Figure 1. NDV infection induces both intrinsic and extrinsic apoptosis in HeLa cells.

(A) Cytopathic effects of NDV infection. HeLa cells were infected with 1 MOI of NDV. Images were taken under microscope at 4, 8, 12, 16, 20, 24 h.p.i.. (B) Growth curve of NDV in HeLa cells. The culture medium in Figure 1A was collected at 0, 4, 8, 12, 16, 20, and 24 h.p.i., and subjected to TCID₅₀ assay using DF-1 cells. Virus growth curve was plotted based on three biological replicates, and error bars represent standard deviation of the mean (n=3). (C) Activation of intrinsic and extrinsic apoptosis by NDV infection. HeLa cells were mock-infected or NDV-infected, and harvested at 0, 4, 8, 12, 16, 20, and 24 h.p.i.. The NDV-induced apoptosis was analyzed with Western blot using anti-caspase 8, anti-caspase 9, anti-caspase 3, anti-PARP. NP was detected to monitor virus replication and β-actin was detected as loading control. The intensities of bands were determined by densitometry, normalized to β-actin, and shown as fold change (virus:mock).