A recombinant truncated FMDV 3AB protein used to better distinguish between infected and vaccinated cattle

To distinguish the antibodies induced by Foot-and-mouth disease virus (FMDV) infection from those induced by vaccination, a recombinant N-terminal truncated FMDV non-structural protein (NSP) of 3AB, designated as r3aB, was constructed by deleting 80 amino acids displayed about 30% homology to transposase IS4 family protein of Escherichia coli, expressed in E. coli BL21 (DE3) and then purified. The r3aB was majorly expressed in soluble fraction and presented as homogeneous monomers after purification. Using r3aB as coating antigen, an indirect ELISA was established to specifically identify antibodies induced by FMDV infection but not those induced by vaccination. Compared with 3AB, r3aB was more specific to catch antibodies against NSP. The performance of this assay was validated by two commercial FMDV NSP ELISA kits. The result suggested that the r3aB coated ELISA could be developed into a kit to better distinguish between infected and vaccinated cattle.