Pathogenesis of infectious bovine rhinotracheitis (IBR) virus infection in bovine fetal tracheal organ cultures

Abstract

Bovine fetal tracheal organ cultures were infected with a field strain of IBR virus and the effect of the virus was assessed by observing ciliary activity and cytopathic changes in unstained, hematoxylin-eosin-stained, and fluorescent-labeled antibody preparations of the culture system. The virus was quantitated in bovine fetal kidney cell cultures. The IBR virus was first detected in infected organ cultures at 8–12 h postinoculation and persisted for at least 23 days. A decrease in ciliary activity was not observed until 48 h postinoculation, at the same time that the first signs of cytopathic effect was seen in the unstained cultures. The viral infection first appeared as discrete foci of rounded cells on the epithelial surface, but then spread from cell to cell beneath the ciliated epithelial cells leading to early degeneration of the non-ciliated epithelial cells and microvesiculation which eventually resulted in a massive sloughing of the whole epithelial layer. The virus was not limited to the epithelial layer but infected a variety of cell types among the submucosal and connective tissue components of the organ cultures.