Non-Invasive Imaging of Amyloid Deposits in a Mouse Model of AGel Using 99mTc-Modified Nanobodies and SPECT/CT

Adriaan Verhelle; Wouter Van Overbeke; Cindy Peleman; Rebecca De Smet; Olivier Zwaenepoel; Tony Lahoutte; Jo Van Dorpe; Nick Devoogdt; Jan Gettemans

doi:10.1007/s11307-016-0960-y

Non-Invasive Imaging of Amyloid Deposits in a Mouse Model of AGel Using ^99mTc-Modified Nanobodies and SPECT/CT

Mol Imaging Biol. 2016 Dec;18(6):887-897. doi: 10.1007/s11307-016-0960-y.

Authors

Adriaan Verhelle¹, Wouter Van Overbeke¹, Cindy Peleman², Rebecca De Smet³, Olivier Zwaenepoel¹, Tony Lahoutte², Jo Van Dorpe³, Nick Devoogdt², Jan Gettemans⁴

Affiliations

¹ Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Albert Baertsoenkaai 3, B-9000, Ghent, Belgium.
² In Vivo Cellular and Molecular Imaging Laboratory, Vrije Universiteit Brussel, Brussels, Belgium.
³ Department of Medical and Forensic Pathology, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium.
⁴ Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Albert Baertsoenkaai 3, B-9000, Ghent, Belgium. jan.gettemans@ugent.be.

PMID: 27130233
DOI: 10.1007/s11307-016-0960-y

Abstract

Purpose: Gelsolin amyloidosis (AGel), also known as familial amyloidosis, Finnish type (FAF), is an autosomal, dominant, incurable disease caused by a point mutation (G654A/T) in the gelsolin (GSN) gene. The mutation results in loss of a Ca²⁺-binding site in the second gelsolin domain. Subsequent incorrect folding exposes a cryptic furin cleavage site, leading to the formation of a 68-kDa C-terminal cleavage product (C68) in the trans-Golgi network. This C68 fragment is cleaved by membrane type 1-matrix metalloproteinase (MT1-MMP) during secretion into the extracellular environment, releasing 8- and 5-kDa amyloidogenic peptides. These peptides aggregate and cause disease-associated symptoms. We set out to investigate whether AGel-specific nanobodies could be used to monitor amyloidogenic gelsolin buildup.

Procedures: Three nanobodies (FAF Nb1-3) raised against the 8-kDa fragment were screened as AGel amyloid imaging agents in WT and AGel mice using ^99mTc-based single-photon emission computed tomography (SPECT)/X-ray tomography (CT), biodistribution analysis, and immunofluorescence (IF). The quantitative characteristics were analyzed in a follow-up study with a Nb11-expressing mouse model.

Results: All three nanobodies possess the characteristics desired for a ^99mTc-based SPECT/CT imaging agent, high specificity and a low background signal. FAF Nb1 was identified as the most potent, based on its superior signal-to-noise ratio and signal specificity. As a proof of concept, we implemented ^99mTc-FAF Nb1 in a follow-up study of the Nb11-expressing AGel mouse model. Using biodistribution analysis and immunofluorescence, we demonstrated the validity of the data acquired via ^99mTc-FAF Nb1 SPECT/CT.

Conclusion: These findings demonstrate the potential of this nanobody as a non-invasive tool to image amyloidogenic gelsolin deposition and assess the therapeutic capacity of AGel therapeutics currently under development. We propose that this approach can be extended to other amyloid diseases, thereby contributing to the development of specific therapies.

Keywords: AGel; Gelsolin; Nanobody; SPECT; VHH.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Amyloid / metabolism*
Amyloidosis, Familial / diagnostic imaging*
Animals
Antibody Specificity / immunology
Binding Sites
Disease Models, Animal
Fluorescent Antibody Technique
Gelsolin / chemistry
Mice, Inbred C57BL
Muscle, Skeletal / metabolism
Muscle, Skeletal / pathology
Myocardium / metabolism
Myocardium / pathology
Signal-To-Noise Ratio
Single-Domain Antibodies / chemistry*
Staining and Labeling
Technetium / chemistry*
Tissue Distribution
Tomography, Emission-Computed, Single-Photon*
Tomography, X-Ray Computed*

Substances

Amyloid
Gelsolin
Single-Domain Antibodies
Technetium