Pathogenesis of bovine parainfluenza 3 virus infection in organ cultures

Ultrastructural features of experimental parainfluenza type 3 virus pneumonia in calves

Ultrastructural changes observed in the acute and repair stages of experimental P13 virus pneumonia in young calves are described. In the early acute stage of the pneumonia, paramyxovirus replication was observed within epithelial cells of the respiratory tract and within alveolar macrophages. There was loss of cilia and of ciliated cells in small bronchi and bronchioli. Proliferation of non-ciliated bronchiolar cells (Clara cells) produced zones of hyperplastic bronchiolar epithelium and, within alveoli, widespread proliferation of Type 2 pneumomonocytes led to alveolar epithelialization. Necrosis was noted in both bronchiolar and alveolar epithelium. Early evidence of repair was the appearance of macrophages on the surface of damaged bronchiolar and alveolar epithelium. Organization of bronchiolar exudate involving fibroblasts and macrophages was widespread in calves killed between 7 and 12 days after infection and, in calves killed at 12 days and subsequently, bronchiolitis obliterans was widespread. Re-epithelialization of damaged bronchiolar mucosa and alveoli also occurred.

Pathogenesis of human parainfluenza type 3 virus infection in hamster tracheal organ culture

Hamster tracheal organ culture was employed as a model for the study of the pathogenesis of human parainfluenza type 3 virus infection. It clearly supported replication of the virus over a 2-week period of time. Infected tracheal explants were examined with light, electron, and immunofluorescence microscopy. They exhibited specific cytopathologic alterations including nuclear swelling and chromatin margination, multinucleated syncytia and binucleated epithelial cells, and fibroblasts and chondrocytes. Focal destruction and denudation of the respiratory epithelium occurred in later stages of infection. Virus was detected in close association with cilia and was observed budding off the unit membrane of epithelial cells.