Fig. 4. Synergistic antiviral potential of disulfiram/ebselen and hydroxychloroquine (HCQ). (a) The antiviral activities of disulfiram and ebselen against SARS-CoV-2 were determined on Vero E6 cells using immunofluorescence assay to detect SARS-CoV-2 N protein expression (green). (b) Viral infection was quantified by a high-content image analysis system and the average infection rate of no drug treatment was set as 100% for calculation of the 50% inhibitory concentration (IC₅₀). For the 50% cytotoxic concentration (CC₅₀), Vero E6 cells treated with the indicated compound were assayed by Cell Counting Kit-8. IC₅₀ and CC₅₀ were calculated by Prism software. (c) The SARS-CoV-2 infection rates in Vero E6 cells treated with hydroxychloroquine (HCQ) plus disulfiram or ebselen were determined as described above, and shown as means and standard deviations (n = 3). The average infection rate of six sets of experiments with no drug treatment was set as 100%. The p values were calculated by student's t test.