Persistent infection of BHK-21 cells with pneumonia virus of mice.

Trypsinization of BHK-21 cells 72 h after primary infection with pneumonia virus of mice yielded clones of persistently infected cells which specifically adsorbed murine erythrocytes. We describe one clone of cells, the progeny of which, after more than 100 passages, still bore viral antigen demonstrable by immunofluorescence and immune electron microscopy, but produced little or no detectable infectious virus.