Ardipradja Katie, Yeoh Shinn Dee, Alt Karen, O'Keefe Graeme, Rigopoulos Angela, Howells David W, Scott Andrew M, Peter Karlheinz, Ackerman Uwe, Hagemeyer Christoph E
Vascular Biotechnology Laboratory, Baker IDI, Melbourne, Australia; Atherothrombosis and Vascular Biology Laboratory, Baker IDI, Melbourne, Australia; Departments of Nuclear Medicine and Centre for PET, Austin Hospital, Melbourne, Australia; Department of Medicine, Dentistry and Health Sciences, The University of Melbourne, Melbourne, Australia.
Departments of Nuclear Medicine and Centre for PET, Austin Hospital, Melbourne, Australia.
Nucl Med Biol. 2014 Mar;41(3):229-37. doi: 10.1016/j.nucmedbio.2013.12.006. Epub 2013 Dec 18.
Activated platelets are key players in thrombosis and inflammation. We previously generated single-chain antibodies (scFv) against ligand-induced binding sites (LIBS) on the highly abundant platelet glycoprotein integrin receptor IIb/IIIa. The aim of this study was the construction and characterisation of a novel (18)F PET radiotracer based on this antibody.
ScFv(anti-LIBS) and control antibody mut-scFv were reacted with N-succinimidyl-4-[(18)F]fluorobenzoate (S[(18)F]FB). Radiolabeled scFv was incubated with in vitro formed platelet clots and injected into mice with FeCl(3) induced thrombus in the left carotid artery. Clots were imaged in the PET scanner and amount of radioactivity measured using an ionization chamber and image analysis. Assessment of vessel injury as well as the biodistribution of the radiolabeled scFv was studied.
After incubation with increasing concentrations of (18)F-scFv(anti-LIBS) clots had retained significantly higher amounts of radioactivity compared to clots incubated with radiolabeled (18)F-mut-scFv (13.3 ± 3.8 vs. 3.6 ± 1 KBq, p < 0.05, n = 9, decay corrected). In the in vivo experiments we found an high uptake of the tracer in the injured vessel compared with the non-injured vessel, with 12.6 ± 4.7% injected dose per gram (ID/g) uptake in the injured vessel and 3.7 ± 0.9% ID/g in the non-injured vessel 5 minutes after injection (p < 0.05, n = 6).
Our results show that the novel antibody radiotracer (18)F-scFv(anti-LIBS) is useful for the sensitive detection of activated platelets and thrombosis.
We describe the first (18)F variant of a scFv(anti-LIBS) against activated platelets. This diagnostic agent could provide a powerful tool for the assessment of acute thrombosis and inflammation in patients in the future.
活化血小板是血栓形成和炎症反应的关键因素。我们之前制备了针对高度丰富的血小板糖蛋白整合素受体IIb/IIIa上配体诱导结合位点（LIBS）的单链抗体（scFv）。本研究的目的是基于该抗体构建并表征一种新型的（18）F PET放射性示踪剂。
将scFv（抗LIBS）和对照抗体mut-scFv与N-琥珀酰亚胺基-4-[(18)F]氟苯甲酸酯（S[(18)F]FB）反应。将放射性标记的scFv与体外形成的血小板凝块孵育，并注射到左颈动脉有FeCl(3)诱导血栓的小鼠体内。在PET扫描仪中对凝块进行成像，并使用电离室和图像分析测量放射性量。研究了血管损伤评估以及放射性标记的scFv的生物分布。
与用放射性标记的（18）F-mut-scFv孵育的凝块相比，用浓度递增的（18）F-scFv（抗LIBS）孵育后，凝块保留的放射性量显著更高（13.3±3.8对3.6±1 KBq，p<0.05，n = 9，衰变校正）。在体内实验中，我们发现与未受伤血管相比，示踪剂在受伤血管中的摄取量很高，注射后5分钟，受伤血管中的摄取量为每克注射剂量的12.6±4.7%（ID/g），未受伤血管中的摄取量为3.7±0.9% ID/g（p<0.05，n = 6）。
我们的结果表明，新型抗体放射性示踪剂（18）F-scFv（抗LIBS）可用于敏感检测活化血小板和血栓形成。
我们描述了针对活化血小板的scFv（抗LIBS）的首个（18）F变体。这种诊断剂未来可能为评估患者急性血栓形成和炎症提供有力工具。
