Protection of mice against challenge with foot and mouth disease virus (FMDV) by immunization with foliar extracts from plants infected with recombinant tobacco mosaic virus expressing the FMDV structural protein VP1.

A tobacco mosaic virus (TMV)-based vector has been used to express in plants the complete open reading frame coding for VP1, the major immunogenic protein of foot and mouth disease virus (FMDV). In vitro RNA transcripts were inoculated into Nicotiana benthamiana plants and detectable amounts of recombinant VP1 were identified by Western blot as soon as 4 days postinfection. Foliar extracts prepared from infected leaves were injected intraperitoneally into mice and all of the immunized animals developed a specific antibody response to both the complete virus particle and the major immunogenic region as determined by ELISA and Western blot analysis. Most importantly, all immunized mice developed a protective immune response against experimental challenge with virulent FMDV. To our knowledge, this is the first report showing the expression of a complete open reading frame of an antigenic foreign protein in plants, using a recombinant plant virus, in sufficient quantity to permit use of the crude plant extract as an experimental immunogen to protect animals against virus challenge. Copyright 1999 Academic Press.