Induction of a protective antibody response to foot and mouth disease virus in mice following oral or parenteral immunization with alfalfa transgenicplants expressing the viral structural protein VP1

The utilization of transgenic plants expressing recombinant antigens to be used in the formulation of experimental immunogens has been recently commun icated. We report here the development of transgenic plants of alfalfa expr essing the structural protein VP1 of foot and mouth disease virus (FM DV). The presence of the transgenes in the plants was confirmed by PCR and their specific transcription was demonstrated by RT-PCR. Mice parenterally immun ized using leaf extracts or receiving in their diet freshly harvested leave s from the transgenic plants developed a virus-specific immune response. An imals immunized by either method elicited a specific antibody response to a synthetic peptide representing amino acid residues 135-160 of VP1, to the structural protein VP1, and to intact FMDV particles. Additionally, the imm unized mice were protected against experimental challenge with the virus. W e believe this is the first report demonstrating the induction of a protect ive systemic antibody response in animals fed transgenic plants expressing a viral antigen. These results support the feasibility of producing edible vaccines in transgenic forage plants, such as alfalfa, commonly used in the diet of domestic animals even for those antigens for which a systemic immu ne response is required. (C) 1999 Academic Press.