Abstract Porcine circovirus type 2 (PCV2), the essential causative agent of PCV2-associated disease (PCVAD), has made a grave threat to the worldwide swine industry, but no efficacious therapy has been found to treat this viral infection. To explore a new approach to treat PCVAD, plasmids (pGensil-R259, pGensil-C297 and pGensil-C490) encoding siRNA to PCV2 replication-involved (rep) and capsid (cap) protein genes, which encode virus Rep protein and Cap protein respectively, were constructed with a plasmid (pGensil-SCR) encoding PCV2-nonspecific siRNA as a negative control. PK-15 cells were respectively transfected with different PCV2-specific siRNA expression plasimids and negative plasmids by liposome and these cells were inoculated with PCV2 at 20 h of post-transfection. Plasmid-based PCV2-specific siRNA significantly inhibited DNA synthesis, Rep and Cap protein expression of PCV2 and reduced virus titers markedly. The inhibition changed along with different positions in siRNA target gene sequences. Within 36 h post-infection, PCV2-specific siRNA conducted the strongest inhibition and it could significantly inhibited PCV2 replication until 60 h post-infection in spite of a slight decline. These results showed that plasmid-based specific siRNA can strongly inhibit PCV2 replication while the inhibition is in negative correlation with action time.
