The kinetics of radiolabelled interleukin-8 in infection and sterile inflammation.

Radiolabelled interleukin-8 (IL-8) is a promising agent for the imaging of infection and inflammation. Several experiments were performed to explore further the imaging potential of radiolabelled IL-8. IL-8 was radioiodinated via the Bolton-Hunter method. Rabbits with focal infection (Escherichia coli, Staphylococcus aureus) or sterile inflammation (zymosan) were injected intravenously with 18.5 MBq (0.5 mCi) of 123I-IL-8. In separate studies, rabbits were injected intravenously with 111In-granulocytes with or without 125I-IL-8. Gamma camera images were obtained at 5 min, 1, 4 and 8 h post-injection (p.i.). Biodistribution was determined at 8 h p.i. In all models, the biodistribution of 123I-IL-8 was characterized by rapid blood clearance and high uptake in infection and sterile inflammation. All foci could be clearly visualized within 4 h p.i. Ex vivo abscess-to-contralateral muscle ratios increased to 114.7+/-23.0 (E. coli), 52.3+/-24.5 (S. aureus) and 49.8+/-8.3 (zymosan) at 8 h p.i. In the circulation, most 123I-IL-8 was bound to erythrocytes. The abscess uptake of 125I-IL-8 reached high levels despite reduced migration of granulocytes towards the site of infection due to the anti-inflammatory activity of intravenously injected IL-8. IL-8 could be injected without induction of neutropenia at a dosage of 2 ng kg(-1). In conclusion, the characteristics of radiolabelled IL-8 for imaging of infection and sterile inflammation are highly encouraging and warrant further optimization for clinical application.