Replication of parainfluenza type-3 virus and bovine respiratory syncytial virus in isolated bovine type-II alveolar epithelial cells.

The objectives of our research were to determine whether bovine pulmonary type-II alveolar epithelial cells could be isolated from bovine lung and maintained in tissue culture and to determine whether isolated bovine type-II alveolar epithelial cells would support productive viral replication of bovine parainfluenza type-3 virus and bovine respiratory syncytial virus. Type-II alveolar epithelial cells were isolated from lungs of 4- to 7-day-old male Holstein calves by enzymatic dissociation of pulmonary tissue with trypsin and by separation of cells with the use of filtration and centrifugation on continuous Percoll gradients. Cells were further separated by panning on IgG-coated plastic plates and by lectin binding. Isolated type-II alveolar cells were maintained on basement membrane-coated tissue cultured plates. In culture, type-II cells formed alveolar structures and maintained other cytologic features of type-II cells, including osmiophilic lamellar inclusions. Cell cultures were inoculated with and supported productive replication of bovine parainfluenza type-3 virus and bovine respiratory syncytial virus. This was determined by recovery of infectious viruses from inoculated cell cultures and by identification of viral structures in type-II alveolar epithelial cells by transmission electron microscopy.