FIG. 5.

Monkey cells infected with MVA accumulate cytoplasmic viral protein with few virions, do not produce actin tails, and generate philopodia. Monolayers of BSC-40 cells were infected with WR or MVA at 0.05 PFU/cell and, 48 h later, cells were fixed and processed by a method that adequately preserves the cytoskeleton. Cytoplasmic viral p14 protein and virions were detected with anti-p14 antibody and a secondary antibody conjugated with FITC. Actin was detected with phalloidin conjugated with TRITC, and DNA was labeled with To-Pro. The upper panels showed the virus plaques produced by WR (asterisk in panel A) and by MVA. In panel C there are four WR-infected cells without connections between them, while in panel D the cells infected with MVA show a philopodium (arrow in panel D) connecting two cells. At higher magnifications (E and F), it is clear that WR strain-infected cells produced virions that exit the cells (arrow in panel E) and spread to the neighboring cells. In comparison to cells infected with strain WR, MVA-infected cells produced very few virions and a larger amount of cytoplasmic p14 viral protein, and some cells generated a long philopodium (arrow in panel F). Whereas actin tails were found in cells infected with strain WR, no such tails were observed in MVA-infected cells.