NEWCASTLE-DISEASE VIRUS-INDUCED APOPTOSIS IN CHICKEN PERIPHERAL-BLOOD LYMPHOCYTES

Chicken peripheral blood lymphocytes (PBL) were infected with the GB strain of Newcastle disease virus (NDV). At 0, 1.5 and 3 h postinfection, PBL were stained with acridine orange-ethidium bromide and examined for apoptotic and necrotic indices under a UV microscope. At the end of 3 h, the cells were pelleted and were either fixed for electron microscopy or used for DNA extraction. Infected cells showed a significant amount of apoptosis and necrosis when compared with controls. Electron microscopy of the infected cells also showed characteristics of apoptosis, i.e. apoptotic bodies, margination of chromatin with crescent formation and fusion of cells. DNA extracted from virus- infected cells showed extensive fragmentation. Based on these findings it is concluded that NDV, in addition to causing necrosis in chicken lymphocytes, can induce apoptosis.