Generation of a recombinant classical swine fever virus stably expressing the firefly luciferase gene for quantitative antiviral assay

- A reporter CSFV was generated carrying the luciferase gene in the Npro gene.
- The luciferase activity was detectable as early as 4.5 h post-infection.
- The reporter virus allowed quantitative detection of the CSFV replication.
- The reporter virus enabled rapid detection of serum anti-CSFV neutralizing titers.
- The reporter virus enabled high-throughput screening of siRNAs against CSFV.

Classical swine fever (CSF), caused by classical swine fever virus (CSFV), is a highly contagious swine disease leading to significant economic losses worldwide. Vaccines are widely used to control the disease, and no CSFV-specific antivirals are currently available. To facilitate anti-CSFV molecule discovery, we developed a reporter virus CSFV-NproFluc stably expressing the firefly luciferase (Fluc) gene in the Npro gene. The reporter virus enabled more sensitive and convenient detection of the Npro protein expression and the viral replication by luciferase reporter assay than by traditional methods. The CSFV Npro protein was detectable as early as 4.5 h post-infection. As a proof-of-concept for its utility in rapid antiviral screening, this reporter virus was used to quantify anti-CSFV neutralizing antibodies of 50 swine sera and to assess 12 small interfering RNAs targeting different regions of the CSFV genome. The results were comparable to those obtained by traditional methods. Taken together, the reporter virus CSFV-NproFluc represents a useful tool for rapid and quantitative screening and evaluation of antivirals against CSFV.