Abstract
Baby hamster kidney cells were persistently infected with lymphocytic choriomeningitis (LCM) virus (BHKpi cells). After 21 passages of the BHKpi cells infectious virus could no longer be detected; however, the cultures continued to produce LCM virus particles which interfered with the replication of infectious LCM virus in BHKpi cells and protected mice from a subsequent intracranial inoculation of infectious LCM virus. Cultures of BHKpi cells appeared to consist of three cell populations: uninfected cells, infected cells containing infectious LCM virus, and infected cells releasing interfering particles of LCM virus.