Plant-made vaccines and reagents for the One Health initiative

Rybicki, Edward Peter

Another innovative approach was the expression of a synthetic CCHFV envelope glycoprotein precursor (GcGn) polyprotein in leaves and induced hairy roots of transgenic tobacco plants: the material was immunogenic in mice via oral or parenteral immunisation routes, and GcGn purified from plants was an excellent ELISA plate coating antigen for detection of envelope glycoprotein-specific antibodies elicited by plantmade or conventional vaccines. 33 Rift Valley fever bunyavirus (RVFV) is a mosquito-transmitted pathogen of livestock that causes abortion storms in sheep and goats, and potentially lethal in humans, that is expanding its geographical range out of Africa into Arabia and elsewhere. 34 It is a matter of concern in the One Health movement because while there are effective veterinary vaccines, these are not necessarily safe, and there is no licensed human vaccine, 35 although experimental candidates that are safer in animals and may be suitable for humans, have been described. 36 A plant-made approach to a RVFV vaccine published recently described the expression in transgenic Arabidopsis thaliana of the N protein and a soluble version of the Gn glycoprotein. 37 Oral dosing of fresh transgenic plant material was immunogenic in mice, and elicited systemic antigen-specific IgG: this augurs well for similar experiments in larger animals. A spur to the deployment of human vaccines for RVFV could be the recent finding that the virus may be involved in human miscarriages in South Sudan. 38 Our laboratory is in the process of testing transiently-expressed RVFV N protein for its suitability as a diagnostic reagent, similar to the CCHFV case described above.