title: Targeting of antibody-conjugated plasminogen activators to the pulmonary vasculature.
abstract: Thrombolytic therapy has not been widely used for pulmonary embolism due to less than optimal results with conventional plasminogen activators. We propose a new approach to deliver plasminogen activators to the luminal surface of the pulmonary vasculature to potentially improve dissolution of pulmonary thromboemboli. Our previous studies have documented that a monoclonal antibody (mAb) to angiotensin-converting enzyme (anti-angiotensin-converting enzyme mAb 9B9) accumulates in the lungs of various animal species after systemic administration. We coupled 125I-labeled biotinylated plasminogen activators (single-chain urokinase plasminogen activator, tissue-type plasminogen activator and streptokinase) to biotinylated mAb 9B9, using streptavidin as a cross-linker. The fibrinolytic activity of plasminogen activators was not changed significantly by either biotinylation or by coupling to streptavidin. Antibody-conjugated plasminogen activators bind to the antigen immobilized in plastic wells and provide lysis of fibrin clots formed in these wells. Therefore, antibody-conjugated plasminogen activators bound to their target antigen retain their capacity to activate plasminogen. One hour after i.v. injection of mAb 9B9-conjugated radiolabeled biotinylated single-chain urokinase plasminogen activator, biotinylated tissue-type plasminogen activator or biotinylated-streptokinase in rats, the level of radiolabel was 7.4 +/- 0.8, 5.9 +/- 0.4 and 3.6 +/- 0.4% of injected dose/g (ID/g) of lung tissue vs. 0.5 +/- 0.01, 0.3 +/- 0.01 and 0.6 +/- 0.3% ID/g after injection of the same activators conjugated with control mouse IgG (P < .01 in all cases). Injection of mAb 9B9-conjugated radiolabeled plasminogen activator led to its rapid pulmonary uptake with a peak value 6.2 +/- 1.2% ID/g attained 3 hr after injection. One day later, 2.2 +/- 0.5% of the injected radioactivity was found per gram of lung tissue, although the blood level was 0.13 +/- 0.03% ID/g (lung/blood ratio 16.7 +/- 0.3). Therefore, conjugation of plasminogen activators with anti-angiotensin-converting enzyme mAb 9B9 provides their specific targeting to and prolonged association with the pulmonary vasculature. These results provide a basis for study of the local pulmonary fibrinolysis by mAb 9B9-conjugated plasminogen activators.
authors.affiliation: Institute for Environmental Medicine, University of Pennsylvania, USA.
authors.forename: V R
authors.initials: VR
authors.lastname: Muzykantov
authors.forename: E S
authors.initials: ES
authors.lastname: Barnathan
authors.forename: E N
authors.initials: EN
authors.lastname: Atochina
authors.forename: A
authors.initials: A
authors.lastname: Kuo
authors.forename: S M
authors.initials: SM
authors.lastname: Danilov
authors.forename: A B
authors.initials: AB
authors.lastname: Fisher
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage*; D008168:Lung / Q000098:blood supply / Q000378:metabolism*; D051379:Mice; D010960:Plasminogen Activators / Q000008:administration & dosage*; D011655:Pulmonary Embolism / Q000628:therapy*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013300:Streptokinase / Q000008:administration & dosage; D015912:Thrombolytic Therapy; D014018:Tissue Distribution
chemical_list: D000911:Antibodies, Monoclonal; D013300:Streptokinase; D010960:Plasminogen Activators