Tests for RNA tumor viruses in cell substrates used in virus vaccine production

Test to detect RNA tumor viruses in cell substrates were reviewed with respect to advantages and disadvantages. Viral induction, electron microscopy, reverse transcriptase assays, density gradient centrifugation, and radioimmunoassays were performed on several cell substrates now in use or being considered for use in vaccine production. RNA tumor viruses were not detected by any of the methods except in the positive control cultures.