Genetic and Antigenic Characterization of a Newly Emerging Porcine Circovirus Type 2b Mutant First Isolated in Cases of Vaccine Failure in Korea

This study describes the genetic and antigenic characterization of a newly emerging porcine circovirus type 2b (PCV2b) mutant first isolated in cases of vaccine failure in Korea. The full genome of the PCV2b isolates (SNUVR130689 and SNUVR140004) is 1,767 base pairs (bp) in length. The size of ORF1 is 945 bp, encoding a protein of 314 amino acids (aa), and the size of ORF2 is 705 bp, encoding a protein of 234 aa, which is 1 aa longer than that of the common PCV2 (233 aa). Korean PCV2b mutant strains had higher levels of nucleotide sequence identity to other PCV2b mutant strains (99.7-99.8 %) than to reference PCV2a (94.5-95.0 %) and PCV2b (95.5-96.1 %) strains. There was no difference in antigenic reactivity among PCV2a, PCV2b and PCV2b mutant strains to the polyclonal and monoclonal PCV2a antibodies. PCV2b mutant strains have distinct genetic characteristics but similar antigenic reactivity when compared to common PCV2a and 2b strains.