Fig. 3

Effect of quercetin on SADS-CoV inactivation, adsorption, entry, and replication. (A) Virucidal assay. Different concentrations of quercetin were used to co-incubate with SADS-CoV (0.1 MOI) at 37 °C for 1 h, then diluted and inoculated in 96-well plates, and virus titers were measured by TCID50. (B) Virus prophylaxis assay. Different concentrations of quercetin were pretreated with IPI-FX for 1 h, and SADS-CoV (0.1 MOI) was adsorbed and replaced with maintenance medium. (C) Virus adsorption assay. Different concentrations of quercetin with SADS-CoV (0.1 MOI) were contacted with IPI-FX at 4 °C for 1 h and then replaced with maintenance medium. (D) Virus internalization assay. SADS-CoV (0.1 MOI) was adsorbed and then replaced with medium containing different concentrations of quercetin for 1 h and then replaced with maintenance medium. (E) Viral replication assay. SADS-CoV (after entry), replaced with maintenance medium containing different concentrations of quercetin. DMSO treatment was used as a control, and cell lysates were collected at 24 h for RT-qPCR, and SADS-CoV N content was calculated using 2^−ΔΔCT. Results are from one of three independent experiments (n = 3) and asterisks in the graphs indicate significant differences (*P < 0.05; **P < 0.01; ***P < 0.001; ns: not significant). (F) Quercetin inhibits SADS-CoV adsorption. IPI-FX was incubated with SADS-CoV (5 MOI) or different concentrations of quercetin or DMSO at 4 °C for 1 h, and virus particle adsorption was observed by IFA