Spontaneous leukemia viruses: lymphomagenic ecotropic viruses of AKR mice

The spontaneous leukemia (SL) viruses are ecotropic lymphomagenic viruses isolated from AKR spontaneous lymphomas. These viruses are produced stably by continuous cell lines from spontaneous lymphomas and by a cell line derived from the bone marrow stroma of an AKR mouse neonatally inoculated with an SL virus. All cell lines cloned from the parent lymphoma cell lines consistently produce SL viruses. These viruses can be passaged in vivo and maintain their leukemogenic properties. Cloned isolates of SL viruses accelerate lymphoma in AKR mice and induce thymic lymphoma in mice of other strains. Thus their lymphomagenic properties are conclusively shown. In a study with the use of a sensitive host range assay, xenotropic and/or dual-host range viruses are consistently found in spontaneous lymphoma and cell lines derived from them. However, viruses able to replicate in mink lung cells are not expressed in SL virus-induced lymphomas or their derived cell lines.