Detection and elimination of endogenous retroviruses and retrovirus-like particles in continuous cell lines

Conventional safety tests are sufficient for inspecting biological products provided no retrovirus-like particle is present in substrate cells. But if so, changing the cell line to another would be the best course of action but of course unwise for cell lines derived from rodents due to the difficulty in obtaining a particle-free cell line. Otherwise, biological and/or physical means for eliminating such particles would be best. A general procedure should be available for inactivating retroviruses in vaccines. A standard method for selectively inactivating the biological activity of nucleic acid but not protein by physical (e.g., UV or radiation), chemical, or biological (e.g., nuclease treatment following particle disruption) treatment should be developed since it is known that the essential biological activity of the particles is on the RNA genome. If a product is too unstable to permit application of these methods, elimination of the particles can be carried out by physical means since they are sufficiently large.