In vivo distribution of single chain variable fragment (scFv) against atherothrombotic oxidized LDL/β2-glycoprotein I complexes into atherosclerotic plaques of WHHL rabbits: Implication for clinical PET imaging

Background: Oxidized LDL (oxLDL) can exist as a complex with beta(2)-glycoprotein I (beta(2)GPI) in plasma/serum of patients with non-autoimmune atherosclerotic disease or antiphospholipid syndrome (APS). Nonetheless, direct in vivo evidence supporting the pathophysiological involvement of oxLDL/beta(2)GPI complexes and specific autoantibody against the complexes in developing atherothrombosis has yet been established. In the present study, we demonstrated in vivo distribution of single chain variable fragment of IgG anti-oxLDL/beta(2)GPI complexes (3H3-scFv) in Watanabe heritable hyperlipidemic (WHHL) rabbits by PET/CT imaging. Methods: An antibody-based PET probe, Cu-64-3H3-scFv, was established, and WHHL rabbits were applied for a non-autoimmune atherosclerotic model to demonstrate in vivo distribution of the probe. Results: 3H3-scFv has exhibits specificity towards beta(2)GPI complexed with oxLDL but neither a free form of beta(2)GPI nor oxLDL alone. Post-intravenous administration of Cu-64-3H3-scFv into WHHL rabbits has demonstrated a noninvasive approach for in vivo visualization of atherosderotic lesion. The imaging probe achieved ideal blood clearance and distribution for optimal imaging capacity in 24 h, significantly shorter than that of an intact IgG-based imaging probe. Cu-64-3H3-scFv targeted on atherosclerotic plaques in aortas of WHHL rabbits where extensive accumulation of lipid deposits was observed by lipid staining and autoradiography. The accumulation of Cu-64-3H3scFv in aortic segments of WHHL rabbits was 2.8-folds higher than that of controls (p = 0.0045). Conclusions: The present in vivo evidence supports the pathophysiological involvement of oxLDL/beta(2)GPI complexes in atherosclerotic complications of WHHL rabbits. Cu-64-3H3-scFv represents a novel PET imaging probe for non-invasive pathophysiological assessment of oxLDL/beta(2)GPI complexes accumulated in atherosclerotic plaques. (C) 2016 Elsevier B.V. All rights reserved.