Fig 5.

Ultrastructural analysis of capsid and virion formation in K.VP1-2ΔNLS-infected cells. RSC were infected in parallel with KOS or the mutant virus K.VP1-2ΔNLS at an MOI of 5, fixed at 16 h postinfection, and processed for thin-section electron microscopy as described in Materials and Methods. (a to c) K.VP1-2ΔNLS; (d to f) KOS. Capsid formation was readily apparent for both the mutant and wt viruses (a and d; small white arrows indicate nucleocapsids, and the large white arrowhead indicates a particle in primary envelopment). Cytoplasmic envelopment was also observed for the mutant and wt viruses (b and e; black arrows indicate wrapping during secondary envelopment). Finally, panels c and f show the presence of assembled virions for the mutant and the revertant, respectively. (g and h) Further examples of assembled extracellular virions, which were readily observed for the mutant virus. In general, little difference in the main ultrastructural features of infection were observed for the wt versus the mutant strain, and all qualitative features of capsid and virion assembly could be observed. Similar results were obtained with the K.VP1-2ΔNLS revertant virus and with different cell lines (Vero and HaCaT cells). Bars, 500 nm.