Viral DNA from Cells Infected with Porcine Circovirus

It has been demonstrated earlier that the genome of the porcine circovirus (PCV) isolated from virions is a circular single-stranded DNA (ssDNA). This report describes the isolation and characterization of PCV-specific DNA from infected cell cultures. Two types of doublestranded DNA (dsDNA) were observed which behaved like supercoiled and relaxed circular molecules, respectively. Both types of dsDNA displayed infectivity in transfection experiments and are regarded as replicative forms (RF) of the viral genome. In addition to complete single-stranded viral genomes and RF DNA molecules, PCV-specific subgenomic fractions of DNA molecules with a sedimentation coefficient of about 5 S were isolated from infected tissue culture cells. This 5 S DNA was also isolated from purified virions. It is single-stranded and represents a defined region of the viral genome.