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De Leiris N, Perret P, Lombardi C, Gözel B, Chierici S, Millet P, Debiossat M, Bacot S, Tournier BB, Chames P, Lenormand JL, Ghezzi C, Fagret D, Moulin M. A single-domain antibody for the detection of pathological Tau protein in the early stages of oligomerization. J Transl Med 2024; 22:163. [PMID: 38365700 PMCID: PMC10870657 DOI: 10.1186/s12967-024-04987-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Accepted: 02/12/2024] [Indexed: 02/18/2024] Open
Abstract
BACKGROUND Soluble oligomeric forms of Tau protein have emerged as crucial players in the propagation of Tau pathology in Alzheimer's disease (AD). Our objective is to introduce a single-domain antibody (sdAb) named 2C5 as a novel radiotracer for the efficient detection and longitudinal monitoring of oligomeric Tau species in the human brain. METHODS The development and production of 2C5 involved llama immunization with the largest human Tau isoform oligomers of different maturation states. Subsequently, 2C5 underwent comprehensive in vitro characterization for affinity and specificity via Enzyme-Linked Immunosorbent Assay and immunohistochemistry on human brain slices. Technetium-99m was employed to radiolabel 2C5, followed by its administration to healthy mice for biodistribution analysis. RESULTS 2C5 exhibited robust binding affinity towards Tau oligomers (Kd = 6.280 nM ± 0.557) and to Tau fibers (Kd = 5.024 nM ± 0.453), with relatively weaker binding observed for native Tau protein (Kd = 1791 nM ± 8.714) and amyloid peptide (Kd > 10,000 nM). Remarkably, this SdAb facilitated immuno-histological labeling of pathological forms of Tau in neurons and neuritic plaques, yielding a high-contrast outcome in AD patients, closely mirroring the performance of reference antibodies AT8 and T22. Furthermore, 2C5 SdAb was successfully radiolabeled with 99mTc, preserving stability for up to 6 h post-radiolabeling (radiochemical purity > 93%). However, following intravenous injection into healthy mice, the predominant uptake occurred in kidneys, amounting to 115.32 ± 3.67, 97.70 ± 43.14 and 168.20 ± 34.52% of injected dose per gram (% ID/g) at 5, 10 and 45 min respectively. Conversely, brain uptake remained minimal at all measured time points, registering at 0.17 ± 0.03, 0.12 ± 0.07 and 0.02 ± 0.01% ID/g at 5, 10 and 45 min post-injection respectively. CONCLUSION 2C5 demonstrates excellent affinity and specificity for pathological Tau oligomers, particularly in their early stages of oligomerization. However, the current limitation of insufficient blood-brain barrier penetration necessitates further modifications before considering its application in nuclear medicine imaging for humans.
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Affiliation(s)
- Nicolas De Leiris
- University Grenoble Alpes, Clinique Universitaire de Médecine Nucléaire, INSERM, Centre Hospitalier Universitaire Grenoble Alpes, LRB, CS 10217, 38043, Grenoble CEDEX 9, France.
| | - Pascale Perret
- University Grenoble Alpes, INSERM, LRB, 38000, Grenoble, France
| | | | - Bülent Gözel
- University Grenoble Alpes, INSERM, LRB, 38000, Grenoble, France
| | - Sabine Chierici
- University Grenoble Alpes, CNRS, DCM, 38000, Grenoble, France
| | - Philippe Millet
- Division of Adult Psychiatry, Department of Psychiatry, Geneva University Hospitals, Geneva, Switzerland
| | | | - Sandrine Bacot
- University Grenoble Alpes, INSERM, LRB, 38000, Grenoble, France
| | - Benjamin B Tournier
- Division of Adult Psychiatry, Department of Psychiatry, Geneva University Hospitals, Geneva, Switzerland
| | - Patrick Chames
- Aix Marseille University, CNRS, INSERM, Institut Paoli-Calmettes, CRCM, Marseille, France
| | | | | | - Daniel Fagret
- University Grenoble Alpes, INSERM, LRB, 38000, Grenoble, France
| | - Marcelle Moulin
- University Grenoble Alpes, INSERM, LRB, 38000, Grenoble, France
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Aguero C, Dhaynaut M, Amaral AC, Moon SH, Neelamegam R, Scapellato M, Carazo-Casas C, Kumar S, El Fakhri G, Johnson K, Frosch MP, Normandin MD, Gómez-Isla T. Head-to-head comparison of [ 18F]-Flortaucipir, [ 18F]-MK-6240 and [ 18F]-PI-2620 postmortem binding across the spectrum of neurodegenerative diseases. Acta Neuropathol 2024; 147:25. [PMID: 38280071 PMCID: PMC10822013 DOI: 10.1007/s00401-023-02672-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 12/19/2023] [Accepted: 12/19/2023] [Indexed: 01/29/2024]
