Fig 7.

OM-5 inhibits epithelial cell infection by SARS-CoV-2. A, Vero cells were pretreated with PBS or OM-85 (0.24-1.92 mg/mL) for a total of 72 hours and then infected with SARS-CoV-2 (isolate USA-WA1/2020, 15 pfu/well) for 2 hours. Plaques were counted as described in Methods. B, Calu-3 cells treated with PBS or OM-85 (0.24-1.92 mg/mL) for 72 hours were infected with SARS-CoV-2 (WA/2020, ∼100 pfu) for 2 hours. Cells were then cultured for 48 hours in medium containing the original OM-85 concentrations. Viral titers were determined by dispensing 10-fold serial dilutions of Calu-3 culture supernatants on 96-well indicator Vero plates. Plaques were counted as described in Methods. The number of pfu/well of Calu-3 plates was calculated by dividing the number of plaques on indicator Vero plates by the dilution factor. Shown are average numbers ± SEM of pfu detected in 4 (C) or 8 (D) SARS-CoV-2–infected replicate wells pretreated with PBS or increasing OM-85 concentrations. Data were pooled from 2 independent experiments (Fig 7, A and C) and 1 representative experiment (Fig 7, B and D). A 2-tailed t test was used for statistical analysis after assessing the normality of sample distribution.