We sought to assess the in vivo importance of scavenger receptor (SR)–mediated uptake of oxidized low-density lipoprotein (OxLDL) in atherogenesis and to test the efficacy of human antibody IK17-Fab or IK17 single-chain Fv fragment (IK17-scFv), which lacks immunologic properties of intact antibodies other than the ability to inhibit uptake of OxLDL by macrophages, to inhibit atherosclerosis.

The unregulated uptake of OxLDL by macrophage SR contributes to foam cell formation, but the importance of this pathway in vivo is uncertain.

Cholesterol-fed low-density lipoprotein receptor knockout (LDLR^−/−) mice were treated with intraperitoneal infusion of human IK17-Fab (2.5 mg/kg) 3 times per week for 14 weeks. Because anti-human antibodies developed in these mice, LDLR^−/−/low-density lipoprotein receptor Rag 1 double-knockout mice (lacking the ability to make immunoglobulins due to loss of T- and B-cell function) were treated with an adenoviral vector encoding adenovirus expressed (Adv)–IK17-scFv or control adenovirus-enhanced green fluorescent protein vector intravenously every 2 weeks for 16 weeks.

In LDLR^−/− mice, infusion of IK17-Fab was able to sustain IK17 plasma levels for the first 8 weeks, but these diminished afterward due to increasing murine anti-IK17 antibody titers. Despite this, after 14 weeks, a 29% decrease in en face atherosclerosis was noted compared with phosphate-buffered saline–treated mice. In LDLR^−/−/low-density lipoprotein receptor Rag 1 double-knockout mice, sustained levels of plasma IK17-scFv was achieved by Adv-IK17-scFv–mediated hepatic expression, which led to a 46% reduction (p < 0.001) in en face atherosclerosis compared with adenovirus-enhanced green fluorescent protein vector. Importantly, peritoneal macrophages isolated from Adv-IK17-scFv treated mice had decreased lipid accumulation compared with adenovirus-enhanced green fluorescent protein–treated mice.

These data support an important role for SR-mediated uptake of OxLDL in the pathogenesis of atherosclerosis and demonstrate that oxidation-specific antibodies reduce the progression of atherosclerosis, suggesting their potential in treating cardiovascular disease in humans.