High-specificity antibodies and detection methods for quantifying phosphorylated tau from clinical samples

Abstract

The ability to measure total and phosphorylated tau levels in clinical samples is transforming the detection of Alzheimer's disease (AD) and other neurodegenerative diseases. In particular, recent reports indicate that accurate detection of low levels of phosphorylated tau (p-tau) in plasma provides a reliable biomarker of AD long before sensing memory loss. Therefore, the diagnosis and monitoring of neurodegenerative diseases progression using blood samples is becoming a reality. These major advances were achieved by using antibodies specific to p-tau as well as sophisticated high-sensitivity immunoassay platforms. This review focuses on these enabling advances in high-specificity antibody development, engineering, and novel signal detection methods. We will draw insights from structural studies on p-tau antibodies, engineering efforts to improve their binding properties, and efforts to validate their specificity. A comprehensive survey of high-sensitivity p-tau immunoassay platforms along with sensitivity limits will be provided. We conclude that although robust approaches for detecting certain p-tau species have been established, systematic efforts to validate antibodies for assay development is still needed for the recognition of biomarkers for AD and other neurodegenerative diseases.

Keywords: Alzheimer’s disease; antibody specificity; antibody validation; neurodegeneration; phosphorylated tau.

Figure 1

Structural analysis of p-tau antibodies. Each panel is labeled with the corresponding PDB ID, name of antibody clone, and phospho-site recognized by the antibody. The panels were generated using CCP4MG [91]. Antibody complementarity determining regions L1-3 and H1-3 that interact with the p-tau peptide are indicated. The lower half of each panel shows surface charge (blue—positive, red—negative). The phosphorus in the phosphate group is indicated in magenta. Antibodies in panels (a-b) are not specific to p-tau. Antibodies in panels (c–f) interact with a single phosphorylated residue. Antibodies in panel (g) interact with three phosphorylated residues.