Viral RNA Content of Bovine Leukemia Virus-infected Cells

A bovine leukemia virus (BLV)-producing cell line, fetal lamb kidney cells infected with BLV (FLK) contains one or a few copies of BLV proviral DNA in its genome. These cells contain 0.002% of viral RNA which sediments, in a sucrose gradient, at about 35S and between 18S and 28S. In cattle affected by enzootic bovine leukosis, tumor cells and circulating lymphocytes also contain one or a few copies of BLV proviral DNA integrated in their genome. However, in all cases tested (except one), no viral RNA was detected in these cells in conditions where one or two copies of viral genomic RNA per cell would have been easily detected.