Background: Interleukin (IL)-8 is a chemotactic cytokine that binds with high affinity to receptors on neutrophils. Previously we showed that 99mTc-labeled IL-8 is highly suitable for scintigraphic imaging in rabbit models of IM infection and of colitis.
Study design:99mTc-labeled IL-8 was tested for its potential to image pulmonary infection in three experimental rabbit models: aspergillosis in immunocompromised rabbits, pneumococcal (Gram-positive) pneumonia, and Escherichia coli-induced (Gram-negative) pneumonia in immunocompetent rabbits (four rabbits in each group). A derivative of hydrazinonicotinamide was used as bifunctional coupling agent to label IL-8 with 99mTc. Biodistribution of 99mTc IL-8 was determined both by gamma-camera imaging and by counting dissected tissues at 6 h after injection.
Results:99mTc IL-8 enabled early (within 2 h after injection) and excellent visualization of localization and extent of pulmonary infection in each of the three experimental models of pulmonary infection. Uptake of 99mTc IL-8 in the infected lung and the contralateral lung was (in percentage of the injected dose per gram of tissue ± SEM) at 6 h after injection 0.63 ± 0.12 and 0.12 ± 0.02 (aspergillosis), 0.89 ± 0.04 and 0.44 ± 0.04 (pneumococcal pneumonia), and 1.53 ± 0.12 and 0.36 ± 0.06 (E coli pneumonia), respectively. In the E coli model, uptake of 99mTc IL-8 in the focus of infection even exceeded uptake in the kidneys, the main clearing organs.
Conclusion:99mTc IL-8 offers many advantages over the conventionally used radiopharmaceuticals to image pulmonary infection, 67Ga citrate and radiolabeled leukocytes, ie, rapid and easy preparation, short time span between injection and imaging, low radiation burden and, most importantly, clear delineation of the infectious foci.