One method used to diagnose (or monitor) common inflammatory disorders, such as ulcerative colitis and Crohn’s disease, is to measure the amount of the protein calprotectin in stool samples. In addition, the amount of calprotectin in serum levels can be used to monitor the inflammation status in rheumatoid arthritis
To do this, the calprotectin concentrations in patient samples are typically determined using antibodies that bind and detect the protein. For example, in lateral flow assays. But the results can vary depending on the type of antibody and assay used.
Now, researchers may have found a possible solution, which is to use peptides instead of antibodies to detect and measure disease markers like calprotectin. The teams at the company BÜHLMAN, and École polytechnique fédérale de Lausanne (EPFL) in Switzerland, developed a peptide, which is the first synthetic affinity reagent that could be generated against the biomarker calprotectin.
This research is published in Nature Communications in the paper, “High-affinity peptides developed against calprotectin and their application as synthetic ligands in diagnostic assays.”
Peptides can bind to proteins with high affinity and selectivity, but, unlike antibodies, they can be chemically produced with high purity and homogeneity. In addition, peptides are stable over time, cheaper to produce than antibodies and with lower inter-batch variability, and can be attached to a specific location on a surface, significantly simplifying diagnostic assay development because it allows for a more accurate and controlled way of detecting biomarkers.
The team at BÜHLMANN collaborated with the laboratory of Christian Heinis, PhD, professor at EPFL, to develop human calprotectin ligands based on peptides. From a library of more than 500 billion different peptides, Cristina Diaz-Perlas, PhD, a postdoc in Heinis’s group, isolated several binders of calprotectin, and showed that the peptides are suited for calprotectin quantification in simplified lateral flow assays. The best peptide had a dissociation constant of 26 nM, making it a candidate for diagnostic tests.
The peptide not only binds to a large surface region of calprotectin but also to a specific form of calprotectin that is the relevant species in patient samples. The team at BÜHLMANN tested the peptide in lateral flow cassettes and found that it was suited for accurate detection and quantification of calprotectin. In this proof-of-concept study, the setup was used to quantify the concentration of calprotectin in serum obtained from patient blood samples.
“The EPFL and BÜHLMANN teams are currently performing more tests with the calprotectin-specific peptide to translate the assay into a product that can bring the diagnostic power of this increasingly important biomarker to a new level to help patients suffering from inflammatory diseases,” said Heinis.