A number of antigenic non-structural proteins (NSPs) of FMD were identified and out of which 3ABC gene appears to be the most reliable marker of FMD virus replication [196, 197] . The deletion of NSP (3ABC) gene has been used for enabling DIVA approach for FMD (Cedivac-FMD inactivated vaccine). For detection of NSP antibodies, the Ceditest FMD-NS ELISA is commercially available. Indirect ELISA test for the detection of antibodies against nonstructural proteins will play an essential role in the serological survey of livestock herds in future postoutbreak situations. It has been demonstrated that protection against footand-mouth disease (FMD) could be achieved following vaccination with chimeric foot-and-mouth disease virus (FMDV) vaccines, in which the VP1 G-H loop had been substituted with that from another serotype. This indicated that the VP1 G-H loop may not be essential for the protection of natural hosts against FMDV. If this could be substantiated there would be potential to develop FMD marker vaccines, characterised by the absence of this region [198] . A mutant FMDV with deletion of immunodominant epitopes was evaluated to use as a marker vaccine recently, In that study, a B-cell epitope was identified in the 3A region of a nonstructural protein (NSP) by anti-FMDV cattle sera and a recombinant FMDV (rvAs-3A14D) was generated by selectively deleting 14 amino acids (position [91] [92] [93] [94] [95] [96] [97] [98] [99] [100] [101] [102] [103] [104] in the 3A region of the NSP. Following in vitro transcription and transfection in BHK-21 cells, the rvAs-3A14D was rescued from BHK-21 cells. Characterization of the rvAs-3A14D revealed that the infectivity, antigenecity, and replication kinetics in BHK21 cells and virulence in mice of the rvAs-3A14D were similar to that of its parent virus. Those data 8 Veterinary Medicine International suggested that the recombinant FMDV with deletion of this epitope in the NSP may be potentially used as a candidate inactivated vaccine and therefore, the application of the marker vaccine and differential diagnostic tests may open a promising new avenue for the development of a vaccine for DIVA.