title: In vivo imaging of molecularly targeted phage.
abstract: Rapid identification of in vivo affinity ligands would have far-reaching applications for imaging specific molecular targets, in vivo systems imaging, and medical use. We have developed a high-throughput method for identifying and optimizing ligands to map and image biologic targets of interest in vivo. We directly labeled viable phage clones with far-red fluorochromes and comparatively imaged them in vivo by multichannel fluorescence ratio imaging. Using Secreted Protein Acidic and Rich in Cysteine (osteonectin) and vascular cell adhesion molecule-1 as model targets, we show that: 1) fluorescently labeled phage retains target specificity on labeling; 2) in vivo distribution can be quantitated (detection thresholds of approximately 300 phage/mm(3) tissue) throughout the entire depth of the tumor using fluorescent tomographic imaging; and 3) fluorescently labeled phage itself can serve as a replenishable molecular imaging agent. The described method should find widespread application in the rapid in vivo discovery and validation of affinity ligands and, importantly, in the use of fluorochrome-labeled phage clones as in vivo imaging agents.
authors.affiliation: Center for Molecular Imaging Research, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Kelly
authors.forename: Peter
authors.initials: P
authors.lastname: Waterman
authors.forename: Ralph
authors.initials: R
authors.lastname: Weissleder
mesh_terms: D000818:Animals; D001435:Bacteriophages / Q000737:chemistry* / Q000235:genetics; D018390:Gene Targeting / Q000379:methods*; D051379:Mice; D008819:Mice, Nude; D008856:Microscopy, Fluorescence; D015676:Osteonectin / Q000032:analysis / Q000235:genetics; D019010:Vascular Cell Adhesion Molecule-1 / Q000032:analysis / Q000235:genetics; D023041:Xenograft Model Antitumor Assays / Q000379:methods
chemical_list: D015676:Osteonectin; D019010:Vascular Cell Adhesion Molecule-1