Apoptosis in chicken embryo fibroblasts caused by Newcastle disease virus

The GB strain of Newcastle disease virus (NDV) was used to infect chicken embryo fibroblasts (CEF). At various times after infection, CEF were harvested and processed for DNA extraction, flow cytometry and electron microscopy. Agarose gel electrophoresis of the DNA at 12 h after infection, showed a laddering pattern, indicating fragmentation of cellular DNA. Flow cytometry analysis of the infected cells showed an increase in the population of smaller cells (apoptotic cells). Electron microscopic examination showed extensive cellular necrosis, but also showed some other cells with condensed chromatin and with extensive perinuclear fragmentation of chromatin; apoptotic bodies could also be readily seen. These data suggest that NDV infection of CEF causes apoptosis, in addition to necrosis.