Abstract 13218: Remodeling of High Density Lipoprotein Induced by CSL112: Structure and Function of the Remodeled Lipoproteins

Introduction: CSL112 is a novel formulation of human apolipoprotein A-I (apoA-I) suitable for intravenous infusion, currently in development for reducing the high rate of early recurrent events after acute myocardial infarction. Infusion of CSL112 into healthy volunteers causes HDL remodeling, with an immediate rise in lipid-poor apoA-I and a strong and immediate increase in the ABCA1-dependent cholesterol efflux capacity of plasma. Interaction of CSL112 with whole plasma or purified HDL gives rise to three new remodeled HDL species: large (L-HDL rem ) and small (S-HDL rem ) species, and lipid-poor apoA-I. Here we characterized the composition and morphology of remodeled HDL species and compared their ability to efflux cholesterol via different transporters. Methods and Results: CSL112 and HDL3, fluorescently labeled on protein or lipid, were incubated together for varying periods of time at 37°C. Resultant HDL particle size distribution was assessed by native gel electrophoresis followed by fluorescence imaging. Morphology of the individual purified products of HDL remodeling was examined by negative stain electron microscopy. We show that L-HDL rem is a large, spherical species composed of apoA-I and phospholipid from both native HDL and CSL112. S-HDL rem is a small, disc-shaped species composed of apoA-I from CSL112 that is smaller due to the loss of phospholipids. The smallest species, lipid-poor apoA-I, is composed of apoA-I from HDL and CSL112. Lipid-poor apoA-I and S-HDL rem were found to have the greatest ability to efflux cholesterol via ABCA1. While S-HDL rem and L-HDL rem showed comparable ability to efflux cholesterol via ABCG1, L-HDL rem mediated additional efflux via SR-B1 and by an aqueous diffusion process. Conclusion: The generation of these remodeled HDL species can account for the strong and immediate increase in cholesterol efflux capacity observed upon infusion of CSL112, and make CSL112 a promising approach for rapidly removing cholesterol from atherosclerotic plaque.