Suppression of porcine hemagglutinating encephalomyelitis virus replication by resveratrol

Background: Porcine hemagglutinating encephalomyelitis virus (PHEV), a member of the genus Betacoronavirus, is the causative agent of neurological disease in pigs. No effective therapeutics are currently available for PHEV infection. Resveratrol has been shown to exert neuroprotective and antiviral effects. Here resveratrol was investigated for its ability to inhibit PHEV replication in nerve cells and central nervous system tissues. Methods: Anti-PHEV effect of resveratrol was evaluated using an in vitro cell-based PHEV infection model and employing a mouse PHEV infection model. The collected cells or tissues were used for quantitative PCR analysis, western blot analysis, or indirect immunofluorescence assay. The supernatants were collected to quantify viral loads by TCID50 assay in vitro. EC50 and CC50 were determined by dose-response experiments, and the ratio (EC50/CC50) was used as a selectivity index (SI) to measure the antiviral versus cytotoxic activity. Results: Our results showed that resveratrol treatment reduced PHEV titer in a dose-dependent manner, with a 50% inhibition concentration of 6.24 mu M. A reduction of > 70% of viral protein expression and mRNA copy number and a 19-fold reduction of virus titer were achieved when infected cells were treated with 10 mu M resveratrol in a pre-treatment assay. Quantitative PCR analysis and TCID50 assay results revealed that the addition of 10 mu M resveratrol to cells after adsorption of PHEV significantly reduced 56% PHEV mRNA copy number and eightfold virus titer. 10 mu M resveratrol treatment reduced 46% PHEV mRNA copy number and fourfold virus titer in virus inactivation assay. Moreover, the in vivo data obtained in this work also demonstrated that resveratrol inhibited PHEV replication, and anti-PHEV activities of resveratrol treatment via intranasal installation displayed better than oral gavage. Conclusion: These results indicated that resveratrol exerted antiviral effects under various drug treatment and virus infection conditions in vitro and holds promise as a treatment for PHEV infection in vivo.