Immunogenicity of the epitope of the foot-and-mouth disease virus fused with a hepatitis B core protein as expressed in transgenic tobacco

A novel plant-based vaccine protecting against foot-and-mouth disease (FMD) was developed by inserting the VP21 epitope into the internal region of the hepatitis B virus core antigen gene (HBcAg). The specific sequence of the VP21 epitope is located within the VP1 capsid protein of the FMD virus (FMDV). It spans 21 amino acids located between positions 140 and 160 of the G-H loop. The fusion gene, HBCVP, was inserted into the plant binary vector pBI121 and then transformed into tobacco (Nicotiana tabacum) plants via Agrobacterium tumefaciens strain LBA 4404. The presence of HBCVP in the tobacco genome was confirmed by polymerase chain reaction (PCR); its transcription was verified by reverse transcription-PCR; and the recombinant protein expression was confirmed by Western blot analysis. The results of immunologic microscopic observation demonstrated that recombinant fusion protein HBCVP can form a virus-like particle (VLP) structure in transgenic tobacco leaves. Mice, immunized intraperitoneally with a soluble crude extract of transgenic tobacco leaves, were found to produce specific antibody responses to both HBcAg and FMDV VP1. A virus challenge demonstrated that the immunized mice were highly protected against virulent FMD. This work describes a new way to develop an FMD vaccine from plants that will aid the development of new vaccines using HBcAg fused to the conserved epitopes of other pathogenic antigens.