Bovine leukemia virus inhibiting activity in fetal calf serum

We have obtained a new cell line persistently infected with bovine leukemia virus (BLV). BLV-infected cells can be easily detected by indirect immunofluorescence or immunoperoxidase staining technique. The morphology and number of infected cells seem to be related to serum concentration in culture medium: fetal calf serum (FCS) showed a marked effect on virus growth and virus distribution in cell cultures. All of the commercial lots of FCS tested showed BLV inhibiting activity very similar to that previously described for other viruses.