Subcellular localization of VII⁻virus particles analyzed by transmission electron microscopy.

A549 cells were infected with VII⁺ or VII⁻virus particles at 37^°C for 60 min, washed in warm virus-free medium, further incubated at 37^°C for 5 or 240 min, fixed in glutaraldehyde, and processed for Epon embedding and thin section EM analysis. (A) Representative images of virions in the cytosol or the nuclear membrane (arrows), and in vesicles (arrowheads). (B) Quantification of virions at the plasma membrane (blue bars), in vesicles (red), the cytosol (green), and on the nuclear membrane (violet). The Top panel represents the raw data, including the number of virions (v) and cells (c) for each condition. The Bottom panel shows the normalized data as a fraction of the total number of virions for each condition. Note the enrichment of VII-less virions in multi-vesicular structures, and the strong reduction in wild-type virions 300 min post-infection, indicative of capsid disassembly [49, 88, 89]. The black bar in (A) represents 0.1μm.