FIG 8.

Boceprevir was capable of completely suppressing SARS-CoV-2 in Vero E6 cells. Vero E6 cells seeded the previous day in T25 flasks were infected with SARS-CoV-2 at an MOI of 0.00002 followed by treatment with 1-, 1.5-, 2-, 2.5-, 3-, and 5-fold EC₅₀ boceprevir, which was administered immediately after infection and subsequently at the indicated time points when cells were split, as described in Materials and Methods. (Left) Percentages of SARS-CoV-2-infected cells on the specified days postinfection were determined by anti-spike protein immunostaining of replicate cultures derived following cell splitting and treatment. (Middle) SARS-CoV-2 RNA titers determined in cell culture supernatants as genome copies per milliliter on the specified days postinfection were determined by RT-qPCR assays. The black line indicates the LLOQ. In the left and middle panels, to facilitate comparisons, bars are color coded according to the day postinfection, and blue and red dotted lines were inserted to highlight day 1 and 3 values of the nontreated culture, respectively. (Right) Replicate cultures were derived following cell splitting and treatment, immunostained for the SARS-CoV-2 spike protein (green) and counterstained with Hoechst dye (blue), and images were acquired, as described in Materials and Methods. Cultures summarized in this figure are derived from different experimental setups, each including an infected nontreated control culture, which showed viral spread comparable to that in the depicted representative culture. *, culture was terminated, or infection data not recorded, due to virus-induced cell death; ^#, culture was maintained for a total of 17 days without indication of infection (no observation of single SARS-CoV-2 spike protein-positive cells and RNA titers were around the LLOQ).