The influence of host adaptation of Rous sarcoma virus on the transfecting activity of its DNA provirus.

Mammalian cells transformed with either Prague strain Rous sarcoma virus of subgroup C (XC cells) or Schmidt-Ruppin strain Rous sarcoma virus of subgroup D (RSCH cells) yielded virus upon fusion with chick cells. Virus was also rescued by transfection of DNA from these cells on to chick cells. However, virus rescue did not occur upon transfection of duck cells, and fusion with duck cells led to virus rescue only from RSCH and not from XC cells. To investigate this restriction on the duck cells the non-defective Prague strain of Rous sarcoma virus of subgroup C (PR-RSV-C) was adapted for efficient replication in duck embryo cells (daPR-RSV-C) by long-term passage in vitro. However, a second PR-RSV-C isolate, rescued from the rat XC sarcoma line (XC DNA 940 virus), failed to adapt to growth in duck cells. When transformed with daPR-RSV-C, which replicates in duck cells as well as in brown leghorn embryo (BLEF) cells, duck cells yielded DNA which transfects fresh duck cells, in contrast to DNA isolated from chicken or duck cells transformed with parental PR-RSV-C.