Long-Term Propagation of the Rauscher Murine Leukemia Virus in Tissue Culture

Summary

An established cell line, derived from cells of the spleen and thymus of normal weanling BALB/c mice, propagated the Rauscher murine leukemia virus. The sixth passage of this culture was infected with a mouse spleen virus preparation. The infected culture has since been through 135 successive transfers, with tissue culture fluids sampled frequently. Infectivity bioassays of these fluids showed that virus collected after 194 days was as active as that taken after 21 days. Both newborn and weanling BALB/c mice responded not only to concentrated but also to unprocessed cell-free tissue culture fluids. These mice developed the typical leukemia symptoms described by Rauscher. Continued virus multiplication was evaluated by electron microscopy and assays in vivo of cell-free tissue culture fluids. The virus was identified by serum neutralization, gross pathology of infected mice, electron microscopy, and the fluorescent-antibody technique. No cytopathogenic effects of the virus have been seen in the infected cell line.