The isolation of bovine ephemeral fever virus in cell cultures and evidence for autointerference

Bovine ephemeral fever (BEF) virus was isolated from infected fresh cattle blood directly into Vero cell cultures. One cycle of rapid freeze-thaw destroyed the infectivity of the virus to Vero cells. The infectivity to baby mice by intracerebral inoculation, on the other hand, was only reduced. The occurrence of autointerference due to the presence of defective interfering particles in cell culture was also noted. BEF virus strain 919 was propagated to some extent in bovine kidney, testis and synovial cell monolayers, producing cytopathic effect (CPE) in 24 h. However, the CPE was nonprogressive and the addition of antinomycin D to the medium improved the virus titre only slightly.