Fig 5.

OM-85 reduces S1 protein–mediated attachment to epithelial cells. Representative flow cytometry plots showing SARS-CoV-2 S1 protein binding to parental HEK293T cells and HEK293T cells stably transfected with human ACE2 (ACE2/HEK293T) (A) and Vero E6 and Calu-3 (B) epithelial cells. Cells were treated with PBS or OM-85 (1.92 mg/mL) for 72 hours and then incubated with or without recombinant His-tagged S1 protein, followed by an anti–His-PE antibody. S1 binding was assessed by flow cytometry. C, Effects of OM-85 on S1 protein binding to Vero E6 or Calu-3 cells. Data are shown as percentages of S1 protein–binding cells in OM-85–treated vs PBS-treated cultures (n = 5-6 wells/group from 3 [Vero E6 cells] or 2 [Calu-3 cells] independent experiments). An unpaired, 2-tailed t test was used for statistical analysis after testing for normality of sample distribution. FSC, Forward scatter; PE, phycoerythrin.