Development of a 64Cu-labeled CD4+ T cell targeting PET tracer: evaluation of CD4 specificity and its potential use in collagen-induced arthritis

Anne Skovsbo Clausen; Camilla Christensen; Esben Christensen; Sigrid Cold; Lotte Kellemann Kristensen; Anders Elias Hansen; Andreas Kjaer

doi:10.1186/s13550-022-00934-7

Development of a ⁶⁴Cu-labeled CD4⁺ T cell targeting PET tracer: evaluation of CD4 specificity and its potential use in collagen-induced arthritis

EJNMMI Res. 2022 Sep 16;12(1):62. doi: 10.1186/s13550-022-00934-7.

Authors

Anne Skovsbo Clausen¹, Camilla Christensen¹, Esben Christensen^{1

2}, Sigrid Cold^{1

3}, Lotte Kellemann Kristensen³, Anders Elias Hansen^{1

2}, Andreas Kjaer⁴

Affiliations

¹ Department of Clinical Physiology, Nuclear Medicine & PET and Cluster for Molecular Imaging, Department of Biomedical Sciences, Rigshospitalet and University of Copenhagen, Blegdamsvej 9, 2100, Copenhagen, Denmark.
² Department of Health Technology, Section for Biotherapeutic Engineering and Drug Targeting, Technical University of Denmark, Anker Engelunds Vej 1, 2800, Kongens Lyngby, Denmark.
³ Minerva Imaging, Lyshøjvej 21, 3650, Ølstykke, Denmark.
⁴ Department of Clinical Physiology, Nuclear Medicine & PET and Cluster for Molecular Imaging, Department of Biomedical Sciences, Rigshospitalet and University of Copenhagen, Blegdamsvej 9, 2100, Copenhagen, Denmark. akjaer@sund.ku.dk.

Abstract

Background: CD4⁺ T cells are central inflammatory mediators in the pathogenesis of autoimmune rheumatoid arthritis (RA), as they are one of the dominating cell types in synovial inflammation. Molecular imaging of CD4⁺ T cells has potential role for early detection and monitoring of RA. Here, we developed a new radiotracer for in vivo immunoPET imaging of murine CD4⁺ T cells and tested it in the collagen-induced arthritis (CIA) mouse model of human RA.

Results: The tracer, [⁶⁴Cu]Cu-NOTA-CD4-F(ab)'2 ([⁶⁴Cu]Cu-NOTA-CD4), was generated from F(ab)'2 fragments of R-anti-mouse CD4 antibodies conjugated to the 2-S-(isothiocyanatbenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (p-SCN-Bn-NOTA) chelator and radiolabeled with copper-64. Accumulation of the tracer and isotype control was evaluated in the CIA model and mice receiving whole-body irradiation (WBI) (5 Gy). The potential of [⁶⁴Cu]Cu-NOTA-CD4 for response assessment was evaluated in CIA induced mice treated with dexamethasone (DXM). Imaging data were compared with flow cytometry and immunohistochemistry (IHC) of inflammatory cells including CD4⁺ T cells. [⁶⁴Cu]Cu-NOTA-CD4 showed increased accumulation in T cell-rich tissues compared with isotype control (p < 0.0001). In addition, reduced accumulation of [⁶⁴Cu]Cu-NOTA-CD4 was observed in T cell-depleted tissue (p < 0.0001). Flow cytometry and IHC confirmed the increased infiltration of CD4⁺ T cells in CIA mice.

Conclusions: We developed and evaluated a new radiotracer, [⁶⁴Cu]Cu-NOTA-CD4, for immunoPET imaging of murine CD4⁺ T cells. [⁶⁴Cu]Cu-NOTA-CD4 was successfully synthesized by F(ab)'2 fragments of R-anti-mouse CD4 antibodies conjugated to a chelator and radiolabeled with copper-64. We found that our novel CD4 PET tracer can be used for noninvasive visualization of murine CD4⁺ T cells.

Keywords: Animal model; CD4+ T cells; Collagen-induced arthritis; Positron emission tomography (PET); Rheumatoid arthritis; [64Cu]Cu-NOTA-CD4.