Induction of protective immunity in swine by recombinant bamboo mosaic virus expressing foot-and-mouth disease virus epitopes

Background: Plant viruses can be employed as versatile vectors for the production of vaccines by expressing immunogenic epitopes on the surface of chimeric viral particles. Although several viruses, including tobacco mosaic virus, potato virus X and cowpea mosaic virus, have been developed as vectors, we aimed to develop a new viral vaccine delivery system, a bamboo mosaic virus ( BaMV), that would carry larger transgene loads, and generate better immunity in the target animals with fewer adverse environmental effects. Methods: We engineered the BaMV as a vaccine vector expressing the antigenic epitope(s) of the capsid protein VPI of foot-and-mouth disease virus ( FMDV). The recombinant BaMV plasmid (pBVPI) was constructed by replacing DNA encoding the 35 N-terminal amino acid residues of the BaMV coat protein with that encoding 37 amino acid residues (T-128-N-164) of FMDV VPI. Results: The pBVPI was able to infect host plants and to generate a chimeric virion BVPI expressing VPI epitopes in its coat protein. Inoculation of swine with BVPI virions resulted in the production of anti-FMDV neutralizing antibodies. Real-time PCR analysis of peripheral blood mononuclear cells from the BVPI-immunized swine revealed that they produced VPI-specific IFN-gamma. Furthermore, all BVPI- immunized swine were protected against FMDV challenge. Conclusion: Chimeric BaMV virions that express partial sequence of FMDV VPI can effectively induce not only humoral and cell-mediated immune responses but also full protection against FMDV in target animals. This BaMV-based vector technology may be applied to other vaccines that require correct expression of antigens on chimeric viral particles.