Objective-LDL oxidation is believed to play an important role in the development of atherosclerosis, and oxidized LDL particles have been shown to become targets for the immune system. Immunization of animals with oxidized LDL results in reduction of atherosclerosis, suggesting an atheroprotective effect of this immune response. Methods and Results-Using a polypeptide library covering the complete sequence of apoB-100, a large number of native and malondialdehyde-modified peptide sequences in apoB-100 that are recognized by antibodies in human plasma were identified. We report here that immunization with apoB-100 peptide sequences, against which high levels of IgG and IgM antibodies are present in healthy human controls, reduce atherosclerosis in apoE-null mice by about 60%.Immunizations with these peptides were also found to increase the collagen content of subvalvular lesions. Conclusions-These studies have identified peptide sequences in apoB-100 that induce immune responses, which inhibits atherosclerosis. This suggests a way of developing an immunization therapy for coronary heart disease. Key Words: apolipoproteins Ⅲ atherosclerosis Ⅲ immunization Ⅲ mice Ⅲ peptides A ccumulation, aggregation, and modification of LDL particles in the arterial intima are believed to be among the most important initiating factors in atherosclerosis. 1,2 Oxidative modification of LDLs trapped in the vascular extracellular matrix is associated with generation of a number of highly reactive compounds, such as lysophosphatidylcholine, lipid peroxides, aldehydes, and oxysterols, that cause cell damage and local inflammation. 2,3 In general terms, the development of raised fibromuscular plaques can be said to represent a repair response to the vascular injury and oxidized lipids may be one factor causing such injury. 4 Several protective mechanisms exist to limit injury caused by oxidatively damaged LDL particles. One involves the removal of oxidized LDL by macrophage scavenger receptors. 5,6 Recent studies suggest a second protective mechanism involving specific immune responses against epitopes present in oxidized LDLs. These were initially identified in studies of hypercholesterolemic rabbits, in which immunization with oxidized LDL was found to reduce atherosclerosis by 40% to 60%. 7,8 Similar observations were subsequently also made in apoE-null and LDL receptor-null mice, 9 -11 as well as in balloon-injured hypercholesterolemic rabbits. 12 In apoE-null mice, induction of hypercholesterolemia by a high-fat diet results in a dramatic increase in autoantibodies against oxidized LDLs. Circulating autoantibodies against oxidized LDLs are also abundant in humans and have been shown to correlate with severity of disease in cardiovascular patients. [13][14][15][16] These findings suggest the possibility of developing new treatments against atherosclerosis based on selective activation of atheroprotective immune responses against oxidized LDL antigens.Oxidation of LDL is associated with formation of reactive aldehydes, such as malondi...

Background-Accumulation and oxidation of LDL are believed to be important initiating factors in atherosclerosis.Oxidized LDL is recognized by the immune system, and animal studies have suggested that these immune responses have a protective effect against atherosclerosis. Aldehyde-modified peptide sequences in apolipoprotein B-100 (apoB-100) are major targets for these immune responses. Methods and Results-Human IgG1 antibodies against 2 malondialdehyde (MDA)-modified apoB-100 peptide sequences were produced through screening of a single-chain antibody-fragment library and subsequent cloning into a pcDNA3 vector. Three weekly doses of these antibodies were injected into male apoE Ϫ/Ϫ mice. Phosphate-buffered saline and human IgG1 antibodies against fluorescein isothiocyanate were used as controls. One of the IgG1 antibodies significantly and dose-dependently reduced the extent of atherosclerosis as well as the plaque content of oxidized LDL epitopes and macrophages. In cell culture studies, human monocytes were incubated with native LDL or oxidized LDL, in the presence of antibodies. The same antibody induced an increase in monocyte binding and uptake of oxidized LDL. Conclusions-These findings suggest that antibodies are important mediators of atheroprotective immune responses directed to oxidized LDL. Thus, passive immunization against MDA-modified apoB-100 peptide sequences may represent a novel therapeutic approach for prevention and treatment of cardiovascular disease.

Human IgG1 against a specific oxLDL epitope can induce rapid and substantial regression of atherosclerotic lesions, possibly by stimulating lipid efflux and inhibiting macrophage recruitment. These recombinant human antibodies could represent a novel strategy for rapid regression/stabilization of atherosclerotic lesions.

Immunization with MDA apo B-100 fragments induce a shift from Th1 to a Th2 specific oxidized LDL antibody expression, but without a concomitant downregulation of plaque IFN-gamma expression.

