ENHANCED REPLICATION OF ORBIVIRUSES IN BOVINE TESTICLE CELLS INFECTEDWITH BOVINE VIRAL DIARRHEA VIRUS

Bovine testicle (BT) cells infected with non-cytopathogenic (NCP) bovi ne viral diarrhoea virus (BVDV) developed cytopathogenic effect (CPE) after superinfection with 7 Orbiviruses, whereas no CPE was induced by them in the absence of NCP BVDV infection. The CPE was accompanied by the enhanced replication of Orbiviruses. Seven of 10 strains of NCP B VDV induced the enhanced replication of Ibaraki virus, a member of Orb ivirus. These 7 strains of NCP BVDV were END phenomenon positive. In c ontrast, the absence of CPE and the suppression of growth of Ibaraki v irus were seen in BT cells infected with the other 3 strains which wer e END phenomenon negative. The END phenomenon negative viruses were di fferent markedly from the END phenomenon positive viruses with respect to interactions with Orbivirus. The mechanism of the enhanced replica tion of Orbivirus seems to be explained with the suppression by the EN D phenomenon positive NCP BVDV to the interferon production of Orbivir us in BT cells.