SPECIFIC TARGETING OF INFECTIOUS FOCI WITH RADIOIODINATED HUMAN RECOMBINANT INTERLEUKIN-1 IN AN EXPERIMENTAL-MODEL

In the present study, radioiodinated human recombinant interleukin-1 ( IL-1) was investigated for its potential to image infectious foci in v ivo in an animal model of infection. Twenty-four hours after induction of a Staphylococcus aureus abscess in the left calf muscle, mice were i.v. injected with both iodine-125 labelled IL-1 and iodine-131 label led myoglobin, a size-matched control agent. The animals were killed f or tissue biodistribution studies at 2, 6, 12, 24 and 48 h p.i. Gamma camera images were obtained at 6, 24 and 48 h after injecting mice wit h I-123-IL-1. Radioiodinated IL-1 rapidly cleared from the body; after 12 h the abscess was the organ with the highest activity. The absolut e abscess uptake of I-125-IL-1 remained high compared to I-131-myoglob in, resulting in significantly higher abscess-to-muscle ratios of I-12 5-IL-1 compared to I-131-myoglobin. The ratios of I-125-IL-1 reached t he ultimate value of 44.4+/-10.8 at 48 h p.i., whereas the ratios of I -131-myoglobin did not exceed 5.9+/-0.7. Gamma camera imaging revealed clearly visible abscesses. In conclusion, our results demonstrate spe cific retention of radioiodinated IL-1 in the abscess, presumably by i nteraction of IL-1 with its receptor on the inflammatory cells. The hi gh target-to-background ratios that were obtained over the course of t ime indicate that the IL-1 receptor may be a valuable target for the i maging of infectious foci.