Radiolabeled interleukin-8: Specific scintigraphic detection of infection within a few hours

Several small receptor-binding agents have been tested for imaging of infec tion and inflammation, The potential of chemotactic peptides and of interle ukins is promising and superior to that of conventional agents. In this stu dy, we investigated the potential of interleukin-8 (IL-8) to image infectio n in rabbits. Methods: IL-8 was labeled with I-123 using the Bolton-Hunter method. Twenty-fours hours after induction of Escherichia coli abscesses in the left thigh muscle, rabbits were injected intravenously with 18.5 MBq I -123-IL-8. gamma Camera images were obtained at 5 min and at 1, 4, and 8 h after injection. Biodistribution was determined 8 h after injection. Result s:I-123-IL-8 rapidly cleared from the blood. Accumulation of I-123-IL-8 in the abscess was visible as early as 1 h after injection. The highest absces s uptake was obtained 4 h after injection (2.6 +/- 0.2 percentage injected dose [%ID]), whereas I-123-IL-8 rapidly cleared from all other tissues. Thi s resulted in increases in abscess-to-background ratios to 13.0 +/- 0.7 (8 h after injection), as determined by quantification of the images. In tissu e biodistribution (8 h after injection), the abscess uptake was 0.057 +/- 0 .011 %ID/g with abscess-to-contralateral muscle ratios of 114.7 +/- 23.0. T he radioiodination method clearly affected the in vivo biodistribution of I L-8 because IL-8 iodinated using the lodo-Gen method cleared significantly slower from the blood and most other organs, resulting in poor visualizatio n of the abscess. Conclusion: The superior characteristics of IL-8 radioiod inated using the Bolton-Hunter method--i.e., high abscess uptake and rapid background clearance within a few hours-make IL-8 a promising agent to imag e infection and inflammation.