Sensitive in vivo assay for detection of murine leukemia viruses

A test is reported for the in vivo detection of the replicative ability of murine leukemia viruses (MLV) in the BALB/c mouse strain. Growth in the spleen was assayed by the complement-fixation assay for MLV group-specific antigen after injection of newborn mice. Low doses of laboratory-derived and wild-type MLV from cell-culture and animal-grown sources were detected as early as 7 to 14 days postinoculation. The sensitivity of this in vivo test compared favorably with in vitro assays for MLV. In vivo detection of MLV replication was correlated with long-term oncogenicity.