Receptor Binding Ligands to Image Infection

The current gold standard for imaging infection is radiolabeled white blood cells. For reasons of safety, simplicity and cost, it would be desirable to have a receptor-specific ligand that could be used for imaging infection and that would allow a differential diagnosis between sterile and septic inflammatory processes. Ligands tested for this purpose include labeled peptides (^99mTc-labeled f-Met-Leu-Phe, ¹²³I-IL-1ra, ^99mTc-IL-8, ^99mTc-P483H, ^99mTc-P1827DS, ^99mTc-C5ades- Arg, ^99mTc-RP517, 111In-DPC11870-11), human polyclonal antibodies, monoclonal antibodies, antibody fragments, antimicrobial agents (ciprofloxacin, sparfloxacin, ceftizoxime, isoniazid, ethambutol, fluconazole, all labeled with 9^99mTc), antimicrobial peptides and bacteriophages. Radiolabeled antibodies represent a valid alternative to labeled white blood cells under specific conditions and indications. Radiolabeled antibiotics and antimicrobial peptides are promising candidates for an infection-specific radiopharmaceutical. However, at present we still need to investigate many basic aspects to better understand the mechanisms of binding and accumulation of this class of radiopharmaceuticals to bacteria.