(123)Iodine-labelled anti-VCAM-1 antibody scintigraphy in the assessment of experimental colitis

Objectives To evaluate the usefulness of I-123-labelled anti-vascular cell adhesion molecule-12 (VCAM-1) monoclonal antibody (MAb) scintigraphy in the assessment of colonic inflammatory damage. Design Colitis was induced by intracolonic administration of 30 mg trinitro benzenesulphonic acid in 0.5 mi of 50% (v/v) ethanol. Rats injected with ve hicle served as controls. Animals were studied at day 7 after induction of colitis. Methods Scintigraphy was performed in control and trinitrobenzenesulphonic acid-induced colitic rats 2, 4 and 24 h after intravenous administration of I-123-anti-VCAM-1 MAb, Scintigraphic uptake was quantified in selected are as on scintigraphs. Animals were killed, tissue I-123 radioactivity accumul ation was measured, and accumulation of anti-VCAM-1 MAb in each organ was c alculated. Tc-99m-hexamethyl propylene amine oxime-labelled leucocyte scint igraphy was performed in additional groups of animals for comparison. Results Colonic tracer uptake was visible in scans of colitic, but not cont rol animals. Quantification of scintigraphic uptake in the colon was signif icantly higher in colitic rats than in control animals (P < 0.0001). The sp ecificity of the increase was demonstrated by lack of I-123-labelled non-bi nding MAb uptake in the colon, and by displacement of I-123-anti-VCAM-1 MAb colonic uptake by pre-treatment with unlabelled MAb. Accumulation of anti- VCAM-1 MAb in the colon of colitic rats was eightfold higher than in contro l animals. Strong correlations were found between quantification of scintig raphic uptake, anti-VCAM-1 MAb accumulation, histological damage and myelop eroxidase activity in the colon. Conclusion I-123-labelled anti-VCAM-1 MAb scintigraphy allows an accurate e valuation of colonic inflammatory damage in trinitrobenzenesulphonic acid-i nduced colitis, suggesting a potential role for this imaging technique in t he assessment of human IBD. Eur J Gastroenterol Hepatol 13:31-38 (C) 2001 L ippincott Williams & Wilkins.