Immunoligand assay

Another antibody-based method is immunoligand assay (ILA) technology. The Threshold system (Molecular Devices, Sunnyvale, CA) shortens assay development and assay turnaround time.11 It adapts a sensitive detection system originally... 

Whitmire, M.L. and L.C. Eaton (1997). An immunoligand assay for quantitation of process specific Escherichia coli host cell contaminant proteins in a recombinant bovine somatotropin. J Immunoassay 18(1) 49-65. 

In addition to ELISA and Western blots for detecting host-cell protein impurities there is a third immunoassay now available to the bioanalyst for this purpose the immunoligand assay (ILA). Like the ELISA, it is configured as a double-antibody sandwich. The anti-host-cell protein antibodies are separately conjugated to biotin and to fluorescein. A tripartite immune complex is formed between host-cell protein impurities and these two anti-... 

This part will mainly focus on host cell proteins (HCPs) quantification. Process-specific HCP assays are in general targeted to be in place prior to the initiation of phase III clinical trials. Immunoassays are the most specific and sensitive techniques available for detecting and quantifying protein impurities. There are two methods commonly employed to quantify protein impurities in biopharmaceuticals enzyme-linked immunosorbent assays (ELISA) and immunoligand assays (ILA). Both methods are able to detect very low ppm level of impurities. ELISA have been developed to measure host protein impurities in a number of recombinant proteins including human growth hormone (Anicetti et ah, 1986), insulin (Baker et al, 1981) and staphylokinase (Wan et ah, 2002). ILA assays have been used to detect protein impurities in recombinant bovine somatotropin (Whitmire and Eaton,... 

Figure 6. Immunoligand assay reaction scheme, (reprinted with permission from Molecular Devices).

Figure 7. Representative HCP immunoligand assay standard curve.

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