^99mTc-cAbVCAM1-5 Imaging Is a Sensitive and Reproducible Tool for the Detection of Inflamed Atherosclerotic Lesions in Mice

Abstract

99m Tc-cAbVCAM1-5, a single-domain antibody fragment directed against mouse or human vascular cell adhesion molecule 1 (VCAM-1), recently has been proposed as a new imaging agent for the detection of inflamed atherosclerotic lesions. Indeed, in a mouse model of atherosclerosis, 99m Tc-cAbVCAM1-5 specifically bound to VCAM-1-positive lesions, thereby allowing their identification on SPECT images. The purpose of the present study was to investigate 99m TccAbVCAM1-5 imaging sensitivity using a reference statin therapy. Methods: Thirty apolipoprotein E-deficient mice were fed a westerntype diet. First, the relationship between the level of VCAM-1 expression and 99m Tc-cAbVCAM1-5 uptake was evaluated in 18 mice using immunohistochemistry and autoradiography. Second, longitudinal SPECT/CT imaging was performed on control (n 5 9) or atorvastatintreated mice (0.01% w/w, n 5 9). Results: 99m Tc-cAbVCAM1-5 uptake in atherosclerotic lesions correlated with the level of VCAM-1 expression (P , 0.05). Atorvastatin exerted significant antiatherogenic effects, and 99m Tc-cAbVCAM1-5 lesion uptake was significantly reduced in 35-wk-old atorvastatin-treated mice, as indicated by ex vivo γ-well counting and autoradiography (P , 0.05). SPECT imaging quantification based on contrast-enhanced CT was reproducible (interexperimenter intraclass correlation coefficient, 0.97; intraexperimenter intraclass correlation coefficient, 0.90), and yielded results that were highly correlated with tracer biodistribution (r 5 0.83; P , 0.0001). Therefore, reduced 99m Tc-cAbVCAM1-5 uptake in atorvastatin-treated mice was successfully monitored noninvasively by SPECT/CT imaging (0.87 ± 0.06 vs. 1.11 ± 0.09 percentage injected dose per cubic centimeter in control group, P , 0.05). Conclusion: 99m TccAbVCAM1-5 imaging allowed the specific, sensitive, and reproducible quantification of VCAM-1 expression in mouse atherosclerotic lesions. 99m Tc-cAbVCAM1-5 therefore exhibits suitable characteristics for the evaluation of novel antiatherogenic agents.

Evaluation of Antiatherogenic Properties of Ezetimibe Using 3H-Labeled Low-Density-Lipoprotein Cholesterol and 99mTc-cAbVCAM1–5 SPECT in ApoE−/− Mice Fed the Paigen Diet

“…The benefits of the 50% reduction in Paigen diet-induced hypercholesterolemia were quantified in vivo using SPECT performed with 99m Tc-cAbV-CAM1-5. This radiolabeled single-domain antibody, which is currently undergoing clinical translation, targets the inflammatory marker VCAM-1 and has been validated as a sensitive and reproducible tool for imaging inflammation in mouse atherosclerotic lesions (14). In the present study, atherosclerotic lesions were readily observable in the aortic root and ascending aorta on SPECT images.…”

“…VCAM-1 intensity was graded as low (1), moderate (2), or strong (3) by 2 masked observers. 99m Tc cAbVCAM1-5 uptake in autoradiographic images was expressed either as a concentration (%ID/g) or as the total uptake per slice (%ID/slice), as previously described (14).…”

“…The effect of ezetimibe on LDL cholesterol metabolism and LDL-derived cholesterol fecal excretion was therefore evaluated with 3 H-cholesteryl oleate-labeled LDL kinetics, and its effect on inflammatory plaque development was evaluated using 99m Tc-cAbVCAM1-5 imaging in ApoE 2/2 mice fed the Paigen diet. 99m Tc-cAbVCAM1-5, currently under clinical translation, is a SPECT radiotracer directed against the inflammatory marker vascular cell adhesion molecule 1 (VCAM-1) (13,14). This molecular imaging agent belongs to a new class of radiotracer derived from single-domain antibodies, or variable domain of the heavy chain of the heavy-chain antibody, which are composed of the single variable domain of camelidae immunoglobulins.…”

“…This molecular imaging agent belongs to a new class of radiotracer derived from single-domain antibodies, or variable domain of the heavy chain of the heavy-chain antibody, which are composed of the single variable domain of camelidae immunoglobulins. Aortic atherosclerotic lesions have been successfully detected in ApoE 2/2 mice fed a western diet using 99m Tc-cAbVCAM1-5 imaging, and the sensitivity of this tool has been demonstrated using statin therapy as a gold standard (13,14). This molecular imaging agent can therefore be used for the preclinical noninvasive evaluation of antiatherosclerotic therapies.…”

A Nanobody‐Based Approach to Amyloid Diseases, the Gelsolin Case Study

“…Equipped with a radionuclide, they can be applied as imaging tracers in a single-photon emission computed tomography (SPECT) or positron emission tomography (PET)-based set-up allowing in vivo visualization of tumours, artherosclerotic plaques and rheumatoid arthritis-associated inflammation sites [36][37][38]. Nanobodies are also capable of stabilizing proteins in a particular conformation and of minimizing structural flexibility.…”