Figure 3.

ATRA inhibits SARS-CoV-2 replication (A) Assessing the antiviral effect of ATRA in VeroE6/TMPRSS2 cells. VeroE6/TMPRSS2 cells treated with ATRA (0.1–100 µM) for 3 h prior to infection were infected with SARS-CoV-2 (MOI = 0.05) and washed off the unbound virus at 2 h of infection. Cell viability assay and RT-PCR were performed on the attached cells and supernatant culture medium respectively, 48 h after infection. (B) The results of the cell viability assay. IC₅₀ was calculated for the inhibition of SARS-CoV-2 induced cell death. Error bars obtained from triplicate testing. p-value < 0.005 (***) (C) Viral quantification by RT-PCR. Error bars obtained from duplicate testing. p-value < 0.005 (***) (D) Immunostaining of SARS-CoV-2 N protein in infected cells. VeroE6/TMPRSS2 cells treated with ATRA (1, 10, 25 µM) 3 h before infection were infected with SARS-CoV-2 (MOI = 0.05). After 24 h of infection, cells were fixed with 4% paraformaldehyde and immunostained. Red stained cells represent SARS-CoV-2 N protein, blue-stained nuclei with DAPI. (E) Schematic representation of the time of addition assay of ATRA. (F-H) The results of RT-PCR for ATRA (F), Remdesivir (G) and Camostat (H). The result of full-time colored grey, entry colored blue, and post-entry colored red. Error bars obtained from duplicate testing. p-value < 0.005 (***).