Rescue of porcine circovirus type 2 from cloned DNA

: Infectious clone is a useful tool in exploring viral replication and pathogenesis. In order to prevent linear PCV2 cyclization, PCR mutagenesis was used to construct the first molecular clone (pSK-2PCV2) by ligating two copies of the complete PCV2 genome with the pBluescript SK (pSK) vector. In addition, pSK-PCV2 and ds-PCV2 were constructed. PK-15 cells were transfected with above three infectious clones. Indirect immunofluorescence assay (IFA) revealed that the virus antigen mainly localized in infected cell nucleolus and cytoplasm. PCV2 specific nucleotide fragment in cell culture was amplified by RT-PCR. Typical porcine circovirus particles with diameter about 17 nm were also observed by transmission electron microscope (TEM) in the infected cells. The rescued virus sequences from the cultures had 100% homology with the inserting PCV2 genome. The rescued virus shared similar properties with that of the parental virus. The study establishes a platform for further research on the virus molecular biology and pathogenicity.