Infection of an established mouse cell line with cell-free Rauscher leukemia virus. I. Cytological study with the electron microscope.

Infecting mouse bone marrow cells (JLS-V9) with cell-free Rauscher leukemia virus demonstrated that monolayers of JLS-V9 cells were susceptible to infection with both cell-free plasma and tissue-culture-propagated Rauscher virus. The infected cultures maintained the continuous release of the virus. Cells and concentrated supernatant fluids from infected cells were periodically examined under the electron microscope by thin sectioning and negative staining techniques after inoculation with either mouse plasma or tissue-culture-propagated virus. After adsorption the virus underwent a prolonged eclipse or latent period. Virus budding was initially detected about 10 days after primary infection. These observations were further confirmed by the simultaneous appearance of extracellular virus. The budding process was followed by accelerated virus multiplication which reached maximum production 2-3 weeks later. Before the onset of budding no significant morphologic changes were seen in the infected cells.