Figure 6.

Cellular uptake of spikeS1 into SDC transfectants. WT K562 cells and SDC transfectants were incubated with spikeS1 for 18 h at 37 °C. After incubation, the cells were washed, trypsinized, fixed, permeabilized and treated with FITC-labeled antibodies specific for the N-terminal His-tag of the recombinant spikeS1. Cellular uptake of spikeS1 was then analyzed with imaging flow cytometry and confocal microscopy. (A) A representative flow cytometry histogram showing the intracellular fluorescence of spikeS1-treated WT K562 cells and SDC transfectants. (B) Detected fluorescence intensities were normalized to spikeS1-treated WT K562 cells as standards. The bars represent the mean ± SEM of three independent experiments. Statistical significance vs. standards was assessed with ANOVA. ** p < 0.01. (C) BF and fluorescent cellular images of spikeS1-treated WT K562 cells and SDC transfectants. Scale bar = 20 μm. (D) Imaging flow cytometry visualization of colocalization between SDCs and spikeS1. Representative images of four independent experiments are shown. Scale bar = 20 μm. The indicated BDS of spikeS1 and SDCs represent the mean ± SEM of four independent experiments. Statistical significance between the groups was assessed with ANOVA. No statistically significant differences were detected. (E) Colocalization of spikeS1 and SDC4 detected with confocal microscopy. Representative images of three independent experiments are shown. Scale bar = 10 μm. MOC ± SEM and PCC ± SEM for the overlap and colocalization of SDC4 with spikeS1 (indicated on the image) was calculated by analyzing 12 images with an average of 12 cells in each image (from 3 separate samples).