Engineered antibody fragments with infinite affinity as reporter genes for PET imaging

Liu H. Wei, Tove Olafsen, Caius Radu, Isabel J. Hildebrandt, Mark R. McCoy, Michael E. Phelps, Claude Meares, Anna M. Wu, Johannes Czernin, Wolfgang A. Weber

Research output: Contribution to journalArticle

37 Scopus citations

Abstract

Reporter gene imaging has great potential for many clinical applications including the tracking of transplanted cells and monitoring of gene therapy. However, currently available reporter gene-reporter probe combinations have significant limitations with the biodistribution of the reporter probe and the specificity and immunogenicity of the reporter gene. The objective of the present study was to evaluate a new approach for reporter gene imaging based on cell surface expression of antibody fragments that can irreversibly bind to radiometal chelates. Methods: We developed a new reporter gene, designated 1,4,7,10-tetraazacyclodocecane-N,N′,N″,N‴-tetraacetic acid (DOTA) antibody reporter 1 (DAbR1), which consists of the single-chain Fv (scFv) fragment of the anti-Y-DOTA antibody 2D12.5/G54C fused to the human T cell CD4 transmembrane domain. The corresponding reporter probe is yttrium-(S)-2-(4- acrylamidobenzyl)-DOTA (*Y-AABD), a DOTA complex that binds irreversibly to a cysteine residue in the 2D12.5/G54C antibody. U-87 glioma cells were stably transfected with a DAbR1 expression vector. Binding of *Y-AABD to transfected and wild-type cells was studied in vitro and in vivo. Results: Flow cytometry revealed high expression of the DAbR1 protein on the cell surface of tumor cells. Uptake of 90Y-AABD in DAbR1-expressing human U-87 glioma xenografts was 6.2 (±1.3) percentage injected dose per gram (%ID/g) at 1 h and 4.9 (±0.62) %ID/g at 24 h after injection. The corresponding tumor-to-plasma ratios were 45:1 and 428:1, respectively. Uptake by U-87 tumors without the DAbR1 gene was 0.16 (±0.02) %ID/g at 1 h and 0.05 (±0.03) %ID/g at 24 h. PET images in mice with 86Y-AABD demonstrated intense uptake in DAbR1-positive tumors and low background activity in the liver. Conclusion: These findings indicate that cell surface expression of radiometal chelate binding antibodies such as 2D12.5/G54C is a promising strategy for reporter gene imaging.

Original languageEnglish (US)
Pages (from-to)1828-1835
Number of pages8
JournalJournal of Nuclear Medicine
Volume49
Issue number11
DOIs
StatePublished - Nov 1 2008

Keywords

  • AABD
  • Noninvasive imaging
  • Reporter gene
  • Single-chain Fv antibody
  • Surface expression

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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    Wei, L. H., Olafsen, T., Radu, C., Hildebrandt, I. J., McCoy, M. R., Phelps, M. E., Meares, C., Wu, A. M., Czernin, J., & Weber, W. A. (2008). Engineered antibody fragments with infinite affinity as reporter genes for PET imaging. Journal of Nuclear Medicine, 49(11), 1828-1835. https://doi.org/10.2967/jnumed.108.054452