Immunology and Cell Biology (1992) 70. 173-179
Evaluation of thrombus detection in a rabbit model using a technetium-99M-labelled anti-fibrin monoclonal antibody F-T. LEE\ L.J. MILNER^ G. R. BONIFACE', G. J. BAUTOVICH^ A. R. J. WEEDON^, P. G. BUNDESEN'', D. B. RYLATT'' and K. Z. WALKER^ ^ANSTO, Sydney; ^Centenary Institute of Cancer Medidne and Cell Biology, University of Sydney, Sydney; ^Department of Nuclear Medicine, Royal Prince Alfred Hospital, Sydney', New South Wales; and "^ACEN BiomedicalLimited, Brisbane, Queensland, Australia Summary Technetium-99 m (''''"'Tc)-Iabelled conjugates of an anti-fibrin monoclonal antibody, DD-3B6/22, have been assessed for their detection of vascular thrombi in a rabbit model. DD-3B6/22 bitids to a D-dimer epitope present on cross-linked fibrin but absent trom the fibrin monomer or fibrinogen. Injection of a '^'''"Tc-label led Fab' fragment of DD-3H6/22 allowed delineation of model thrombi as early as 30 min postinjection (p.i.) with optimal localization at 4-5 h. Thrombus label uptake at 4 h p.i. was 0.304 ± 0.106% injected dose/g {% ID/g) compared with 0.022 + 0.001% ID/g after the injection of a control Fab' fragment. These results suggest that the '*''"'Tc-label led Fab' fragment of DD-3B6/22 has excellent potential for scintigraphic detection of vascular thrombi in humans.
Introduction In recent years, several anti-fibrin monoclonal antibodies (mAb) have been radiolabeiled for the scintigraphic detection of vascular thrombi in both animals and humans'". The mAb I)D-3B6/22 is a murinc IgG3 antibody that reacts with high affinity to D-dimer (DD), a site unique to cross-linked fibrin (XL-FN).-^ This antibody has already been used extensively in assays to detect DD and its breakdown products in patient sera.'*'^ Iodine-131 ['"l]-labelled DD-3B6/22 has also been shown to localize specifically to DD-coupled Sepharose implanted subcutaneously in rats.^ More recently, a rabbit model has been described for the evaluation of DD-3B6/22 H , ^L J 1 L 1-.l^ conjugates. In this model, human UU coupled to Sepharose beads is seeded into a thrombus formed in the jugular vein, a strategy undertaken to circumvent the non-reactivity of the DD-3B6/22 antibody with clots
formed from rabbit blood. Gamma camera scintigraphy showed that [''^'!]-labelled intact and F(ab')2 fragments of DD-3B6/22 localized well to these model thrombi, although the F(ab')2 fragments allowed much earlier scintigraphic detection of the thrombus.*^ While these studies have established the specificity of DD-3B6/22 localization to intravascularly sited antigen, Technetium-99 m ('^'^"'Tc) would be a preferable radionuclide for clinical studies.*^ Recently, techniques have ^^t-en developed for labelling Fab' fragments of DD-3B6/22 with "'Tc,'
Evaluation of thrombus detection in a rabbit model using a technetium-99M-labelled anti-fibrin monoclonal antibody F-T. LEE\ L.J. MILNER^ G. R. BONIFACE', G. J. BAUTOVICH^ A. R. J. WEEDON^, P. G. BUNDESEN'', D. B. RYLATT'' and K. Z. WALKER^ ^ANSTO, Sydney; ^Centenary Institute of Cancer Medidne and Cell Biology, University of Sydney, Sydney; ^Department of Nuclear Medicine, Royal Prince Alfred Hospital, Sydney', New South Wales; and "^ACEN BiomedicalLimited, Brisbane, Queensland, Australia Summary Technetium-99 m (''''"'Tc)-Iabelled conjugates of an anti-fibrin monoclonal antibody, DD-3B6/22, have been assessed for their detection of vascular thrombi in a rabbit model. DD-3B6/22 bitids to a D-dimer epitope present on cross-linked fibrin but absent trom the fibrin monomer or fibrinogen. Injection of a '^'''"Tc-label led Fab' fragment of DD-3H6/22 allowed delineation of model thrombi as early as 30 min postinjection (p.i.) with optimal localization at 4-5 h. Thrombus label uptake at 4 h p.i. was 0.304 ± 0.106% injected dose/g {% ID/g) compared with 0.022 + 0.001% ID/g after the injection of a control Fab' fragment. These results suggest that the '*''"'Tc-label led Fab' fragment of DD-3B6/22 has excellent potential for scintigraphic detection of vascular thrombi in humans.
Introduction In recent years, several anti-fibrin monoclonal antibodies (mAb) have been radiolabeiled for the scintigraphic detection of vascular thrombi in both animals and humans'". The mAb I)D-3B6/22 is a murinc IgG3 antibody that reacts with high affinity to D-dimer (DD), a site unique to cross-linked fibrin (XL-FN).-^ This antibody has already been used extensively in assays to detect DD and its breakdown products in patient sera.'*'^ Iodine-131 ['"l]-labelled DD-3B6/22 has also been shown to localize specifically to DD-coupled Sepharose implanted subcutaneously in rats.^ More recently, a rabbit model has been described for the evaluation of DD-3B6/22 H , ^L J 1 L 1-.l^ conjugates. In this model, human UU coupled to Sepharose beads is seeded into a thrombus formed in the jugular vein, a strategy undertaken to circumvent the non-reactivity of the DD-3B6/22 antibody with clots
formed from rabbit blood. Gamma camera scintigraphy showed that [''^'!]-labelled intact and F(ab')2 fragments of DD-3B6/22 localized well to these model thrombi, although the F(ab')2 fragments allowed much earlier scintigraphic detection of the thrombus.*^ While these studies have established the specificity of DD-3B6/22 localization to intravascularly sited antigen, Technetium-99 m ('^'^"'Tc) would be a preferable radionuclide for clinical studies.*^ Recently, techniques have ^^t-en developed for labelling Fab' fragments of DD-3B6/22 with "'Tc,'
