Porcine circovirus genotype 2a (PCV2a) and genotype 2b (PCV2b) recombinant mutants showed significantly enhanced viral replication and altered antigenicity in vitro

Two recombinant mutants of porcine circovirus type 2 (PCV2), which resulted from replacement of a genomic fragment containing the open reading frame 2 (ORF2) of genotype PCV2b with that of genotype PCV2a, were obtained initially from co-infection with PCV2a and 2b genotype viruses in vitro. The two mutant viruses contained the ORF1 sequence from genotype PCV2b and the ORF2 sequence from genotype PCV2a. They were designated according to the nomenclature proposed by Grau et al., indicating the origin of the ORF1 sequence first and that of the ORF2 sequence second, i.e., PCV2b(JF11)/2a(CL1) and PCV2b(YJ)/2a(CL1). The replication efficiencies of the two PCV2 recombinant mutants were enhanced significantly and their antigenicities were altered significantly in vitro when compared with their parental strains.