Anti-fibrin monoclonal antibodies for radioimmunodetection: preliminary assessment in a rat model system

The D Dimer (DD) site formed by linkage of D domains from adjacent fibrin (FN) molecules is unique to cross-linked FN and its degradation products and is not found in FN monomer or fibrinogen (FB). Thus monoclonal antibodies (MAb) reactive to DD should have a very suitable specificity for in vivo thrombus detection. Two anti-DD MAbs have been labelled with 131-I and assessed as scintigraphic agents in a normal rat model system. Each rat received 3 sc implants of antigen covalently coupled to Sepharose beads: 1) Human DD 2) Human FB 3) Glycine (GL) (control). Scintigraphic images taken 7 days after injection of 131-I anti DD MAb showed clear localisation of both anti-DD MAbs to the DD implant rather than to the FB or GL implants with no localisation in normal tissues. This was confirmed in biodistribution studies. Injection of anti-DD MAbs DD-3B6/22 and DD-IC3/108 resulted in DD: blood ratios of 10.4 +/- 0.6 and 4.9 +/- 0.3 respectively. These results suggest that anti-DD MAbs will have potential for thrombus radioimmunodetection.