Imaging Focal Sites of Bacterial Infection in Rats with Indium-111-Labeled Chemotactic Peptide Analogs

(P4), were synthesized and evaluated for in vitro bioactivity and receptor binding. The peptides were radiotabeled with 1111n by transchelation and their biodistribution determined in rats at 5, 30, 60 and 120 min after injection. Localization at sites of infection was determined by scintillation camera imaging in animals with deep-thigh infection due to Esch-erichia coil. Images were recorded from 5 min to 2 hr after injection. All peptides maintained biologic activity (ECho for 02- production by human PMN's: 3-150 riM) and the ability to bind to the oligopeptide chemoattractant receptor on human PMN's (ECs0 for binding: 7.5-50 nM); biologic activity and receptor binding were highly correlated (r = 0.99). For all the peptides, blood clearance was rapid (half-lives: 21.5, 33.1, 31.6, and 28.7 min for P1, P2, P3, and P4, respectively). Biodistributions of the individual peptide