Fig. 1. Characterization of a type O FMD vaccine strain, O JC-R virus. (A) Schematic diagram of the type O JC-R FMDV genome; the 3B₁B₂ replacement was performed by using the method given by Ko et al. [11] and the 142 residue (C142T) in the 3C region was mutated. (B) Electron microscopy of the FMDV vaccine strain, O JC-R. The bar represents 100 nm. (C) Pathogenesis of O JC-R and O JC wild-type (O/Jincheon/SKR/2014) or mutated viruses in 7-days-old mice. (D) No detection of the NSP antigen in virus cultured supernatant when using the FMDV antigen rapid kit (PBM, USA) for differentiation between vaccine and wild-type virus using the previous method [11].

C, control line; SP, FMDV structural protein line; NSP, FMDV non-structural protein line; FMD, foot-and-mouth disease; FMDV, foot-and-mouth disease virus.