Changing issues of quality control: diploid and non-diploid cell lines.

Early viral vaccines were prepared from primary monkey kidney cell cultures. However, primary cell cultures can be highly variable and also present a risk of contamination by endogenous viruses. The development of human diploid cell lines for vaccine production provide greater assurance of consistency and freedom from contaminating viruses. Continuous cell lines present considerable advantages in the preparation of proteins for therapeutic use. The perceived risks associated with the use of these cell lines include those of retroviral contamination, oncogenic DNA and consistency of final product during the extended life in culture. Advances in molecular biologic and analytical chemistry procedures have enabled extensive characterisation not only of the cells, but also of the product itself. The degree of testing which can now be performed on the product, to ensure its safety and consistency, should lead to a reappraisal of testing regimes applied to the cells themselves.