Tumors induced in hamsters by simian virus 40: persistent subviral infection

The cells of two hamster ependymomas, originally induced by intracerebral inoculation with simian virus 40 in newborn animals, have been serially cultured in vitro. None of the virus was detected in cell-free culture fluids or cell lysates. All cells retained their neoplastic potential when newborn hamsters were inoculated. Data suggest that viral nucleic acid is permanently present in some tumor cells.