Sensitive detection of glucagon aggregation using amyloid fibril‐specific antibodies. Issue 8 (8th May 2019)

• Record Type: Journal Article
• Authors: Stimple, Samuel D.; Kalyoncu, Sibel; Desai, Alec A.; Mogensen, Jesper E.; Spang, Lotte T.; Asgreen, Désirée J.; Staby, Arne; Tessier, Peter M.
• Is Part Of: Biotechnology and bioengineering. Volume 116:Issue 8(2019)
• Page Start: 1868
• Page End: 1877
• Publication Date: 2019-05-08
• Subjects: aggregate -- antibody -- conformation -- directed evolution -- protein; Biotechnology -- Periodicals; Bioengineering -- Periodicals; 660.6
• DOI: 10.1002/bit.26994
• Languages: English
• ISSNs: 0006-3592

Abstract

Abstract: Sensitive detection of protein aggregates is important for evaluating the quality of biopharmaceuticals and detecting misfolded proteins in several neurodegenerative diseases. However, it is challenging to detect extremely low concentrations (<10 ppm) of aggregated protein in the presence of high concentrations of soluble protein. Glucagon, a peptide hormone used in the treatment of extreme hypoglycemia, is aggregation‐prone and forms amyloid fibrils. Detection of glucagon fibrils using conformation‐specific antibodies is an attractive approach for identifying such aggregates during process and formulation development. Therefore, we have used yeast surface display and magnetic‐activated cell sorting to sort single‐chain antibody libraries to identify antibody variants with high conformational specificity for glucagon fibrils. Notably, we find several high‐affinity antibodies that display excellent selectivity for glucagon fibrils, and we have integrated these antibodies into a sensitive immunoassay. Surprisingly, the sensitivity of our assay—which involves direct (nonantibody mediated) glucagon immobilization in microtiter plates—can be significantly enhanced by pretreating the microtiter plates with various types of globular proteins before glucagon immobilization. Moreover, increased total concentrations of glucagon peptide also significantly improve the sensitivity of our assay, which appears to be due to the strong seeding activity of immobilized fibrils at high glucagon concentrations. Our final assay is highly sensitive (fibril detection limit of ~0.5–1 ppm) and is >20 times more sensitive than detection using a conventional, amyloid‐specific fluorescent dye (Thioflavin T). We expect that this type of sensitive immunoassay can be readily integrated into the drug development process to improve the generation of safe and potent peptide therapeutics. Abstract : Sensitive detection of protein aggregates is important for evaluating the quality of biopharmaceuticals and detecting misfolded proteins in several neurodegenerative diseases. However, it is challenging to detect extremely low concentrations (<10 ppm) of aggregated protein in the presence of high concentrations of soluble protein. Glucagon, a peptide hormone used in the treatment of extreme hypoglycemia, is aggregation‐prone and forms amyloid fibrils. Conformation‐specific antibodies were generated that recognize glucagon fibrils in a highly selective manner, and these antibodies were integrated into an ELISA method that is >20 times more sensitive than conventional methods for detecting glucagon fibrils.