Identification of structural determinants on tau protein essential for its pathological function: novel therapeutic target for tau immunotherapy in Alzheimer's disease.

Eva Kontsekova,Branislav Kovacech,Rostislav Skrabana,Michal Novak,Norbert Zilka

doi:10.1186/alzrt277

Eva Kontsekova, Branislav Kovacech + Show 3 more

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https://doi.org/10.1186/alzrt277

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Journal: Alzheimer's research & therapy	Publication Date: Jan 1, 2014
Citations: 175	License type: cc-by

Affiliation: AXON Neuroscience (Slovakia)

Abstract

IntroductionPathologically modified tau protein is the main feature of Alzheimer’s disease (AD) and related tauopathies. Therefore, immunotherapies that target mis-disordered tau represent a promising avenue for the disease-modifying treatment of AD. In this report, we present our discovery of (1) a novel target for tau immunotherapy; (2) monoclonal antibody DC8E8, which neutralizes this target; and (3) the results of efficacy studies of DC8E8 in a murine model of tauopathy.MethodsIn vitro tau oligomerisation assays were used for the selection of antibodies. The therapeutic efficacy of DC8E8 was evaluated in transgenic mice. The structure of the DC8E8 epitope was determined by X-ray crystallography.ResultsScreening of a panel of monoclonal antibodies for their inhibitory activity in an in vitro pathological tau–tau interaction assay yielded DC8E8, which reduced the amount of oligomeric tau by 84%. DC8E8 recognised all developmental stages of tau pathology in AD human brains, including pretangles and intra- and extracellular tangles. Treatment with DC8E8 in a mouse AD model expressing mis-disordered human tau significantly reduced the amount of insoluble oligomerised tau and the number of early and mature neurofibrillary tangles in the transgenic mouse brains. By using a panel of tau-derived peptides in a competitive enzyme-linked immunosorbent assay, we identified the tau domain essential for pathological tau–tau interaction, which is targeted by DC8E8. The antibody was capable of binding to four highly homologous and yet independent binding regions on tau, each of which is a separate epitope. The X-ray structure of the DC8E8 Fab apo form, solved at 3.0 Å, suggested that the four DC8E8 epitopes form protruding structures on the tau molecule. Finally, by kinetic measurements with surface plasmon resonance, we determined that antibody DC8E8 is highly discriminatory between pathological and physiological tau.ConclusionsWe have discovered defined determinants on mis-disordered truncated tau protein which are responsible for tau oligomerisation leading to neurofibrillary degeneration. Antibody DC8E8 reactive with these determinants is able to inhibit tau–tau interaction in vitro and in vivo. DC8E8 is able to discriminate between the healthy and diseased tau proteome, making its epitopes suitable targets, and DC8E8 a suitable candidate molecule, for AD immunotherapy.

Highlights

Modified tau protein is the main feature of Alzheimer’s disease (AD) and related tauopathies
Discovery of these regions on tau is a prerequisite for the development of successful tau vaccines that will protect neurons from pathological tau–tau interaction. We identified such a common denominator, a domain on mis-disordered truncated tau that is essential for propagation of tau pathology, and we created a monoclonal antibody—DC8E8—that disables this function
DC8E8 candidate therapeutic antibody is inhibiting pathological tau–tau interactions In order to identify immunologically targetable structures on tau with therapeutic potential, we used an in vitro pathological tau–tau interaction assay to screen for Monoclonal antibody (mAb) with an inhibitory effect on pathological tau– tau interactions

Summary

Introduction

Modified tau protein is the main feature of Alzheimer’s disease (AD) and related tauopathies. Immunotherapies that target mis-disordered tau represent a promising avenue for the disease-modifying treatment of AD. Neurodegenerative foldopathies represent a group of human protein-misfolding disorders that are characterised by a pathological alteration in conformation of a native protein which makes it resistant to degradation and leads to pathological gain and loss of function. (5) Tau pathology in the absence of amyloid pathology strongly correlates with clinical features in human tauopathies such as progressive supranuclear palsy, corticobasal degeneration, tangle-only dementia, argyrophilic grain disease, frontotemporal dementia and Pick’s disease [15,16,17,18,19,20,21]. There is mounting scientific evidence supporting tau-targeted therapy. (1) Tau neurofibrillary pathology is the major correlate of clinical symptoms in AD [7,8,9]. (2) Distribution of neurofibrillary pathology defines subtypes of AD with distinct clinical characteristics [10]. (3) Neurofibrillary tangles (NFTs) precede amyloid-β pathology [11,12,13]. (4) Cortical atrophy measured by magnetic resonance imaging is associated with neurofibrillary pathology [14]. (5) Tau pathology in the absence of amyloid pathology strongly correlates with clinical features in human tauopathies such as progressive supranuclear palsy, corticobasal degeneration, tangle-only dementia, argyrophilic grain disease, frontotemporal dementia and Pick’s disease [15,16,17,18,19,20,21]. (6) Tau animal models reproduce neuronal and glial tau pathology leading to the progressive cognitive and/or motor impairment and premature death [5]

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