title: Human complement receptor type 1-directed loading of tissue plasminogen activator on circulating erythrocytes for prophylactic fibrinolysis.
abstract: Plasminogen activators (PAs) are not used for thromboprophylaxis due to rapid clearance, bleeding, and extravascular toxicity. We describe a novel strategy that overcomes these limitations. We conjugated tissue-type PA (tPA) to a monoclonal antibody (mAb) against complement receptor type 1 (CR1) expressed primarily on human RBCs. Anti-CR1/tPA conjugate, but not control conjugate (mIgG/tPA), bound to human RBCs (1.2 x 10(3) tPA molecules/cell at saturation), endowing them with fibrinolytic activity. In vitro, RBC-bound anti-CR1/tPA caused 90% clot lysis versus 20% by naive RBCs. In vivo, more than 40% of anti-CR1/(125)I-tPA remained within the circulation ( approximately 90% bound to RBCs) 3 hours after injection in transgenic mice expressing human CR1 (TgN-hCR1) versus less than 10% in wild-type (WT) mice, without RBC damage; approximately 90% of mIgG/(125)I-tPA was cleared from the circulation within 30 minutes in both WT and TgN-hCR1 mice. Anti-CR1/tPA accelerated lysis of pulmonary emboli and prevented stable occlusive carotid arterial thrombi from forming after injection in TgN-hCR1 mice, but not in WT mice, whereas soluble tPA and mIgG/tPA were ineffective. Anti-CR1/tPA caused 20-fold less rebleeding in TgN-hCR1 mice than the same dose of tPA. CR1-directed immunotargeting of PAs to circulating RBCs provides a safe and practical means to deliver fibrinolytics for thromboprophylaxis in settings characterized by a high imminent risk of thrombosis.
authors.affiliation: Institute for Environmental Medicine, 1 John Morgan Bldg, University of Pennsylvania Medical Center, 3620 Hamilton Walk, Philadelphia, PA 19104-6068, USA.
authors.forename: Sergei
authors.initials: S
authors.lastname: Zaitsev
authors.forename: Kristina
authors.initials: K
authors.lastname: Danielyan
authors.forename: Juan-Carlos
authors.initials: JC
authors.lastname: Murciano
authors.forename: Kumkum
authors.initials: K
authors.lastname: Ganguly
authors.forename: Tatiana
authors.initials: T
authors.lastname: Krasik
authors.forename: Ronald P
authors.initials: RP
authors.lastname: Taylor
authors.forename: Steven
authors.initials: S
authors.lastname: Pincus
authors.forename: Steven
authors.initials: S
authors.lastname: Jones
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Cines
authors.forename: Vladimir R
authors.initials: VR
authors.lastname: Muzykantov
mesh_terms: D000818:Animals; D004912:Erythrocytes / Q000378:metabolism*; D005342:Fibrinolysis / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D011655:Pulmonary Embolism / Q000188:drug therapy / Q000517:prevention & control; D011951:Receptors, Complement / Q000378:metabolism*; D015912:Thrombolytic Therapy; D013927:Thrombosis / Q000517:prevention & control; D010959:Tissue Plasminogen Activator / Q000008:administration & dosage*
chemical_list: D011951:Receptors, Complement; D010959:Tissue Plasminogen Activator