Objectives. Autoantibodies to apolipoprotein (apo) B-100 peptides are present in human plasma and have been shown to be associated with decreased cardiovascular risk. The present study aimed to determine if apo B-100 peptide vaccines are atheroprotective in mice expressing human apo B-100 and if the effectiveness of the vaccines is influenced by the level of pre-existing peptide-specific autoantibodies.Design. LDL receptor ) ⁄ ) ⁄ human apo B-100 transgenic mice were immunized with native human apo B-100 peptides p45 or p210 at 6, 9 and 11 weeks and the extent of atherosclerosis determined by en face Oil Red O staining of the aorta at 25 weeks. Autoantibody levels were determined by enzyme-linked immunosorbent assay, and RNA expression in the spleen was assessed by real time PCR.Results. Control mice had high levels of autoantibodies against p210 but only low levels against p45. Immunization with native p45 and p210 reduced atherosclerosis by 66% (P < 0.02) and 59% (P = 0.06), respectively. The atheroprotective effect of apo B peptide immunization occurred in the absence of an increase in peptide-specific IgG, but was associated with an increase in IgM recognizing native and copper-oxidized LDL.Conclusions. Immunization with apo B peptide-based vaccines inhibits atherosclerosis in mice expressing human apo B-100 suggesting that they can interact with their target as expressed in humans. The protective effect is independent of the pre-existing level of apo B peptide autoantibodies and can occur without activating an increase in peptide-specific antibodies suggesting that atheroprotection can be mediated by cellular immune responses.

Objectives. Autoimmune responses against oxidized low-density lipoprotein are considered to play an important pro-inflammatory role in atherosclerosis and to promote disease progression. T-regulatory cells (Tregs) are immunosuppressive cells that have an important part in maintaining self-tolerance and protection against autoimmunity. We investigated whether aBp210, a prototype atherosclerosis vaccine based on a peptide sequence derived from apolipoprotein B, inhibits atherosclerosis through the activation of Tregs.Design. Six-week-old Apoe ) ⁄ ) mice were immunized with aBp210 and received booster immunizations 3 and 5 weeks later, as well as 1 week before being killed at 25 weeks of age.Results. At 12 weeks, immunized mice had increased expression of the Treg marker CD25 on circulating CD4 cells, and concanavalin A (Con A)-induced interferon-c, interleukin (IL)-4, and IL-10 release from splenocytes was markedly depressed. At 25 weeks, there was a fivefold expansion of splenic CD4+ CD25+ Foxp3 Tregs, a 65% decrease in Con Ainduced splenic T-cell proliferation and a 37% reduction in the development of atherosclerosis in immunized mice. Administration of blocking antibodies against CD25 neutralized aBp210-induced Treg activation as well as the reduction of atherosclerosis. Conclusions. The present findings demonstrate that immunization of Apoe) ⁄ ) mice with the apolipoprotein B peptide vaccine aBp210 is associated with activation of Tregs. Administration of antibodies against CD25 results in depletion of Tregs and blocking of the atheroprotective effect of the vaccine. Modulation in atherosclerosis-related autoimmunity by antigenspecific activation of Tregs represents a novel approach for treatment of atherosclerosis.

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ObjectiveIL-25 has been implicated in the initiation of type 2 immunity and in the protection against autoimmune inflammatory diseases. Recent studies have identified the novel innate lymphoid type 2 cells (ILC2s) as an IL-25 target cell population. The purpose of this study was to evaluate if IL-25 has any influence on atherosclerosis development in mice.Methods and ResultsAdministration of 1 μg IL-25 per day for one week to atherosclerosis-prone apolipoprotein (apo)E deficient mice, had limited effect on the frequency of T cell populations, but resulted in a large expansion of ILC2s in the spleen. The expansion was accompanied by increased levels of anti-phosphorylcholine (PC) natural IgM antibodies in plasma and elevated levels of IL-5 in plasma and spleen. Transfer of ILC2s to apoE deficient mice elevated the natural antibody-producing B1a cell population in the spleen. Treatment of apoE/Rag-1 deficient mice with IL-25 was also associated with extensive expansion of splenic ILC2s and increased plasma IL-5, suggesting ILC2s to be the source of IL-5. Administration of IL-25 in IL-5 deficient mice resulted in an expanded ILC2 population, but did not stimulate generation of anti-PC IgM, indicating that IL-5 is not required for ILC2 expansion but for the downstream production of natural antibodies. Additionally, administration of 1 μg IL-25 per day for 4 weeks in apoE deficient mice reduced atherosclerosis in the aorta both during initiation and progression of the disease.ConclusionsThe present findings demonstrate that IL-25 has a protective role in atherosclerosis mediated by innate responses, including ILC2 expansion, increased IL-5 secretion, B1a expansion and natural anti-PC IgM generation, rather than adaptive Th2 responses.