In Vivo Detection of Amyloid-\(\beta\) Deposits Using Heavy Chain Antibody Fragments in a Transgenic Mouse Model for Alzheimer's Disease

This study investigated the in vivo properties of two heavy chain antibody fragments (VHH), ni3A and pa2H, to differentially detect vascular or parenchymal amyloid-b deposits characteristic for Alzheimer’s disease and cerebral amyloid angiopathy. Blood clearance and biodistribution including brain uptake were assessed by bolus injection of radiolabeled VHH in APP/PS1 mice or wildtype littermates. In addition, in vivo specificity for Ab was examined in more detail with fluorescently labeled VHH by circumventing the blood-brain barrier via direct application or intracarotid co-injection with mannitol. All VHH showed rapid renal clearance (10–20 min). Twenty-four hours post-injection Tc-pa2H resulted in a small yet significant higher cerebral uptake in the APP/PS1 animals. No difference in brain uptake were observed for Tc-ni3A or DTPA(In)pa2H, which lacked additional peptide tags to investigate further clinical applicability. In vivo specificity for Ab was confirmed for both fluorescently labeled VHH, where pa2H remained readily detectable for 24 hours or more after injection. Furthermore, both VHH showed affinity for parenchymal and vascular deposits, this in contrast to human tissue, where ni3A specifically targeted only vascular Ab. Despite a brain uptake that is as yet too low for in vivo imaging, this study provides evidence that VHH detect Ab deposits in vivo, with high selectivity and favorable in vivo characteristics, making them promising tools for further development as diagnostic agents for the distinctive detection of different Ab deposits. Citation: Nabuurs RJA, Rutgers KS, Welling MM, Metaxas A, de Backer ME, et al. (2012) In Vivo Detection of Amyloid-b Deposits Using Heavy Chain Antibody Fragments in a Transgenic Mouse Model for Alzheimer’s Disease. PLoS ONE 7(6): e38284. doi:10.1371/journal.pone.0038284 Editor: Gayle E. Woloschak, Northwestern University Feinberg School of Medicine, United States of America Received July 12, 2011; Accepted May 3, 2012; Published June 4, 2012 Copyright: 2012 Nabuurs et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: Research was supported by: (1) the Center for Translational Molecular Medicine, LeARN, http://www.ctmm.nl; (2) Innovatiegericht OnderzoeksProgramma (IOP)Genomics, IGE05005, http://www.agentschapnl.nl/nl/programmas-regelingen/iop-genomics; (3) the Center for Medical Systems Biology, CMSB2, http://www.cmsb.nl; and (4) The Netherlands Organisation for Scientific Research (NWO) Athena, 700.58.801, http://www.nwo.nl/nwohome.nsf/ pages/NWOA_6ZXCX3. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: [email protected] . These authors contributed equally to this work.