Rescue of Defective Murine Sarcoma Virus Genome From 50 Clones of a Nonproducer Hamster Tumour Cell Line

A cell line (HT-1) derived from a hamster tumour induced by the Moloney sarcoma virus has been extensively used for preparation of murine pseudotype sarcoma viruses (Huebner et al. 1966; Hartley et al. 1969). Infectious virus could not be isolated from these cells nor was the group specific (gs) antigen of the murine C-type RNA viruses detectable in complement-fixation tests (Huebner et al. 1966). In further studies with this cell line, clonal sublines were derived and tested for infectious virus and virus particle production, gs antigen using both complement-fixation and precipitation-ingel assays, and the presence of virus genome by a highly reproducible rescue technique. HT-1 cells in the 80th in vitro passage were seeded into ten 60 × 15 mm. plastic Petri dishes (50 cells/dish). Each culture yielded 5 to 10 individual colonies, of which five were isolated by trypsinization within glass cloning rings. Each of the 50 clones was maintained separately in Eagle's basal medium with 10% foetal bovine serum.