Comparison of three different methods for radiolabelling human activated T lymphocytes

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Abstract
One approach in the treatment of ovarian cancer MOv18/anti-CD3 (biMAb OC/TR), which recognizes a 38-kDa glycoprotein expressed on ovarian carcinomas and the CD3 T cell receptor. However, little is known about the in vivo biodistribution of injected activated lymphocytes, information that could be obtained by scintigraphic imaging of radiolabelled T cells in order to visualize the migratory pattern. We compared the efficiency, stability and toxicity of technetium-99m hexamethylpropylene amine oxime (HMPAO),indium-111 oxine and fluorine-18 2-fluoro-2-deoxy-d-glucose (FDG) in radiolabelling activated lymphocytes targeted with biMAb OC/TR. The mean labelling efficiencies of111In-oxine and18F-FDG using 2.5×108 lymphocytes (68% and 64%, respectively) were more than twice that of99mTc-HMPAO (31%). Retention of the radionuclide in the cell was highest in the case of111In-oxine labelling (less than 25% of the initial cell-bound activity released after 240 min, as compared with 44% of the99mTc label in the same period and 45% of18F radionuclide released after 150 min). None of the three radiolabelling reagents induced any significant alteration in cell viability or immunophenotype. However, both111In-oxine and18F-FDG induced a loss of cytotoxic activity of lymphocytes against the ovarian carcinoma cell line IGROV1, and all three radiolabelling reagents caused a significant reduction in the proliferative ability of labelled lymphocytes compared to controls, with cell death occurring after 8–9 days. Radiolabelling with the more stable111In-oxine reagent using a higher number of lymphocytes (1.4x109) but the same total activity (around 55.5 MBq) resulted in improved labelled T cell viability and proliferative ability, although the mean labelling efficiency decreased (35.8%). Together the data suggest that111In-oxine at low activity per cell is the most appropriate reagent for radiolabelling activated retargeted T lymphocytes useful for in vivo biodistribution studies.