Identification of Immune Responses Against Aldehyde-Modified Peptide Sequences in ApoB Associated With Cardiovascular Disease

Abstract

Objective-Atherosclerosis is associated with an immune response against oxidized LDL, which modulates the progression of the disease process. Methods and Results-Using a library of polypeptides covering the complete sequence of apoB-100, the only major protein of LDL, we have identified over 100 different human antibodies reacting against aldehyde-modified apoB-100 sequences. IgM antibody titer levels decreased with age and were associated with the intima-media thickness of the carotid artery in subjects younger than 60 years. There were also inverse associations between IgM levels and oxidized LDL in plasma. In prospective clinical studies, antibody levels against several aldehyde-modified apoB-100 sites were associated with cardiovascular disease in this age group. Whether this immune response is adaptive (protective) or maladaptive (causal) in atherosclerosis requires further investigation. Conclusions-We have characterized a large number of epitopes within the apoB-100 component of oxidized LDL that provoke an immune response in humans. These findings will make it possible to study the role of immune responses against specific sites in oxidized LDL and to determine whether these immune responses influence the risk for future cardiac events.

Recombinant Human Antibodies Against Aldehyde-Modified Apolipoprotein B-100 Peptide Sequences Inhibit Atherosclerosis

“…2 Autoantibodies against several such MDA-modified apoB-100 peptides have been found in humans. 11 The present studies show that human IgG1 generated against one of these MDA peptide sequences reduces atherosclerosis in apoE Ϫ/Ϫ mice and that this is associated with reduced accumulation of the corresponding oxLDL-associated epitope and of macrophages in atherosclerotic plaques.…”

“…11 Single-chain human antibody fragments with specificity for MDA-modified apoB-100 -derived peptides P45 (IEIGLEGKGFEPTLEALFGK, amino acids 661 to 680) or P210 (KTTKQSFDLSVKAQYKKNKH, amino acids 3136 to 3155) were selected from the single-chain fragment-variable (scFv) n-CoDeR library, essentially as described earlier. 13 In brief, 3 consecutive rounds of selection were performed with 10 pmol of MDA-modified peptide bound to a solid phase.…”

“…9,10 Using a library of malondialdehyde (MDA)-modified polypeptides covering the complete amino acid sequence of human apoB-100, we have recently identified a large number of epitopes recognized by antibodies present in human plasma. 11 The levels of several of these antibodies show an inverse association with plasma oxLDL, suggesting that antibodies are involved in the clearance of these particles. Immunization of apoE Ϫ/Ϫ mice with the corresponding human apoB peptides was found to result in reduced plaque formation and a stable plaque phenotype, as indicated by increased collagen content.…”

Low levels of IgG autoantibodies against the apolipoprotein B antigen p210 increases the risk of cardiovascular death after carotid endarterectomy

“…These are nationwide validated registers where all causes of death and more than 99 % of all somatic (including surgery) and psychiatric hospital discharges are registered. 19 In doubtful cases, information was checked through telephone interviews and review of the medical charts. All deaths were verified against the Swedish National Population Register.…”

“…19 Briefly EDTA-plasma was supplemented with the anti-oxidants diethylenetriaminepentaacetic acid (DTPA) and butylated hydroxytoluene (BHT). In the beginning, the 96-holes plates (Nunc MaxiSorp, Nunc, Roskilde, Denmark) were coated at a concentration of 20 mg/ml with the following peptides: native p210 and MDA-modified p210 6 (TAG Copenhagen A/S, Copenhagen, Denmark), and incubated overnight at 4 ˚C.…”