Inhibition of replication of classical swine fever virus in a stable cell line by the viral capsid and Staphylococcus aureus nuclease fusion protein

Classical swine fever (CSF) is one of the major diseases causing serious economic losses to the swine industry. To explore the feasibility of using capsid-targeted viral inactivation (CTVI) as an antiviral strategy against CSF infection, a plasmid pcDNA–Cap–SNase was constructed for expressing a fusion protein of CSFV capsid (Cap) and Staphylococcus aureus nuclease (SNase). Under G418 selection, a mammalian cell line PK-15 expressing stably the fusion protein Cap–SNase(PK-15/Cap–SNase) could be detected by rabbit antiserum against CSFV capsid protein and had good nuclease activity in cleaving linearized plasmid DNA. The CSFV titer produced from infection of this PK-15/Cap–SNase stable cell line was reduced by an order of 102–103.5 or 70.8% compared to that produced in control PK-15 cells. Detection of the virus by ELISA indicated that CSFV propagation was inhibited in the PK-15/Cap–SNase cell line. It was demonstrated clearly that the fusion protein Cap–SNase could inhibit effectively the production of CSFV, resulting in a reduction in infectious titers. Therefore, CTVI may be valuable therapeutic approach against CSFV.