Downstream Processing of Proteins from Mammalian Cells
This chapter focuses on the downstream processing of therapeutic proteins produced in mammalian cells. Mammalian cells provide special opportunities for controlling product composition and quality, particularly with regard to glycosylation and subunit assembly. Special considerations of process design and operation are necessary to maximize yield, quality, and consistency in the production of these complex therapeutic molecules. As larger, more complex proteins became targets for production, it became apparent that mammalian cells could carry out some aspects of molecular processing more efficiently than bacteria or the protein chemist. In general, current mammalian cell production systems secrete the protein of interest. The most direct confirmation of genetic stability of the host cell would be to determine the gene sequence at various stages before, during, and after the anticipated production life. Additional evidence of genetic stability can be obtained by determining whether the cells retain consistent morphology, growth characteristics, and nutritional status throughout the production lifetime.