Murine sarcoma virus (Harvey): characteristics of focus formation in mouse embryo cell cultures, and virus production by hamster tumor cells.

Abstract

AbstractTitrations of the Harvey isolate of murine sarcoma virus (MSV) in mouse embryo cells indicated that infection of a cell with MSV alone might not be sufficient to induce focus formation. Addition of high concentrations of Moloney leukemia virus to diluted MSV preparations resulted in an increased number of foci, consistent with the hypothesis that Moloney leukemia virus can act as a helper for defective MSV (Harvey).A transplantable hamster tumor line was established by inoculation of fragments from an MSV‐induced mouse tumor into newborn hamsters, followed by repeated passage in adult hamsters. Tumor tissue from the 25th hamster transplant generation of this tumor line was used to establish a cell line — “B‐34” — in culture. B‐34 cells elaborated a filtrable agent which produced sarcomas and other lesions characteristic of MSV when inoculated into newborn hamsters, but which did not produce any observable pathological changes when inoculated into newborn mice. However, mixed cultures of B‐34 cells and normal mouse embryo cells, when superinfected with Moloney leukemia virus, released MSV infective for both mice and mouse embryo cell cultures.