Recombinant proteins, quality control

Host Cell Impurities Various organisms have been used to produce recombinant proteins yeast, bacteria (e.g., E. coli), insect cells, and mammalian cells such as Chinese hamster ovary (CHO) cells. During the purification process, some HCPs can copurify with the protein product. Because of the specificity of the antigen-antibody interaction, an ELISA can be used to detect and quantitate the contaminating HCPs. Detecting host impurities is important for quality process control as well as for product safety issues. The intent is to avoid unsafe levels of residual HCPs which might lead to adverse reactions.11... 

In order to verify the molecular and functional characteristics of the protein synthesized by the expression system, a number of molecular tools have been developed. These tools have been optimized over the years to allow efficient verification of the molecular characteristics of recombinant proteins. Some are also used for quality control procedures in the synthesis of recombinant proteins for pharmaceutical use. 

The use of CE methods for routine quality control of synthetic or recombinant peptides-proteins necessitates optimization strategies for rapid method development. Ideally, the methods should be simple, fast, and robust. Because capillary electrophoresis in the zone format is the most simplistic, initial efforts should be directed toward the use of a simple buffer system [61]. The high efficiency and reproducibility in protein-pep-tide separations demands that interactions between the analyte and capillary wall be neglible. The use of low-pH buffers generally results in enhanced reproduciblity, and hence ruggedness, as slight variations in the capillary surface will have little impact on the already suppressed EOF. 

In general, the production of good MAbs depends to a large part upon the quality, purity and availability of antigen. In the production of the anti-RANTES chemokine monoclonal antibodies described here, a pET-3 E. coli expression system was used that allowed the manufacture of large quantities of recombinant human RANTES protein (see Notes 1,2, and 3). The recombinant protein was also used as a positive control in Western and immunoprecipitation experiments performed at later stages of the characterization of the MAbs (1). 

The protein molecular mass is insufficient information for identification, but it is adequate to confirm identity therefore, MS is one of the preferred techniques for characterization and quality control of recombinant proteins and other biomolecules. In the same way, it has been used to study posttranslational modifications (like glycosylation and disulfide bonding pattern), and other processes that can modify protein mass.11... 

Carbohydrate-specific hepatic receptor-mediated clearance mechanisms include the asialoglycoprotein, S04-GalNAc and Man receptors [235,236]. The asialoglycoprotein receptor on liver hepatocytes is most significant and accounts for the short circulatory half-life of proteins lacking terminal SA [237]. Reliable quantitative analysis of SA will be an important aspect of quality control for glycoprotein pharmaceuticals. For glycoproteins produced in recombinant S. cerevisiae and insect cells which possess terminal Man or Gn moieties, the Man receptor presumably represents a major clearance mechanism [229]. 

Electronspray ionization(ESI) MS Useful in quality control for recombinant proteins and site analysis of tryptic glycopeptides. Readily interfaced with HPLC or CE systems. It can differentiate between 0- and IV-linked glycans, and also between complex, hybrid or high mannose forms [275]... 

Peptide Mapping. Peptide mapping is an important tool for protein identif-ication, primary structure determination, the detection of posttranslational modifications, the identification of genetic variants, and the determination of glycosylation and/or disulfide sites. For these reasons, peptide mapping is widely used for quality control and for the characterization of recombinant DNA-derived products. Moreover, the high resolution of CE makes it a powerful peptide mapping technique. 

---