Time course of Newcastle disease virus-induced apoptotic pathways

Newcastle disease virus (NDV) causes economically significant Newcastle disease (ND) in almost all birds worldwide. Previous studies have shown that NDV induces caspase dependent apoptotic pathways in infected cells. In the present study, time course induction of apoptotic pathways in Vero cells is described. In NDV-infected cells, caspase-8 activity, percentage of cells showing TRAIL expression was higher at 24 h p.i. (post-infection) compared to 48 h p.i. In contrast, caspase-9 activity, efflux of cytochrome c, loss of mitochondrial membrane potential was higher at 48 h compared to 24 h p.i. The caspase-3 activity was high both times. Based on these results, it was concluded that at 24 h p.i., NDV induces apoptosis through extrinsic apoptotic pathway while at 48 h p.i. predominantly through intrinsic apoptotic pathway.