Fig. 7: Reduction of cellular heparan sulfate by NSC80997 treatment inhibits binding and entry of SARS-CoV-2.

a Cell surface binding of recombinant SARS-CoV-2 spike protein to Vero-E6 (left) and A549 (right) cells treated with increasing concentrations of NSC80997 or DMSO control for 24 h or after heparinase treatment (HSase). Binding was assessed by flow cytometry and is presented as mean fluorescence intensity (MFI) ± SEM (arbitrary units) from 3 independent experiments. ***P < 0.0001 (ANOVA). b Infection of NSC80997 or control-treated Vero-E6 cells with SARS-CoV-2 S protein pseudotyped virus expressing luciferase. Infection was measured by the addition of Bright-Glo and detection of luminescence. Data is presented as mean relative light units (RLU) ± SEM from 3 independent experiments. ***P < 0.0001 (ANOVA). c Relative infection of SARS-CoV-2 (strain USA-WA1/2020) (left) and percent viable cells (right) in Vero-TMPRSS2, Caco-2, and Huh7.5 cells treated with increasing concentrations of NSC80997 or DMSO control. Infection was monitored by immunofluorescence using antibodies against SARS-CoV-2 nucleocapsid protein after 24 h pre-treatment with NSC80997 and 18 h exposure to virus with continued NSC80997 treatment. Cell viability was measured by Sytox Green nuclear stain. The experiments were performed in duplicate twice. The average values from each experiment were used to calculate the IC50 values and are shown as relative infection and cell counts compared to control, respectively. Non-linear fit curve is shown.