ABSTRACT
For many years, animals and primary cell cultures from animal tissues have been used for research and for the manufacture and testing of vaccines. In the 1960s, human diploid fibroblast cell lines were developed for the manufacture of vaccines, and more recently, continuous cell lines from other species have been used in biotechnology. Notable examples include BHK cells for foot-andmouth disease vaccine, CHO cells for production of recombinant proteins, and hybridoma cell lines for the production of monoclonal antibodies (Griffiths and Doyle, 1999; Stacey, 2000). The increased use of cell lines for the manufacture of a range of biological medicines has been driven by the need for more reproducible and safe cell substrates. In the 1950s, batches of polio vaccine were found to be contaminated with SV40 virus originating from the primary monkey kidney cells used in the manufacturing process. Although studies of vaccinees failed to show any direct adverse
effects at the time, this incident in particular highlighted the need for safe and standardized cell substrates. Cell lines appeared to offer a solution but were susceptible to genetic variation and contamination if maintained by serial passage. Fortunately, mammalian cell lines are generally amenable to cryopreservation, and this made it possible to prepare reliable cell banks of homogenous aliquots that could be stored in a stable state at ultra-low temperature. Sample ampoules from the banks could then be thoroughly investigated for infectious agents before use, thus, enhancing the safety of vaccines produced from the banked cells. The benefits of standardized cell banks can be applied to all applications of cell lines, and cell-banking procedures are a vital preliminary step for any application of cell lines in which reproducibility and reliability are key issues.
