Host cell protein testing by ELISAs and the use of orthogonal methods

• Published in: Biotechnology and bioengineering Vol. 111; no. 12; pp. 2367 - 2379
• Main Authors: Zhu-Shimoni, Judith, Yu, Christopher, Nishihara, Julie, Wong, Robert M., Gunawan, Feny, Lin, Margaret, Krawitz, Denise, Liu, Peter, Sandoval, Wendy, Vanderlaan, Martin
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.12.2014; Wiley Subscription Services, Inc
• Subjects: Animals; Antibodies; Antibodies - metabolism; antigen excess; Antigens; Assaying; Biotechnology; CHO Cells; Close packed lattices; Cricetinae; Cricetulus; Dilution; Electrophoresis, Gel, Two-Dimensional; ELISA; Enzyme-Linked Immunosorbent Assay - methods; Hexagonal cells; host cell proteins; linearity; Mass spectrometry; multi-analyte; orthogonal methods; Proteins; Proteins - analysis; Proteins - chemistry; Proteins - isolation & purification; Recombinant Proteins - metabolism; Research Design; Risk assessment; multi-analyte; orthogonal methods; host cell proteins; linearity; antigen excess; ELISA
• ISSN: 0006-3592; 1097-0290
• DOI: 10.1002/bit.25327

ABSTRACT Host cell proteins (HCPs) are among the process‐related impurities monitored during recombinant protein pharmaceutical process development. The challenges of HCP detection include (1) low levels of residual HCPs present in large excess of product protein, (2) the assay must measure a large number of different protein analytes, and (3) the population of HCP species may change during process development. Suitable methods for measuring process‐related impurities are needed to support process development, process validation, and control system testing. A multi‐analyte enzyme‐linked immunosorbent assay (ELISA) is the workhorse method for HCP testing due to its high throughput, sensitivity and selectivity. However, as the anti‐HCP antibodies, the critical reagents for HCP ELISA, do not comprehensively recognize all the HCP species, it is especially important to ensure that weak and non‐immunoreactive HCPs are not overlooked by the ELISA. In some cases limited amount of antibodies to HCP species or antigen excess causes dilution‐dependent non‐linearity with multi‐product HCP ELISA. In our experience, correct interpretation of assay data can lead to isolation and identification of co‐purifying HCP with the product in some cases. Moreover, even if the antibodies for a particular HCP are present in the reagent, the corresponding HCP may not be readily detected in the ELISA due to antibody/antigen binding conditions and availability of HCP epitopes. This report reviews the use of the HCP ELISA, discusses its limitations, and demonstrates the importance of orthogonal methods, including mass spectrometry, to complement the platform HCP ELISA for support of process development. In addition, risk and impact assessment for low‐level HCPs is also outlined, with consideration of clinical information. Biotechnol. Bioeng. 2014;111: 2367–2379. © 2014 Wiley Periodicals, Inc. CHOP levels tested by ELISAs decrease as the purification process steps progress and CHOP clearance is demonstrated at the end of the process. The CHOP ratio at each step is constant regardless of sample dilution. Exception of this dilution linearity is observed indicating co‐purifying CHOP that is not adequately detected by the ELISA. This can be depicted by a model of “antigen excess”. Application of orthogonal methods complement CHOP ELISAs to ensure co‐purifying CHOP species are detected and identified.