Alteration of chicken heterophil and macrophage functions by the infectious bursal disease virus

The effects of the infectious bursal disease virus (IBDV) on chicken heterophils and macrophages are reported. Short-term incubation of IBDV with heterophils causes an activation of cellular oxidative burst, a decrease in phagocytosis and cellular migration, and an increase in cellular adherence to the IBDV-infected chicken embryo fibroblasts. Under electron microscopic examination, heterophils show condensed chromatin and packets of intact granules, either free or being phagocytized by macrophages, indicating that the heterophils are undergoing apoptosis. The HD-11 cells, a virus-transformed macrophage cell, after 1-2 h of infection by IBDV in vitro, become less responsive of chemoattractant and less capable of performing phagocytosis. After a longer period of infection, IBDV is able to multiply in the HD-11 cells, and starts to cause cells to undergo apoptosis. This IBDV-induced alteration in heterophil and macrophage functions and the death of these phagocytic cells may play a role in the subsequent immunosuppression in the affected chickens.