TY - JOUR
T1 - N-(4-F-18-Fluorobenzoyl)Interleukin-2 for PET of Human-Activated T Lymphocytes
AU - Di Gialleonardo, Valentina
AU - Signore, Alberto
AU - Glaudemans, Andor W. J. M.
AU - Dierckx, Rudi A. J. O.
AU - De Vries, Erik F. J.
PY - 2012/5
Y1 - 2012/5
N2 - Interleukin-2 (IL2) binds with high affinity to the IL2 receptors overexpressed on activated T lymphocytes in various pathologic conditions. Radiolabeling of IL2 with a positron-emitting isotope could provide a tool for noninvasive PET of activated T cells in immune-mediated diseases. We report the labeling of IL2 with N-succinimidyl 4-F-18-fluorolbenzoate (F-18-SFB) for the synthesis of N-(4-F-18-fluorobenzoyl)interleukin-2 (F-18-FB-IL2) and the in vitro and in vivo evaluation of this novel radiopharmaceutical for the detection of IL2 receptor-positive cells by PET. Methods: F-18-SFB was efficiently prepared using a 3-step radiochemical pathway. Purified F-18-SFB was incubated with IL2 in borate buffer (pH 8.5) and ethanol at 50 degrees C for 10 min. F-18-FB-IL2 was purified by reversed-phase high-performance liquid chromatography. As in vitro quality controls, a biologic binding assay, sodium dodecyl sulfate polyacrylamide gel electrophoresis, mass spectrometry, and 3-chloroacetic acid precipitation stability tests were performed. Biodistribution studies were performed in BALB/c mice to evaluate the distribution of the tracer in healthy animals. PET experiments were performed in severe combined immunodeficiency disease mice inoculated with phytohemoagglutinin-activated human peripheral blood mononuclear cells (hPBMc). Whole-body images were acquired 30 min after injection of 5-15 MBq of F-18-FB-IL2. Results: F-18-SFB was produced with a 34%-38% radiochemical yield. The radiochemical purity after solid-phase extraction purification ranged from 93% to 96%. Conjugation of F-18-SFB to IL2 yielded F-18-FB-IL2 as the major product. The radiochemical yield of F-18-FB-IL2 after high-performance liquid chromatography purification was 25%-35% based on F-18-SFB. F-18-FB-IL2 was stable in plasma at 37 degrees C and capable of stimulating T cells to an extent similar to native IL2. A biodistribution study showed highest tracer uptake in the kidneys and bladder due to rapid renal clearance of the tracer. Small-animal PET images showed binding of F-18-FB-IL2 to activated hPBMc proportional to the number of injected cells. Conclusion: We report the successful labeling of IL2 with F-18 for PET of activated T lymphocytes. F-18-FB-IL2 is stable, is biologically active, and allows in vivo detection of activated T lymphocytes.
AB - Interleukin-2 (IL2) binds with high affinity to the IL2 receptors overexpressed on activated T lymphocytes in various pathologic conditions. Radiolabeling of IL2 with a positron-emitting isotope could provide a tool for noninvasive PET of activated T cells in immune-mediated diseases. We report the labeling of IL2 with N-succinimidyl 4-F-18-fluorolbenzoate (F-18-SFB) for the synthesis of N-(4-F-18-fluorobenzoyl)interleukin-2 (F-18-FB-IL2) and the in vitro and in vivo evaluation of this novel radiopharmaceutical for the detection of IL2 receptor-positive cells by PET. Methods: F-18-SFB was efficiently prepared using a 3-step radiochemical pathway. Purified F-18-SFB was incubated with IL2 in borate buffer (pH 8.5) and ethanol at 50 degrees C for 10 min. F-18-FB-IL2 was purified by reversed-phase high-performance liquid chromatography. As in vitro quality controls, a biologic binding assay, sodium dodecyl sulfate polyacrylamide gel electrophoresis, mass spectrometry, and 3-chloroacetic acid precipitation stability tests were performed. Biodistribution studies were performed in BALB/c mice to evaluate the distribution of the tracer in healthy animals. PET experiments were performed in severe combined immunodeficiency disease mice inoculated with phytohemoagglutinin-activated human peripheral blood mononuclear cells (hPBMc). Whole-body images were acquired 30 min after injection of 5-15 MBq of F-18-FB-IL2. Results: F-18-SFB was produced with a 34%-38% radiochemical yield. The radiochemical purity after solid-phase extraction purification ranged from 93% to 96%. Conjugation of F-18-SFB to IL2 yielded F-18-FB-IL2 as the major product. The radiochemical yield of F-18-FB-IL2 after high-performance liquid chromatography purification was 25%-35% based on F-18-SFB. F-18-FB-IL2 was stable in plasma at 37 degrees C and capable of stimulating T cells to an extent similar to native IL2. A biodistribution study showed highest tracer uptake in the kidneys and bladder due to rapid renal clearance of the tracer. Small-animal PET images showed binding of F-18-FB-IL2 to activated hPBMc proportional to the number of injected cells. Conclusion: We report the successful labeling of IL2 with F-18 for PET of activated T lymphocytes. F-18-FB-IL2 is stable, is biologically active, and allows in vivo detection of activated T lymphocytes.
KW - interleukin 2
KW - F-18-SFB
KW - labeling
KW - inflammation imaging
KW - T lymphocytes
KW - INFLAMMATORY-BOWEL-DISEASE
KW - RHEUMATOID-ARTHRITIS
KW - F-18-FDG PET
KW - ATHEROSCLEROTIC PLAQUES
KW - RECEPTOR ANTAGONIST
KW - EMISSION TOMOGRAPHY
KW - CROHNS-DISEASE
KW - SCINTIGRAPHY
KW - INTERLEUKIN-2
KW - TC-99M-INTERLEUKIN-2
U2 - 10.2967/jnumed.111.091306
DO - 10.2967/jnumed.111.091306
M3 - Article
VL - 53
SP - 679
EP - 686
JO - Journal of Nuclear Medicine
JF - Journal of Nuclear Medicine
SN - 0161-5505
IS - 5
ER -