In-111 labeled monoclonal anti-(fibrin-specific) antibody: Detection of pulmonary emboli

The monoclonal antifibrin-64C5, radiolabeled with In-111 via diethylene triamine pentaacetyl-residues, may be used for in vivo detection of experimental pulmonary emboli. Although this antifibrin binds specifically to human fibrin even in the presence of fibrinogen, it crossreacted effectively with canine fibrin thus permitting the use of a canine model. Experimental thrombi were formed in an isolated segment of the jugular vein by mixing thrombin, canine blood and I-125 Fibrinogen. After 1 hr, the restraining ligatures wee removed to release the I-125 -thrombi which could be found in the lungs by imaging for I-125 activity. About 1 hr later, 1.5-2 mCi In-111 bound to 4-10 mg of 64C5 were injected intravenously and imaged for the next 24 hr. At the end of 24 hr, the animals were killed and the lungs imaged ex vivo for I-125 and In-111 activities. The excised lungs were examined by gross inspection, then sliced to ascertain the location of the emboli in the lungs. Tissue samples were obtained for scintillation counting. Control animals (n=3) were treated identically except they were injected with 4 mg In-111 labeled non-fibrin specific IgGl monoclonal antibody. Discrete in vivo localization was found in 4 of 6 animals injected with In-111 64C5 in areas of emboli. This was confirmed by gross visual inspection of the excised lungs. Control animals did not show localization in the areas of pulmonary emboli, even in the images of the excised lungs. Thus, these studies demonstrate the potential of monoclonal antibody-64C5 for the non-invasive localization and visualization of pulmonary emboli