Evidence for the Defectiveness of the Harris Strain of Rous Sarcoma Virus

Summary

A noncytopathic avian leukosis virus was isolated from the Harris strain of Rous sarcoma virus (HA-RSV) and was referred to as Rous-associated virus (RAV-6). From viral interference and neutralization tests, RAV-6 was found antigenically identical to HA-RSV. HA-RSV was classified previously as a subgroup B virus based on its host range. Four clones of transformed cells, whose supernatant fluid produced no neoplastic changes on chick embryo fibroblasts (CEF) susceptible to all known avian leukosis-sarcoma viruses (C/O), were derived from HA-RSV-infected C/O CEF by use of duck embryo fibroblasts as feeder layers. One of these clones was activated by all 8 strains of avian leukosis viruses tested, and the “activation potential” of the clone approached that of L-R cells derived from the Bryan high-titer strain of Rous sarcoma virus (BH-RSV). The other 3 clones had very low to no activating potential.