Fig. 6.

Inhibition of HCoV-NL63 infectivity in human airway epithelial cells by caffeic acid. Calu-3 cells were infected with HCoV-NL63 at a MOI of 0.05 and immediately treated with caffeic acid for 36 h at 32 °C. Images of virus-induced CPE effect were photographed by a light microscope (A, top). In addition, mock, infected, and infected/treated cells were performed using immunofluorescence staining anti-HCoV-NL63 immunized sera and secondary antibody Alexa Fluor anti-mouse IgG (A, middle); total cells were stained with DAPI (A, bottom). Infectivity was determined according to the ratio of HCoV-NL63-positive cells to total cells (B). **, p value < 0.01; ***, p value < 0.001 compared with un-treated infected cells.