Leukemogenic activity of ether-extracted Rauscher leukemia virus.

After rapid multiple extractions of mouse plasma virus with ether, the aqueous solution contained viral nucleoids that were infectious when inoculated intracranially into newborn BALB/c mice. The infectivity associated with the ether extract was not neutralized by the specific antibody prepared against the whole virus. No intact virus has been seen in these preparations. Treatment with ether completely removed the virus envelope from the particle and produced an apparently homogeneous preparation of viral nucleoids. After the extractions with ether, leukemogenic activity was inactivated by exposure to ribonuclease. The leukemogenic activity of the many-passaged Rauscher virus that has been propagated in tissue culture and that has low infectivity was also retained, and, in two experiments in which material was inoculated intracranially into mice, this activity appeared to have been enhanced by multiple extractions with ether.