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 10(2)-10(3.5) 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.
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