Immuno-PET Imaging of Atherosclerotic Plaques with [⁸⁹Zr]Zr-Anti-CD40 mAb—Proof of Concept

Non-invasive imaging of atherosclerosis can help in the identification of vulnerable plaque lesions. CD40 is a co-stimulatory molecule present on various immune and non-immune cells in the plaques and is linked to inflammation and plaque instability. We hypothesize that a ⁸⁹Zr-labeled anti-CD40 monoclonal antibody (mAb) tracer has the potential to bind to cells present in atherosclerotic lesions and that CD40 Positron Emission Tomography (PET) can contribute to the detection of vulnerable atherosclerotic plaque lesions. To study this, wild-type (WT) and ApoE^−/− mice were fed a high cholesterol diet for 14 weeks to develop atherosclerosis. Mice were injected with [⁸⁹Zr]Zr-anti-CD40 mAb and the aortic uptake was evaluated and quantified using PET/Computed Tomography (CT) imaging. Ex vivo biodistribution was performed post-PET imaging and the uptake in the aorta was assessed with autoradiography and compared with Oil red O staining to determine the tracer potential to detect atherosclerotic plaques. On day 3 and 7 post injection, analysis of [⁸⁹Zr]Zr-anti-CD40 mAb PET/CT scans showed a more pronounced aortic signal in ApoE^−/− compared to WT mice with an increased aorta-to-blood uptake ratio. Autoradiography revealed [⁸⁹Zr]Zr-anti-CD40 mAb uptake in atherosclerotic plaque areas in ApoE^−/− mice, while no signal was found in WT mice. Clear overlap was observed between plaque areas as identified by Oil red O staining and autoradiography signal of [⁸⁹Zr]Zr-anti-CD40 mAb in ApoE^−/− mice. In this proof of concept study, we showed that PET/CT with [⁸⁹Zr]Zr-anti-CD40 mAb can detect atherosclerotic plaques. As CD40 is associated with plaque vulnerability, [⁸⁹Zr]Zr-anti-CD40 mAb has the potential to become a tracer to detect vulnerable atherosclerotic plaques.