Cloning and expression of FMDV-VP1 immunoreactive peptide in trivalent form and its application as immunogen

A search for alternatives to conventional inactivated virus vaccine for FMD with an aim to control and eradicate the disease globally, is a continuous process till a promising one is identified. Development of such vaccines underlines necessity of avoiding the use of active virus, and to have broader antigenic coverage so as to make them suitable even for disease free countries. Subunit or peptide vaccines have been shown to elicit neutralizing antibody response. However, the titres are low as compared to sera from animals vaccinated with conventional vaccine and fail to protect animals against virus challenge. This is probably due to the inclusion of only limited epitopes. Under such conditions, mixing heterologous epitopes from the various serotypes may be a better approach for elicitation of high titred antibody response. Keeping this in view, we have linked C-terminal half of VP1 carrying two B cell and one T cell epitope of three FMDV serotypes (O, A and Asia 1), which are presently in use as vaccine strains in India. The linked polyvalent gene was expressed in Escherichia coli and the 59 kDa fusion protein was studied for its immunogenicity in guinea pigs in comparison with the specific epitopes of type ‘O’ produced as a similar fusion protein of 30 kDa. The trivalent protein showed better neutralizing antibody response, even with single booster injection, as compared to monovalent protein as observed in ELISA and SNT. These studies show future scope for the development of protein/DNA-based vaccine for FMD.