Non-Phosphorylated Tau as a Potential Biomarker of Alzheimer’s Disease: Analytical and Diagnostic Characterization

Article type: Research Article

Authors: Lewczuk, Piotr^{a; j; *} | Lelental, Natalia^a | Lachmann, Ingolf^b | Holzer, Max^c | Flach, Katharina^b | Brandner, Sebastian^d | Engelborghs, Sebastiaan^e | Teunissen, Charlotte E.^f | Zetterberg, Henrik^{g; h} | Molinuevo, José Luisⁱ | Mroczko, Barbara^j | Blennow, Kaj^g | Popp, Julius^k | Parnetti, Lucilla^l | Chiasserini, Davide^l | Perret-Liaudet, Armand^m | Spitzer, Philipp^a | Maler, Juan Manuel^a | Kornhuber, Johannes^a

Affiliations: [a] Department of Psychiatry and Psychotherapy, Universitätsklinikum Erlangen, and Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany | [b] AJ Roboscreen GmbH, Leipzig, Germany | [c] Paul Flechsig Institute of Brain Research, University of Leipzig, Germany | [d] Department of Neurosurgery, Universitätsklinikum Erlangen, and Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany | [e] Reference Center for Biological Markers of Dementia (BIODEM), Institute Born-Bunge, University of Antwerp, Antwerp, and Department of Neurology and Memory Clinic, Hospital Network Antwerp (ZNA) Middelheim and Hoge Beuken, Antwerp, Belgium | [f] Neurochemistry Laboratory and Biobank, Department of Clinical Chemistry, Neuroscience Campus Amsterdam, VU University Medical Center, Amsterdam, The Netherlands | [g] Clinical Neurochemistry Laboratory, Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, the Sahlgrenska Academy at the University of Gothenburg, Mölndal, Sweden | [h] Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London, UK | [i] Alzheimer’s Disease and Other Cognitive Disorders Unit, Hospital Clinic, IDIBAPS, Barcelona, Spain | [j] Department of Neurodegeneration Diagnostics, Medical University of Białystok, and Department of Biochemical Diagnostics, University Hospital of Białystok, Białystok, Poland | [k] Service of Old Age Psychiatry, Department of Psychiatry, University Hospital of Lausanne, Switzerland | [l] Laboratory of Clinical Neurochemistry, Department of Medicine, Section of Neurology, University of Perugia, Perugia, Italy | [m] Hospices Civils de Lyon, Groupement Hospitalier Est, Biochemistry Department, Neurochemistry unit; Lyon University, Lyon Neuroscience Research Center, INSERM U1028, CNRS UMR 5292, BioRaN Team, Bron Cedex, France

Correspondence: [*] Correspondence to: Prof. Dr. med. Piotr Lewczuk, Lab for Clinical Neurochemistry and Neurochemical Dementia Diagnostics, Department of Psychiatry and Psychotherapy, Schwabachanlage 6, 91054 Erlangen, Germany. Tel.: +49 9131 85 34324; Fax: +49 9131 85 34 238; E-mail: Piotr.Lewczuk@uk-erlangen.de.

Abstract: Background: Virtually nothing is known about a potential diagnostic role of non-phospho-epitopes of Tau (Non-P-Tau) in cerebrospinal fluid (CSF). Objective: To establish and analytically and clinically characterize the first assay capable to measure concentrations of Non-P-Tau in human CSF. Methods: An antibody (1G2) was developed that selectively binds to the Tau molecule non-phosphorylated at the positions T175 and T181, and was used in establishing a sandwich ELISA capable to measure Non-P-Tau in human CSF, following analytical and clinical validation of the method. Results: The 1G2 antibody shows decreasing reactivity to tau peptides containing phosphorylation mainly at positions T175 and T181. Detection limit of the assay is 25 pg/ml; the coefficients of variation (CVs) of the optical densities of the repeated standard curves were between 3.6–15.9%. Median intra-assay imprecision of double measurements was 4.8%; inter-assay imprecision was in the range of 11.2% – 15.3%. Non-P-Tau concentrations are stable in the CSF samples sent to distinct laboratories under ambient temperature; inter-laboratory variation was approximately 30%. The Non-P-Tau CSF concentrations were highly significantly increased in patients with Alzheimer’s disease in stage of mild cognitive impairment or dementia (AD/MCI, n = 58, 109.2±32.0 pg/mL) compared to the non-demented Controls (n = 42, 62.1±9.3 pg/mL, p < 0.001). At the cut-off of 78.3 pg/mL, the sensitivity and the specificity were 94.8% and 97.6%, respectively. Conclusion: For the first time, an assay is reported to reliably measure concentrations of non-phosphorylated Tau in human CSF.

Keywords: Biomarkers, cerebrospinal fluid, phosphorylation, tau

DOI: 10.3233/JAD-160448

Journal: Journal of Alzheimer's Disease, vol. 55, no. 1, pp. 159-170, 2017