Anti-viral effect of recombinant bovine interferon gamma on bovine leukaemia virus

The antiviral activity of recombinant bovine interferon gamma (rbIFN-gamma) against bovine leukaemia virus (BLV) was evaluated by an in vitro assay. rbIFN-gamma was prepared using a baculovirus expression system and replication of BLV was measured by syncytium assay. Antiviral effects were observed when bovine and sheep cells were used as target cells or effector cells and treated with 0.1 unit/ml of rbIFN-gamma. Formed syncytium numbers were reduced less than 1/20 when these cells were treated with 10 units/ml of rbIFN-gamma. However, the antiviral effects on cells of heterologous species were decreased and more than 1000 units/ml of rbIFN-gamma were required to induce an anti-BLV effect on the combination of CC81 cells as target cells and Bat2Cl6 cells as effector cells, which originated from the cat and bat, respectively. When the degree of BLV production was estimated by reverse transcriptase (RT) activity, no antiviral effect of rbIFN-gamma was induced soon after the treatment, but it was evident in the cells persistently infected with BLV. These results showed that rbIFN-gamma suppresses the replication of BLV in vitro, but has effective biological activity on cells of homologous species.