Antiviral Drug Screening Against Swine Acute Diarrhea Syndrome Coronavirus

Swine acute diarrhea syndrome coronavirus（SADS-CoV）,an alphacoronavirus discovered in Guangdong province of China in 2017,has continuously spread to southern China and caused a large scale of swine diarrheal outbreaks,resulting in massive piglet deaths and severe economic losses to the local pig farming.No approved drug or vaccine is now available against the infection.In this study,SADS-CoV infection on the human hepatoma cell line Huh7 was tested,and q PCR and TCID50 assays were conducted to measure the content of viral RNA and viral titer in the supernatant to determine SADS-CoV growth curve,which was applied as an infection model for drug screening.Based on the strategy of old drug repurposing,antivirals screening against SADS-CoV from an approved-drug library containing 2080 compounds,was first performed.Through the test of half inhibitory concentration and cytotoxicity,four compounds significantly exhibited inhibitory effects on SADS-CoV infection,namely gemcitabine,mycophenolate mofetil,mycophenolic acid and methylene blue.Further validations,including time-of-addition assay,q PCR,western blot and plaque assay,confirmed that methylene blue effectively inhibited the whole infection procedure,while gemcitabine,mycophenolate mofetil and mycophenolic acid mainly inhibited the post-entry phase of the virus.Adsorption and internalization results showed that methylene blue could inhibit virus binding,and methylene blue,gemcitabine,mycophenolate mofetil and mycophenolic acid were found to inhibit virus proliferation through the investigation of virus growth affected with compound addition after viral entry.In addition,these four compounds were also determined for antiviral effects on porcine epidemic diarrhea virus（PEDV）infection through IC₅₀tests.In conclusion,it has found four potential compounds against SADS-CoV and PEDV infection through drug screening in this study,providing potential antiviral drugs and treatments for the outbreak of SADS-CoV or PEDV infection in the future.