S470 vesicle association with host cells is temperature-dependent. A, FITC-labeled-vesicles (2.5 μg per well) were incubated with A549 cells (5 × 104 cells per well) for 24 h at 37°C (black bars), or 4°C (gray bars). SEM is indicated, n≥2, in triplicate. B and C, A549 cells alone (left panels) or incubated with 2.5 μg FITC-labeled S470 vesicles (green, right panels) for 6 h at 37°C (B) or 4°C (C). After incubation, cells were washed, labeled with AF633-WGA (blue), fixed in 2% paraformaldehyde, and visualized by confocal microscopy.