Patent ID: 8133495

Claim:
A recombinant classical swine virus (CSFV) mutant comprising a DNA sequence encoding a mutation in the E1 glycoprotein of said CSFV mutant, wherein the mutation comprises a 20 mer insertion (SEQ ID NO: 9) at nucleotide position 2429, wherein said 20 mer insertion comprises the FLAG™ epitope in the E1 glycoprotein of the CSFV mutant, said epitope consisting of the amino acid sequence, DYDDDDK (SEQ ID NO: 5) as the last eight amino acids of the insertion, wherein said recombinant CSFV mutant is a live attenuated CSFV and said FLAG™ epitope carried by said CSVF mutant is capable of being recognized by monoclonal antibodies specifically binding to said FLAG™ epitope, which serve as a positive mutation marker for said live attenuated CSFV mutant.