Early Detection of Localized Immunity in Experimental Autoimmune Myocarditis Using [^99mTc]Fucoidan SPECT

The aim of the study was to evaluate the ability of technetium-99m-fucoidan ([^99mTc]fucoidan), a molecular imaging agent specific for selectins, in the assessment of early localized immunity in a rat model of experimental autoimmune myocarditis (EAM).

EAM was induced in Lewis rats and troponin T; brain natriuretic peptide (BNP) and anti-myosin antibodies were measured in plasma. Separately, [^99mTc]fucoidan single-photon emission computed tomography (SPECT)/x-ray computed tomography (CT) was performed in the very early phase of myocarditis at 10, 15, and 21 days after immunization. Then, hearts were collected and used for autoradiography, well counting, histology, and flow cytometry analysis.

The EAM acute phase is characterized by extensive myocardial necrosis, release of troponin and BNP, and pericardial effusion. [^99mTc]Fucoidan uptake was significantly increased in EAM compared with controls starting from D15. There was a close relationship between uptake of the tracer and myocardial content in CD45+, CD8+, CD11b+, and CD31+ cells.

[^99mTc]Fucoidan SPECT/CT accurately diagnosed the autoimmune attack in the early steps of EAM and could be used to monitor disease evolution and therapy efficiency.