Abstract
We and others have shown that [18F]-Flortaucipir, the most validated tau PET tracer thus far, binds with strong affinity to tau aggregates in Alzheimer's (AD) but has relatively low affinity for tau aggregates in non-AD tauopathies and exhibits off-target binding to neuromelanin- and melanin-containing cells, and to hemorrhages. Several second-generation tau tracers have been subsequently developed. [18F]-MK-6240 and [18F]-PI-2620 are the two that have garnered most attention. Our recent data indicated that the binding pattern of [18F]-MK-6240 closely parallels that of [18F]-Flortaucipir. The present study aimed at the direct comparison of the autoradiographic binding properties and off-target profile of [18F]-Flortaucipir, [18F]-MK-6240 and [18F]-PI-2620 in human tissue specimens, and their potential binding to monoamine oxidases (MAO). Phosphor-screen and high resolution autoradiographic patterns of the three tracers were studied in the same postmortem tissue material from AD and non-AD tauopathies, cerebral amyloid angiopathy, synucleopathies, transactive response DNA-binding protein 43 (TDP-43)-frontotemporal lobe degeneration and controls. Our results show that the three tracers show nearly identical autoradiographic binding profiles. They all strongly bind to neurofibrillary tangles in AD but do not seem to bind to a significant extent to tau aggregates in non-AD tauopathies pointing to their limited utility for the in vivo detection of non-AD tau lesions. None of them binds to lesions containing β-amyloid, α-synuclein or TDP-43 but they all show strong off-target binding to neuromelanin and melanin-containing cells, as well as weaker binding to areas of hemorrhage. The autoradiographic binding signals of the three tracers are only weakly displaced by competing concentrations of selective MAO-B inhibitor deprenyl but not by MAO-A inhibitor clorgyline suggesting that MAO enzymes do not appear to be a significant binding target of any of them. These findings provide relevant insights for the correct interpretation of the in vivo behavior of these three tau PET tracers.
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Affiliation(s)
- Cinthya Aguero
- MassGeneral Institute for NeuroDegenerative Disease, Charlestown, MA, USA
- Department of Neurology, Massachusetts General Hospital, WACC Suite 715, 15th Parkman St., Boston, MA, 02114, USA
| | - Maeva Dhaynaut
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
| | - Ana C Amaral
- MassGeneral Institute for NeuroDegenerative Disease, Charlestown, MA, USA
- Department of Neurology, Massachusetts General Hospital, WACC Suite 715, 15th Parkman St., Boston, MA, 02114, USA
| | - S-H Moon
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
| | - Ramesh Neelamegam
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
| | - Margaret Scapellato
- MassGeneral Institute for NeuroDegenerative Disease, Charlestown, MA, USA
- Department of Neurology, Massachusetts General Hospital, WACC Suite 715, 15th Parkman St., Boston, MA, 02114, USA
| | - Carlos Carazo-Casas
- MassGeneral Institute for NeuroDegenerative Disease, Charlestown, MA, USA
- Department of Neurology, Massachusetts General Hospital, WACC Suite 715, 15th Parkman St., Boston, MA, 02114, USA
| | - Sunny Kumar
- MassGeneral Institute for NeuroDegenerative Disease, Charlestown, MA, USA
- Department of Neurology, Massachusetts General Hospital, WACC Suite 715, 15th Parkman St., Boston, MA, 02114, USA
| | - Georges El Fakhri
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
| | - Keith Johnson
- Department of Neurology, Massachusetts General Hospital, WACC Suite 715, 15th Parkman St., Boston, MA, 02114, USA
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
| | - Matthew P Frosch
- MassGeneral Institute for NeuroDegenerative Disease, Charlestown, MA, USA
- Department of Neurology, Massachusetts General Hospital, WACC Suite 715, 15th Parkman St., Boston, MA, 02114, USA
- C.S. Kubik Laboratory for Neuropathology, Massachusetts General Hospital, Boston, MA, USA
| | - Marc D Normandin
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
| | - Teresa Gómez-Isla
- MassGeneral Institute for NeuroDegenerative Disease, Charlestown, MA, USA.
- Department of Neurology, Massachusetts General Hospital, WACC Suite 715, 15th Parkman St., Boston, MA, 02114, USA.
