Regulatory philosophy and acceptability of cells for the production of biologicals.

The issue of what types of cells should be considered acceptable for use in manufacture of biologicals dates back to the early 1950s. One of the central points in the discussions and debates over the past 35 years has been the possibility that the use of a given type of cell would result in unsafe products. Of the possible sources of risk, the presence of endogenous viruses in cell substrates has been the only one with realistic and practical implications for public health. The discovery of SV-40 in polio vaccines derived from primary Rhesus kidney cells made the issue of viral contaminants a very real one. Avian leukosis viruses have also been identified as endogenous agents that were carried over into products derived from chicken eggs. It is now important for regulatory policy to continue to be flexible, and to be guided by our technological capabilities in addressing safety issues associated with endogenous viral contaminants.