Origin and biological properties of a new feline sarcoma virus

A new strain of feline sarcoma virus (GR-FeSV) was isolated from a spontaneous sarcoma of an 8-year-old domestic house cat. The virus induced sarcomas at high incidence after a short latent period in fetal and newborn kittens and transformed cat embryo fibroblasts in vitro after 5 days. Compared to Gardner-Arnstein and the Snyder-Theilen strains of FeSV, GR-FeSV induced more pleomorphic sarcomas and larger, more rounded and discrete foci of cell transformation. GR-FeSV was shown to be defective for replication, and nonproducer transformed clones from several species were obtained at limiting GR-FeSV dilution. The defective sarcoma virus could be rescued from such transformants by superinfection with replication competent type-C viruses. The primary translational product of the GR-FeSV genome is a 70,000-dalton polyprotein that contains the amino-terminal domain of the FeLV gag gene precursor protein and a sarcoma virus-specific polypeptide. These results differentiate GR-FeSV from previously isolated FeSV strains, and establish it as an independent spontaneously occurring sarcomavirus isolate of the domestic cat.