Screening Natural Compounds With Antiviral Activities Against Porcine Reproductive And Respiratory Syndrome Virus (PRRSV) And Investigating Their Antiviral Mechanisms

Objectives:To screen the antiviral activities of twenty natural compounds extracted from traditional Chinese medicines (TCMs) on porcine reproductive and respiratory virus (PRRSV) in vitro and explore their antiviral mechanisms.Methods:Visualization of cytopathologic effect (CPE) assay and3-(4,5-dimethyithiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test were used to determine maximum no-cytotoxic concentration (MNTC),50%cytotoxic concentration (CC50),50%effective concentration (EC50) and maximum inhibition ratio (MIR) on Marc-145cell. The antiviral mechanisms of the screened compounds, which possessed both SI value was larger than3and MIR was higher than50%, were investigated through time-of-addition assay, adsorption inhibition assay and virucidal assay. In addition, Annexin V/PI double staining and the expression of caspase-3detected by Western blot were used to determine the effect of natural compounds on PRRSV-induced apoptosis.Results:Three of the twenty compounds, Dipotassium Glycyrrhizinate (DG), Matrine (MT) and Sodium Tanshinone IIA sulfonate (STS), showed potent anti-PRRSV activity. Selectivity index (SI) value of DG, MT and STS was>16.6,>3.8and>10.9, respectively, and all the inhibition ratioswere over90%. The inhibition ratios of DG, MT and STS were higher than70%in viral replication cycle (1-14h), and higher than90%in virucidal assay. In addition, the number of late apoptotic cells respectively in DG, MT and STS treated group marked decreased, compared with PRRSV control. And the activation caspase-3was undetectable both in DG and MT group.Conclusions:DG, MT and STS inhibited PRRSV via persistent inhibiting PRRSV replication, directly inactivating PRRSV and disturbing PRRSV-induced apoptosis.