Recovery of Rauscher leukemia virus from large volumes of seeded cow's milk and from infected murine spleens.

Rauscher murine leukemia virus was used as an indicator agent to develop a methodology for the extraction and concentration of a theoretical leukemia virus from bovine milk and tissues. The indicator virus was seeded into cow's milk or was recovered from infected murine spleens. The tissue homogenates and the defatted milk were processed in a B-XVI rotor of a Spinco L-4 ultracentrifuge at a flow rate of 3 liters/hr. The efficiency of Rauscher virus recovery was greatest when the rotor was used without a gradient. A loss of between 0.6 and 0.7 log of total infectious virus, as determined by the spleen assay method, resulted when the seeded milk and murine spleens were processed. The procedures developed are presently being used in transmission experiments in an attempt to induce leukemia in the bovine.