FIG. 3.

Treatment of CG-4 cells with serum prevents MHV-induced cell death. Progenitor CG-4 cells were mock infected (Mock) or infected with MHV-JHM at an MOI of 10 (Virus). At 12 h p.i., cells were treated with 10% FBS in the condition medium for 10 min (Serum-treated). Serum-containing medium was then removed and replaced with the same condition medium without serum. (A) At the indicated time points p.i., a set of the cells were examined for cytopathic effect under a microscope. All photographs were taken with the digital camera (MagnaFire) attached to the microscope (Olympus IX70) with the same magnification. (B) The other sets of cells were collected and stained with trypan blue and were analyzed for cell viability. Cells that were infected with the virus but untreated with serum (Untreated) were used as a control for direct comparison. The numbers of both live and dead cells were counted in a hemocytometer under a microscope. A total of ca. 100 cells were counted for each sample. The bar in each graph denotes the mean percentage of cell death for at least three independent experiments. Error bars indicate the standard deviations of the means.