Immunization with cholesterol-rich liposomes induces anti-cholesterol antibodies and reduces diet-induced hypercholesterolemia and plaque formation

Abstract

Immunization of rabbits with a protein-free formulation consisting of liposomes containing 71% cholesterol and lipid A as an adjuvant induced anticholesterol antibodies that caused complement-dependent lysis of liposomes lacking lipid A. The antibodies, immunoglobulin G (IgG) and immunoglobulin M (IgM), also recognized nonoxidized crystalline cholesterol as an antigen by enzyme-linked immunosorbent assay (ELISA). The effects of immunization against cholesterol on elevations in serum cholesterol and development of atherosclerosis were examined in rabbits fed a diet containing 0.5% to 1.0% cholesterol. Although the mean serum cholesterol level, mainly in the form of very-low-density lipoprotein cholesterol, rose as much as 60-fold in the nonimmunized rabbits, the elevation was significantly less--as much as 35% lower--in the immunized rabbits. Elevation of serum cholesterol was accompanied by an apparent drop in the level of antibodies on initiating the diet, followed by a rebound on stopping the diet, thus suggesting that the antibodies were adsorbed to cholesterol that was present in circulating lipoproteins. When lipoprotein fractions--composed of either very-low-density and intermediate-density lipoproteins derived from cholesterol-fed nonimmunized rabbits or human low-density lipoproteins--were tested as capture antigens by solid-phase ELISA, reactivity was observed with IgG and IgM antibodies present in the serum of immunized rabbits. Immunization also resulted in a marked decrease in the risk of developing atherosclerosis. Analysis of aortic atherosclerosis by quantitative histologic examination and fatty streaks by automated morphometric probability-of-occurrence mapping showed diminished atherosclerosis in most areas of the aorta in vaccine recipients. It is proposed that immunization with liposomes containing 71% cholesterol and lipid A can reduce diet-induced hypercholesterolemia and atherosclerosis.

Novel anti-cholesterol monoclonal immunoglobulin G antibodies as probes and potential modulators of membrane raft-dependent immune functions

“…A putative role of ACHAs in atherosclerosis, induced by a cholesterol-rich diet, can be postulated from results of experiments with rabbit models (7).…”

Cholesterol crystal binding of biliary immuno-globulin A: visualization by fluorescence light microscopy

“…This hypothesis is supported by the synthesis of specific antibodies against cholesterol upon injection of cholesterol-rich liposomes in rabbits and mice [32,33] . These antibodies recognize non-oxidized crystalline cholesterol [32] , and analyses by solid-phase ELISA revealed that human sera contain varying levels of naturally occurring autoantibodies to cholesterol [34] . Similarly, humans might synthesize and secrete specific IgA antibodies to cholesterol into bile.…”

Advances in immune-modulating therapies to treat atherosclerotic cardiovascular diseases

“…Several other groups of investigators subsequently reported similar atheroprotective effects by active immunization with cholesterol-rich liposomes in cholesterol-fed rabbits [Alving et al 1996], MDAmodified LDL in apoE(-/-) mice [George et al 1998b] or with plaque homogenates or MDAmodified LDL in apoE(-/-) mice [Zhou et al 2001].…”