Induction of a virus-specific antibody response to foot and mouth disease virus using the structural protein VP1 expressed in transgenic potato plants

We have recently communicated the oral and parental immunogenicity of the s tructural protein VP1 of foot and mouth disease virus (FMDV) expressed in d ifferent transgenic plants. Those results clearly indicated the necessity o f increasing the expression of the foreign genes in the transgenic plant to avoid additional steps toward the purification and/or concentration of the antigen of interest. Here, we report the production of transgenic potatoes plants containing the VP1 gene cloned under the regulatory activity of eit her a single (pRok2) or a double (pRok3) copy of the S35 cauliflower mosaic virus (CaMV 35S) promoter, as a strategy for increasing the level of VP1 g ene expression. The presence of the VP1 gene in the plants was confirmed by polymerase chain reaction (PCR) and its specific transcription activity wa s demonstrated by reverse transcriptase-polymerase chain reaction (RT-PCR), The results showed that, although the immunized animals presented a FMDV V P1 specific antibody response and protection against the experimental chall enge, no significant differences were demonstrated in the immunizing activi ty of plant extracts obtained from the pRok2 or pRok3 transformed plants, T hese results confirm those previously obtained using other plant species al lowing the possibility of using plants as antigen expression vectors, and d emonstrated that at least in the potato system, the use of double CaMV 35S promoter does not cause a significant increase in the level of the VP1 expr essed.