Fig. 1

PPV infection induced ST cells apoptosis through activating caspase-9 and -3. a Morphology of PPV-infected ST cells. Morphology of PPV-infected cells was observed under fluorescence microscopy after AO/EB staining. The yellow arrow shows chromatin condensation, the white arrow shows nuclear fragmentation. b Analysis of DNA fragmentation in PPV-infected ST cells. c Analysis of ST cell apoptotic rate induced by PPV infection using flow cytometry. d The activity variations of caspases induced by PPV infection. The activities of caspase-3, -8 and -9 in PPV-infected ST cells at 1.0 MOI at 0, 6, 12, 24, 36, and 48 hpi were tested using the colorimetric assay kit. e Effect of PPV infection on PARP. The full long and cleaved PARP in PPV-infected ST cells were analyzed by western blot. f Effect of PPV infection on Fas and FasL. The presented data are the average of three independent experiments ± SD. *, p < 0.05; **, p < 0.01