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López-González FJ, Costoya-Sánchez A, Paredes-Pacheco J, Moscoso A, Silva-Rodríguez J, Aguiar P. Impact of spill-in counts from off-target regions on [ 18F]Flortaucipir PET quantification. Neuroimage 2022; 259:119396. [PMID: 35753593 DOI: 10.1016/j.neuroimage.2022.119396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 05/23/2022] [Accepted: 06/15/2022] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND [18F]Flortaucipir (FTP) PET quantification is usually hindered by spill-in counts from off-target binding (OFF) regions. The present work aims to provide an in-depth analysis of the impact of OFF in FTP PET quantification, as well as to identify optimal partial volume correction (PVC) strategies to minimize this problem. METHODS 309 amyloid-beta (Aβ) negative cognitively normal subjects were included in the study. Additionally, 510 realistic FTP images with different levels of OFF were generated using Monte Carlo simulation (MC). Images were corrected for PVC using both a simple two-compartment and a multi-region method including OFF regions. FTP standardized uptake value ratio (SUVR) was quantified in Braak Areas (BA), the hippocampus (which was not included in Braak I/II) and different OFF regions (caudate, putamen, pallidum, thalamus, choroid plexus (ChPlex), cerebellar white matter (cerebWM), hemispheric white matter (hemisWM) and cerebrospinal fluid (CSF)) using the lower portion of the cerebellum as a reference region. The correlations between OFF and cortical SUVRs were studied both in real and in simulated PET images, with and without PVC. RESULTS In-vivo, we found correlations between all OFF and target regions, especially strong for the hemisWM (slope>0.63, R2>0.4). All the correlations were attenuated but remained significant after applying PVC, except for the ChPlex. In MC simulations, the hemisWM and CSF were the main contributors to PVE in all BA (slopes 0.15-0.26 and 0.13-0.21 respectively). The hemisWM (slope=0.2), as well as the ChPlex (slope=0.02), influenced SUVRs in the hippocampus. The CerebWM was negatively correlated with all target regions (slope<-0.02, R2>0.8). While no other correlations between OFF and target regions were found, hemisWM was correlated with all OFF regions but the cerebWM (slopes 0.06-0.33). HemisWM correlations attenuated (slopes<0.06) when applying two-compartment PVC, but the hippocampus-ChPlex and the cerebWM correlations required more complex PVC with dedicated compartments for these regions. In-vivo, PVC removed a notably higher fraction of the correlation between OFF regions found to be affected by PVE in the simulation studies and BA (≈50%) than for OFF regions not affected by PVE (16%). CONCLUSION HemisWM is the main driver of spill-in effects in FTP PET, affecting both target regions and the rest of OFF regions. PVC successfully reduces PVE, even when using a simple two-compartment method. Despite PVC, non-zero correlations were still observed between target and OFF regions in vivo, which suggests the existence of biological or tracer-related contributions to these correlations.
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Affiliation(s)
- Francisco J López-González
- Molecular Imaging Group, Department of Radiology, Faculty of Medicine and Center for Research in Molecular Medicine and Chronic Diseases (CIMUS), University of Santiago de Compostela (USC), Campus Vida, Santiago de Compostela, Galicia, Spain; Molecular Imaging Unit (UIM), Centro de Investigaciones Médico-Sanitarias (CIMES), General Foundation of the University of Málaga (Fguma), Málaga, Spain
| | - Alejandro Costoya-Sánchez
- Molecular Imaging Group, Department of Radiology, Faculty of Medicine and Center for Research in Molecular Medicine and Chronic Diseases (CIMUS), University of Santiago de Compostela (USC), Campus Vida, Santiago de Compostela, Galicia, Spain; Nuclear Medicine Department and Molecular Imaging Group, University Hospital CHUS-IDIS, Travesía da Choupana s/n, Santiago de Compostela, 15706, Spain
| | - José Paredes-Pacheco
- Molecular Imaging Group, Department of Radiology, Faculty of Medicine and Center for Research in Molecular Medicine and Chronic Diseases (CIMUS), University of Santiago de Compostela (USC), Campus Vida, Santiago de Compostela, Galicia, Spain; Molecular Imaging Unit (UIM), Centro de Investigaciones Médico-Sanitarias (CIMES), General Foundation of the University of Málaga (Fguma), Málaga, Spain
| | - Alexis Moscoso
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, and The Wallenberg Centre for Molecular and Translational Medicine, University of Gothenburg, Gothenburg, Sweden
| | - Jesús Silva-Rodríguez
- Nuclear Medicine Department and Molecular Imaging Group, University Hospital CHUS-IDIS, Travesía da Choupana s/n, Santiago de Compostela, 15706, Spain; Movement Disorders Unit, Clinical Neurology and Neurophysiology Department, Institute of Biomedicine of Seville, Virgen del Rocío University Hospital/CSIC/University of Seville, Seville, Spain.
| | - Pablo Aguiar
- Molecular Imaging Group, Department of Radiology, Faculty of Medicine and Center for Research in Molecular Medicine and Chronic Diseases (CIMUS), University of Santiago de Compostela (USC), Campus Vida, Santiago de Compostela, Galicia, Spain; Nuclear Medicine Department and Molecular Imaging Group, University Hospital CHUS-IDIS, Travesía da Choupana s/n, Santiago de Compostela, 15706, Spain
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