Plant-made vaccines and reagents for the One Health initiative

Rybicki, Edward Peter

West Nile flavivirus (WNV)a mosquito-transmitted pathogen in the same family as Zika, yellow fever and Japanese encephalitis virusesis also of concern to One Health, given its recent intercontinental transmission from Europe to the Americas and the fact that the virus is transmitted regularly to livestock and to humans, and can cause severe disease. 39 A potentially useful vaccine candidate consisting of the domain III of the E glycoprotein was produced by ER-targetted transient expression in N benthamiana at levels of 73 mg/kg, and was easily purified, bound MAbs recognizing a conformational epitope of the native protein, and elicited a potent systemic immune response after subcutaneous immunization in mice. 40 Other work from the same group provided evidence that a humanised mAb to WNV E protein (E16) could be produced in N benthamiana by transient agroinfiltration-mediated expression, and that it protected mice against WNV-induced mortality comparably to mammalian-celL-produced E16 MAbs. 41 Later work demonstrated that both the WNV domain III (DIII) protein and the E16 mAb could be rapidly produced at high levels in plants and easily purified, and that they could be used to identify WNV, and detect human IgM responses to WNV infection, in serological assays. 42 The fact that E16 mAb does not cross-react with other flaviviruses makes it useful as a diagnostic, but also potentially useful in therapy, as it is not likely to cause antibody-dependent enhancement (ADE) of infection by other related flaviviruses such as yellow fever, Zika and dengue viruses.