Newcastle disease virus-induced apoptosis in the peripheral blood mononuclear cells of chickens.

Specific pathogen-free chickens were inoculated with the GB strain of Newcastle disease virus by the ocular route, and were killed at daily intervals after infection. Peripheral blood mononuclear cells (PBMCs) were harvested for DNA extraction, electron microscopy, and flow cytometry studies to detect the presence of cellular apoptosis and necrosis. Extracted DNA showed fragmentation at 4 and 6 days after infection. Electron microscopy showed that the chromatin of the lymphocytes became condensed and occasionally crescent-shaped; apoptotic bodies could also be seen. Some heterophils became darkly stained and their nuclei degenerated; others seemed to have lost their cytoplasmic membrane, but had intact granules and condensed chromatin. Flow cytometry studies showed that the number of normal PBMCs gradually decreased from 99.04% at the beginning of the infection to 45.24% on the sixth day of infection, with a concomitant increase of apoptotic cells. The results show that PBMCs of chickens exhibit typical signs of apoptosis after infection by the Newcastle disease virus.