An A Particle, Probably of Bovine Origin, Detected in BHK21 Cells Infected with Bovine Syncytial Virus

To initiate an investigation of bovine syncytial virus, two cultures of bovine embryonic spleen cells were obtained from Dr M. J. van der Maaten. One of these cultures was already inoculated with bovine syncytial virus. To propagate the virus, inoculated and uninoculated cultures of bovine embryonic spleen cells were mixed. The cells were initially grown in Eagle's medium with 20% foetal calf serum, but this was changed after a few passages to Eagle's medium plus 10% tryptose phosphate broth and 10% foetal calf serum (ETC). After several passages the spleen cells ceased to grow well, so an attempt was made to propagate the virus in BHK 21 cells. Infected spleen-cell cultures were mixed in ETC medium with BHK 21 cells and syncytia developed in the mixed cultures. The cells were subcultured at 2- or 3-day intervals, and after 3 weeks the cytopathic effect was widespread.