PARAINFLUENZA (SENDAI) VIRUS INFECTS CILIATED CELLS AND SECRETORY-CELLS BUT NOT BASAL CELLS OF RAT TRACHEAL EPITHELIUM

Sendai virus is a common respiratory pathogen in rodents. In the airways of rats infected with Sendai virus, viral antigen is present in epithelial cells, but whether all types of epithelial cells are infected is unknown. Because each type of epithelial cell has specific functions that could be affected by viral infection, we asked whether ciliated cells, secretory cells, and basal cells of the rat tracheal epithelium become infected by Sendai virus. We inoculated pathogen-free rats intranasally with Sendai virus, killed the rats 1 to 12 days after inoculation, and prepared the tracheas for double-labeling immunohistochemistry and for electron microscopy. In other studies, we maximized the infection by inoculating rats with a 100-fold higher titer of the virus, by inoculating weanling rats, or by inoculating tracheal explants with Sendai virus in vitro. We also determined whether Sendai virus can infect basal cells of tracheal explants after removal of the overlying columnar epithelial cells. Immunohistochemical studies showed that at the peak of the infection (5 days after inoculation), 30% of the surface epithelial cells stained for Sendai virus antigen, but no basal cells were stained. Electron microscopic examination confirmed the presence of viral particles in ciliated cells and secretory cells, but none were found in basal cells. No basal cells were infected under the conditions that maximized the infection. We conclude that ciliated cells and secretory cells of the rat tracheal epithelium become infected by Sendai virus, but basal cells do not become infected.