¹¹¹In-anti-F4/80-A3-1 antibody: a novel tracer to image macrophages

  • Eur J Nucl Med Mol Imaging. 2015 Aug;42(9):1430-8. doi: 10.1007/s00259-015-3084-8.
Samantha Y A Terry  1 ,  Otto C Boerman ,  Danny Gerrits ,  Gerben M Franssen ,  Josbert M Metselaar ,  Steffi Lehmann ,  Wim J G Oyen ,  Christian A Gerdes ,  Keelara Abiraj
Affiliations
  • 1. Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands, [email protected].
PMID: 26012900 DOI: 10.1007/s00259-015-3084-8
Abstract

Purpose: Here, the expression of F4/80 on the cell surface of murine Macrophages was exploited to develop a novel imaging tracer that could visualize Macrophages in vivo.

Methods: The immunoreactive fraction and IC50 of anti-F4/80-A3-1, conjugated with diethylenetriaminepentaacetic acid (DTPA) and radiolabelled with (111)In, were determined in vitro using murine bone marrow-derived Macrophages. In vivo biodistribution studies were performed with (111)In-anti-F4/80-A3-1 and isotype-matched control antibody (111)In-rat IgG2B at 24 and 72 h post-injection (p.i.) in SCID/Beige mice bearing orthotopic MDA-MB-231 xenografts. In some studies mice were also treated with liposomal clodronate. Macrophage content in tissues was determined immunohistochemically. Micro-single photon emission computed tomography (SPECT)/CT images were also acquired.

Results: In vitro binding assays showed that (111)In-anti-F4/80-A3-1 specifically binds F4/80 receptor-positive Macrophages. The immunoreactivity of anti-F4/80-A3-1 was 75 % and IC50 was 0.58 nM. In vivo, injection of 10 or 100 μg (111)In-anti-F4/80-A3-1 resulted in splenic uptake of 78 %ID/g and 31 %ID/g, respectively, and tumour uptake of 1.38 %ID/g and 4.08 %ID/g, respectively (72 h p.i.). Liposomal clodronate treatment reduced splenic uptake of 10 μg (111)In-anti-F4/80-A3-1 from 248 %ID/g to 114 %ID/g and reduced (111)In-anti-F4/80-A3-1 uptake in the liver and femur (24 h p.i.). Tracer retention in the blood and tumour uptake increased (24 h p.i.). Tumour uptake of (111)In-anti-F4/80-A3-1 was visualized by microSPECT/CT. Macrophage density in the spleen and liver decreased in mice treated with liposomal clodronate. Uptake of (111)In-rat IgG2B was lower in the spleen, liver and femur when compared to (111)In-anti-F4/80-A3-1.

Conclusion: Radiolabelled anti-F4/80-A3-1 antibodies specifically localize in tissues infiltrated by Macrophages in mice and can be used to visualize tumours. The liver and spleen act as antigen sink organs for macrophage-specific tracers.

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