Equine Interferon: Absence in Equine Infectious Anemia and Kinetics of Induction in Equine Cells

Interferon was not detected in the serum of horses with equine infectious anemia (EIA). However, equine cells were capable of producing high levels of interferon both in vitro and in vivo in response to known inducers such as statolon or Newcastle disease virus. The 3 strains of ETA virus tested did not induce interferon in the fetal equine kidney cell cultures, although this system was shown to be extremely sensitive to interferon and inducers of interferon. Low levels of a viral inhibitory substance were detected in the serum of horses chronically infected with ETA about the time of the recurrent cycles of fever. This substance was not interferon because it inactivated vesicular stomatitis virus directly, and pretreatment of cells with actinomycin D did not block its activity.