Detection of activated platelets in a mouse model of carotid artery thrombosis with 18 F-labeled single-chain antibodies.
BACKGROUND
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.


METHODS
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.


RESULTS
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).


CONCLUSIONS
Our results show that the novel antibody radiotracer (18)F-scFv(anti-LIBS) is useful for the sensitive detection of activated platelets and thrombosis.


CONCLUSIONS
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.
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.
Katie
K
Ardipradja
Departments of Nuclear Medicine and Centre for PET, Austin Hospital, Melbourne, Australia.
Shinn Dee
SD
Yeoh
Vascular Biotechnology Laboratory, Baker IDI, Melbourne, Australia; Atherothrombosis and Vascular Biology Laboratory, Baker IDI, Melbourne, Australia.
Karen
K
Alt
Departments of Nuclear Medicine and Centre for PET, Austin Hospital, Melbourne, Australia.
Graeme
G
O'Keefe
Ludwig Institute for Cancer Research, Austin Hospital, Melbourne, Australia.
Angela
A
Rigopoulos
The Florey Institute of Neuroscience and Mental Health, Austin Hospital, Melbourne, Australia.
David W
DW
Howells
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; Ludwig Institute for Cancer Research, Austin Hospital, Melbourne, Australia.
Andrew M
AM
Scott
Atherothrombosis and Vascular Biology Laboratory, Baker IDI, Melbourne, Australia; Central Clinical School, Monash University, Melbourne, Australia.
Karlheinz
K
Peter
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; Ludwig Institute for Cancer Research, Austin Hospital, Melbourne, Australia.
Uwe
U
Ackerman
Vascular Biotechnology Laboratory, Baker IDI, Melbourne, Australia; Central Clinical School, Monash University, Melbourne, Australia. Electronic address: christoph.hagemeyer@gmail.com.
Christoph E
CE
Hagemeyer
D000818:Animals; D001565:Benzoates / Q000737:chemistry; D001777:Blood Coagulation; D002341:Carotid Artery Thrombosis / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D004195:Disease Models, Animal; D005260:Female; D005462:Fluorine Radioisotopes; D007091:Image Processing, Computer-Assisted; D051379:Mice; D008810:Mice, Inbred C57BL; D015539:Platelet Activation; D049268:Positron-Emission Tomography; D057127:Single-Chain Antibodies / Q000737:chemistry / Q000493:pharmacokinetics
D001565:Benzoates; D005462:Fluorine Radioisotopes; D057127:Single-Chain Antibodies
Antibodies; PET/CT; Platelets; Thrombosis