Residual host cell proteins

Lupker, J. H. Residual host cell protein from continuous cell lines. Dev Bio Stand 93 61-64 (1998). 

Lupker JH (1998), Residual host cell protein from continuous cell lines effect on the safety of protein pharmaceuticals, In Brown F, Griffths E, Horaud F, Petricciani JC (Eds) Safety of Biological Products Prepared from Mammalian Cell Culture, vol. 93, Dev. Biol. Stand., Karger, Basel, pp. 61 -64. 

Typically, biotechnology products have been produced in cell lines not of human origin. In such cases, residual host cell proteins (HCP) are perceived as a safety concern to the patient. In the case of... 

DEVELOPMENT AND OPTIMIZATION OF A QUANTITATIVE WESTERN BLOT AND DOT BLOT PROCEDURE FOR THE DETERMINATION OF RESIDUAL HOST CELL PROTEINS PRESENT IN INACTIVATED POLIO VACCINE USING A GZU BASED SIGNAL REAGENT... 

Analytical Techniques and Release Specifications of Bulk Virus Lots. The crude viral harvest was tested for adventitious agents as needed to comply with current regulatory guidelines. Purified virus was tested to confirm the absence of RCAs, residual host cell proteins and DNA, and endotoxin, and to quantify total and infectious vector particles and, thus, the infectivity ratio. Bulk virus lots were released after meeting specifications, which included <1 endotoxin unit/mL and infectivity ratios of >2% (infectious titer/total viral particles). 

Dagouassat, N., Haeuw, J.F., Robillard, V., Damien, F., Libon, C., Corvaia, N., Lawny, F., Nguyen, T.N., Bomiefoy, J.Y. and Beck, A., 2001a, Development of a quantitative assay for residual host cell proteins in a recombinant subunit vaccine against human respiratory syncytial virus. J. Immunol. Methods 251 151-159. 

Polishing final purification step (invariably using chromatography) to remove dose product-related impurities, residual of host cell proteins (HCPs) and endotoxins. 

Of these molecular variants, one is the desired product with the desired properties with respect to biological activity and efficacy. Some structurally related variants (referred to as product related ) exhibit similar properties to the desired product and are therefore not considered as impurities. However, there may also be structurally related variants with altered properties with respect to biological activity, efficacy and/ or safety, which must be considered as impurities. In addition to the molecular variants of the protein (or protein-like) product, additional process-related substances may be part of a biotechnological drug substance, e.g., cell culture media, host cell proteins, DNA residuals, solvents, bacteria and/or viruses. This suggests that the determination of purity of these products (which is referred to as purity estimation rather than purity determination ) is a complex analytical issue. A purity estimation consists of both the definition of the heterogeneity of the protein (or proteinlike) product, and the identification and quantitation of product- and process-re-... 

Table 3. Residual content of is. coli OmpA and host cell proteins in pilot batches of P40. P40 bulks E. coli OmpA contend HCP contend...

In addition to binding to sialic acid residues of the carbohydrate side chains of cellular proteins that the virus exploits as receptors, hemagglutinin has a second function in the infection of host cells. Viruses, bound to the plasma membrane via their membrane receptors, are taken into the cells by endocytosis. Proton pumps in the membrane of endocytic vesicles that now contain the bound viruses cause an accumulation of protons and a consequent lowering of the pH inside the vesicles. The acidic pH (below pH 6) allows hemagglutinin to fulfill its second role, namely, to act as a membrane fusogen by inducing the fusion of the viral envelope membrane with the membrane of the endosome. This expels the viral RNA into the cytoplasm, where it can begin to replicate. 

The infectious cycle of a (+)-strand RNA virus such as the hepatitis C virus differs by the fate of the viral RNA genome in the infected cell. Upon entry into the cell, the HCV genome is used as a messenger RNA to drive the synthesis of a large polyprotein precursor of about 3,000 residues [2]. The structural proteins are excised from the precursor by host cell signal peptidase. 

Of all the possible contaminants and impurities of a biopharmaceutical product, organisms (bacteria, virus, mycoplasma) and their products (DNA, endotoxin, host protein), media components, and raw materials, it is most appropriate to use an ELISA for the HCP impurities and some of the process residuals (media components and raw materials). Impurities from media components are known or expected unlike those from the host cell. 

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... 

Cell Culture-Derived Media-Derived Protein Impurities. Immunoassays can detect low impurity levels (<1 ppm).4 The ELISA is probably one of the most sensitive analytical methods. If bovine serum is used as a media component, then testing should include ELISAs for bovine serum albumin (BSA), bovine transferrin, bovine fetuin, and bovine IgG. Often hormones and growth factors, such as insulin or insulinlike growth factor, are used as media components. ELISAs should be used to detect and quantitate these residuals in the various production steps as well as in the final product. There are commercially available antibodies to most commonly used media components. If proprietary media components are used, then the same investment in time and effort is required for the production of specific antibodies, as described above for host cell impurities. 

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