FIG. 3.
Propagation of mutant BLV in FLK cells after transient transfection with mutant proviral DNAs. Twenty-four hours after transfection with wild-type or mutant proviral DNA, cells were replated at 2.5 × 105 cells per 10-cm-diameter dish and serially passaged every 4 days in the presence of 4 μg of Polybrene/ml. Cultured cells were serially passaged at 4-day intervals. Aliquots of passaged cells were monitored for replication of virus at the indicated times by indirect IF microscopy of fixed cell smears by using serum from a BLV-infected sheep (A), RT assay of a concentrated preparation of the virus that had been released into the growth medium (B), and monitoring formation of syncytia (C). The data represent those of a single experiment reproduced in triplicate with similar results.