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Characterization of purely ecotropic and amphotropic naturally occurring wild mouse leukemia viruses.

Two new strains of murine leukemia virus, one (strain 4996) purely ecotropic and the other (strain 1313) purely amphotropic, were isolated from spontaneous lymphomas in aged wild mice (Mus musculus). The 4996 virus is the first wild mouse field isolate which consists solely of ecotropic virus without the concomitant presence of amphotropic virus. The 1313 isolate is distinct in host range from seven other previously described wild mouse amphotropic isolates and is also the only murine leukemia virus shown to replicate in chicken cells.