Monoclonal Autoantibody Against a Cryptic Epitope on Tissue-Adherent Low-Density Lipoprotein for Molecular Imaging in Atherosclerosis

BACKGROUND Antibody-based constructs for molecular imaging and therapeutic delivery provide promising opportunities for the diagnosis and treatment of atherosclerosis. OBJECTIVES The authors aimed to generate and characterize immunoglobulin (Ig)G monoclonal autoantibodies in atherosclerosis for targeting of novel molecular determinants. METHODS The authors created hybridomas from an unimmunized low-density lipoprotein (LDL) receptor-deficient (Ldlr(-/-)) mouse and selected an IgG2b isotype autoantibody, LO9, for further characterization. RESULTS LO9 reacted well with native LDL bound to immobilized matrix components and less well to oxidized LDL. LO9 binding to immobilized native LDL was not neutralized by fluid-phase native LDL, indicating an adhesion-dependent epitope. The authors localized the epitope to a 20 amino-acid peptide sequence (P5) in the globular amino-terminus of apolipoprotein B. LO9 reacted with antigen in mouse atherosclerosis and in both human stable and ruptured coronary atherosclerosis. Furthermore, in vivo near-infrared fluorescence molecular tomographic imaging, and ex vivo confocal microscopy showed that intravenously injected LO9 localized beneath endothelium of the aortic arch in Ldlr(-/-) mice, in the vicinity of macrophages. CONCLUSIONS The authors believe LO9 is the first example of an IgG autoantibody that reacts with a native LDL epitope revealed by adherence to tissue matrix. Antibodies against adherent native LDL have potential as molecular targeting agents for imaging of and therapeutic delivery to atherosclerosis. (c) 2022 The Authors. Published by Elsevier on behalf of the American College of Cardiology Foundation.

Automated summary

This study generated and characterized a novel autoantibody, LO9, in atherosclerosis for targeting of molecular determinants. LO9 reacted well with native LDL bound to immobilized matrix components and localized to a specific peptide sequence. LO9 showed reactivity with antigen in mouse and human atherosclerosis and localized beneath the endothelium in vivo.