Construction of an infectious cDNA clone of foot-and-mouth disease virus type O 1 BFS 1860 and its use in the preparation of candidate vaccine.

Foot-and-mouth disease virus (FMDV) serotype O is the most predominant among the endemic serotypes in India. A stable,full-length cDNA clone of FMDV type O 1 BFS 1860 preceded by a bacteriophage T7 polymerase promoter was assembled in a plasmid vector pGEM R- - 7Zf(-). An 8.2 kb PCR product was amplified from the cDNA clone and a full-length RNA was generated from it by in vitro transcription.Transfection of BHK-21 cells with the in vitro transcripts resulted in the production of infectious recombinant FMDV particles as evidenced by cytopathic effects (CPE). Further, characterization of the recombinant virus by immunofluorescence, microneutralization test (MNT), antigen ELISA,RT-PCR, plaque assay and electron microscopy revealed similarity to the parental strain. The immunogenicity of an oil-adjuvant vaccine prepared using the inactivated recombinant virus was tested in guinea pigs and cattle. Neutralizing antibodies were produced in both vaccinated guinea pigs and cattle. Vaccinated animals were protected on challenge. The results demonstrated that the recombinant virus was as stable and effective as the parental strain for the preparation of inactivated vaccine, suggesting the potential application of this strategy to make genetically engineered FMDV vaccines.