title: Development of a universal anti-polyethylene glycol reporter gene for noninvasive imaging of PEGylated probes.
abstract: A reporter gene can provide important information regarding the specificity and efficacy of gene or cell therapies. Although reporter genes are increasingly used in experimental and clinical studies, a highly specific yet nonimmunogenic reporter that can track genes and cells in vivo by multiple imaging technologies still awaits development. In this study, we constructed a versatile and nonimmunogenic reporter gene to noninvasively image gene expression or cell delivery by optical imaging, MRI, and small-animal PET.
  
  
  METHODS
  We cloned and expressed a membrane-anchored anti-polyethylene glycol (PEG) reporter that consists of the Fab fragment of a mouse anti-PEG monoclonal antibody, AGP3, fused to the C-like extracellular-transmembrane-cytosolic domains of the mouse B7-1 receptor. Binding of PEGylated probes (PEG-NIR797 for optical imaging, PEG-superparamagnetic iron oxide for MRI, and (124)I-PEG for small-animal PET) were examined in vitro and in vivo. In addition, we compared the specificity, immunogenicity, and probe toxicity of the anti-PEG reporter with the gold standard reporter gene, type 1 herpes simplex virus thymidine kinase (HSV-tk). Finally, we derived a humanized anti-PEG reporter and evaluated its imaging function in vivo with subcutaneous and metastatic tumor models in mice.
  
  
  RESULTS
  The cells or tumors that stably expressed anti-PEG reporters selectively accumulated various PEGylated imaging probes and could be detected by optical imaging, MRI, and small-animal PET. Importantly, the anti-PEG reporter displayed an imaging specificity comparable to the HSV-tk reporter but did not provoke immune responses or cause toxicity to the host. Furthermore, the humanized anti-PEG reporter retained high imaging specificity in vivo.
  
  
  CONCLUSIONS
  The highly specific and nonimmunogenic anti-PEG reporter may be paired with PEGylated probes to provide a valuable system to image gene expression or cell delivery in experimental and clinical studies.
authors.affiliation: Graduate Institute of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Kuo-Hsiang
authors.initials: KH
authors.lastname: Chuang
authors.forename: Hsin-Ell
authors.initials: HE
authors.lastname: Wang
authors.forename: Ta-Chun
authors.initials: TC
authors.lastname: Cheng
authors.forename: Shey-Cherng
authors.initials: SC
authors.lastname: Tzou
authors.forename: Wei-Lung
authors.initials: WL
authors.lastname: Tseng
authors.forename: Wen-Chun
authors.initials: WC
authors.lastname: Hung
authors.forename: Ming-Hong
authors.initials: MH
authors.lastname: Tai
authors.forename: Tien-Kuei
authors.initials: TK
authors.lastname: Chang
authors.forename: Steve R
authors.initials: SR
authors.lastname: Roffler
authors.forename: Tian-Lu
authors.initials: TL
authors.lastname: Cheng
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000235:genetics* / Q000276:immunology* / Q000633:toxicity; D003001:Cloning, Molecular; D005260:Female; D018014:Gene Transfer Techniques; D017930:Genes, Reporter; D006367:HeLa Cells; D018259:Herpesvirus 1, Human / Q000201:enzymology; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000235:genetics / Q000276:immunology / Q000633:toxicity; D008279:Magnetic Resonance Imaging; D051379:Mice; D057054:Molecular Imaging / Q000379:methods*; D015335:Molecular Probes / Q000235:genetics* / Q000276:immunology* / Q000633:toxicity; D041681:NIH 3T3 Cells; D009369:Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism; D055620:Optical Phenomena; D011092:Polyethylene Glycols / Q000378:metabolism*; D049268:Positron-Emission Tomography; D013937:Thymidine Kinase / Q000235:genetics
chemical_list: D000911:Antibodies, Monoclonal; D007140:Immunoglobulin Fab Fragments; D015335:Molecular Probes; D011092:Polyethylene Glycols; D013937:Thymidine Kinase