following lethal challenge with native SEB toxin.  To this end, we optimized and constructed a synthetic detoxified SEB gene for expression as a vaccine antigen in soybean.  Under the direction of a seed storage protein promoter, we found that transgenic SEB accumulated to levels representing >3% of the total soluble seed protein.  The soy-derived antigen was immunogenic when administered to mice, as systemic and mucosal immune responses were detected as measured by serum and fecal anti-SEB antibody titers and cytokine release in restimulation assays.  To test the efficacy of the soy-derived vaccine, control and vaccinated groups of mice were challenged with a lethal dose (5LD₅₀) of native toxin and monitored for one week.  All animals vaccinated with soy-derived SEB survived the lethal challenge while none of the control animals survived challenge.  Our proof-of-concept studies clearly demonstrate that the expression of pharmaceutical proteins in soybeans is indeed a viable platform for the future development of safe and efficacious vaccines.