Fig. 5: TMPyP4 inhibits viral infection by binding SARS-CoV-2 genomic G4s.

a Immunofluorescence of BG4 and fluorescence in situ hybridization (FISH) for viral genomic RNA (gRNA) in Vero E6 cells with or without ARS-CoV-2 infection. Scale bars, 10 μm. In the inset of selected regions, the colocalized foci of gRNA (red) with BG4 (green) are indicated by white arrows. The scale bar of inset, 2 μm. b, c The Vero E6 cells treated with 100 µM TMPyP4 were pre-transfected with the ASOs targeting viral G4s, and then the cells were infected with SARS-CoV-2 (10³ TCID50 virus/mL). At 72 h post infection, viral RNA copies in cell culture supernatants (b) were detected by qRT-PCR. Viral titers (log₁₀TCID₅₀/mL) (c) were quantified by TCID₅₀. Lower limit of detection for viral titers is indicated with a red dotted line. d–f Time-of-addition experiment of TMPyP4. The scheme shows the experimental design and the period of cell-drug incubation (d). Vero E6 cells were incubated with 100 μM TMPyP4 at the time points indicated. The cells were infected with SARS-CoV-2 (10³ TCID₅₀ virus/mL), and the cell culture supernatants viral RNA copies (e) and viral titers (f) were quantified by qRT-PCR and TCID₅₀. Data are shown as means ± SEM of three independent experiments, two-tailed Student’s t-test. ^**P < 0.01, ^***P < 0.001, ^****P < 0.0001.