Genetic stability of rDNA production systems, a case report

Producing rDNA proteins to be used as human therapeutic agents requires a biological production system during both storage and growth. The genetic make-up of a biological system is usually known through the laboratory history of the host strain and the process of vector construction. All master cell banks prepared for the production of medicinal products are fully characterized at the genetic and biochemical level. Whether these characteristics can be consistently maintained, particularly when the cells are propagated through a high number of generations and the culture grown into tens of thousands of litres, will have significant effects on the quality of the final products. Considerable experience and data regarding the stability of biological production systems involving plasmid and E. coli or yeast have been accumulated during the past 10 years. These data, including size and restriction analyses of the plasmid and sequence determination of relevant portions of the plasmid DNA isolated from cells collected before culture harvest, demonstrated that plasmid alteration at the structural level do occur, and some with high frequency or concentration. Assisted by such genetic information, criteria for accepting or rejecting a fermentation run can be established.