Original article Anti-t-PA antibodies in acute myocardial infarction after thrombolysis with rt-PA Massimo Cugno a, ⁎, Roberto Castelli a , Giuliana Bisiani b , Samantha Griffini a , Pier Luigi Meroni c a Department of Internal Medicine, University of Milan, IRCCS Fondazione Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena, Via Pace 9, 20122, Milan, Italy b Department of Cardiology, Sesto San Giovanni Hospital, Viale G. Matteotti 83, 20099, Sesto San Giovanni, Milan, Italy c Department of Internal Medicine, University of Milan, Istituto Auxologico IRCCS, Via G. Spagnoletto 3, 20149, Milan, Italy abstract article info Article history: Received 4 September 2009 Received in revised form 17 September 2009 Accepted 21 September 2009 Keywords: Tissue-type plasminogen activator Acute myocardial infarction Antibodies Reocclusion Background: Thrombolysis with recombinant tissue-type plasminogen activator (rt-PA) is successfully used in acute myocardial infarction with ST elevation (STEMI). Reocclusions follow rt-PA treatment in up to 30% of patients within one year. The infusion of rt-PA may induce the production of anti-t-PA antibodies which could interfere with the function of the native t-PA molecule. Methods: In order to detect and characterise anti-t-PA antibodies, plasma samples were collected from 30 STEMI patients (20 treated and 10 not treated with rt-PA) at baseline before rt-PA infusion and then 15, 30, 90 and 180 days after STEMI and from 40 healthy subjects at baseline only. Immunoenzymatic, chromatographic and chromogenic methods were employed. Results: An increase of anti-t-PA antibodies was observed 15 days (IgM, p = 0.0001) and 30 days (IgG, p = 0.0001) after rt-PA infusion. Six patients had large increases of anti-t-PA IgG which bound the catalytic domain of t-PA (two cases) or kringle 2 domain (four cases), were of IgG1 or IgG3 subclasses and interacted with the t-PA molecule in fluid phase. Conclusion: The infusion of rt-PA may induce the production of specific antibodies that bind active sites of t-PA, thus potentially reducing its in vivo function. © 2009 European Federation of Internal Medicine. Published by Elsevier B.V. All rights reserved. 1. Introduction In acute myocardial infarction (AMI), treatment strategies aimed at rapidly restoring complete and persistent coronary flow, and recanalisation of the infarct-related artery is the target of both pharmacological and mechanical reperfusion techniques. The reperfusion regimens for patients with AMI and ST elevation (STEMI) are based on percutaneous intervention (percutaneous transluminal coronary angioplasty, PTCA) if this procedure can be promptly performed by skilled personnel, or on antithrombotic therapy with thrombolytic, antiplatelet and anticoagulant agents. The two reperfusion strategies have been compared in a number of randomised clinical trials, which have shown that mechanical reperfusion leads to better clinical outcomes [1,2]. The success of pharmacological reperfusion strictly depends on the time interval of its implementation after the event, and a recent randomised and controlled study by Fernandez-Aviles et al. has demonstrated that the two strategies are not mutually exclusive, with early post-fibrinolysis angioplasty being equivalent to primary angioplasty in limiting infarct size and preserving left ventricular function [3]. Recombinant tissue-type plasminogen activator (rt-PA) is a widely used thrombolytic drug because of its high fibrin specificity [4] and efficacy if administered early. It removes intravascular fibrin in vivo by converting plasminogen to plasmin, a proteolytic enzyme that degrades fibrin and restores blood flow through the infarct-related coronary artery, thus preserving ventricular function and improving survival. However, one major drawback of rt-PA treatment is coronary artery reocclusion, which occurs in 10% of patients before discharge and up to 30% in the first year [5]. Like other recombinant molecules that induce an immune response when administered to humans [6,7], rt-PA may trigger the production of antibodies against the infused molecule [8,9] because native and recombinant molecules have the same amino acid sequence but different glycosylation patterns. These antibodies may favour a thrombophilic situation by cross-reacting with the endoge- nous protein (t-PA) and reducing its activity, and by causing endothelial stress and intravascular inflammation as a result of antigen-antibody reactions leading to complement activation. They may also reduce the efficacy of the drug if its reinfusion is needed to treat a new AMI event. Finally, they may increase vascular permeability and vasodilation, thus giving rise to angioedema episodes [10,11] and anaphylactoid reactions [12,13]. The aim of this study was to measure anti-t-PA antibodies in serial blood samples taken from STEMI patients treated with rt-PA (alteplase), and characterise them biochemically and functionally. This was done by analysing the immunoglobulin subclasses, studying their interactions with the rt-PA molecule and its functional epitopes, and assessing their capacity to inhibit t-PA activity in vitro. European Journal of Internal Medicine 21 (2010) 25–29 ⁎ Corresponding author. Tel.: +39 02 55035340; fax: +39 02 50320742. E-mail address: massimo.cugno@unimi.it (M. Cugno). 0953-6205/$ – see front matter © 2009 European Federation of Internal Medicine. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.ejim.2009.09.011 Contents lists available at ScienceDirect European Journal of Internal Medicine journal homepage: www.elsevier.com/locate/ejim