Ingrid Söderberg

Inhibition of Atherosclerosis in ApoE-Null Mice by Immunization with ApoB-100 Peptide Sequences

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.

Recombinant human antibodies against aldehyde-modified apolipoprotein B-100 peptide sequences inhibit atherosclerosis

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−/− 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.

Atheroprotective immunization with MDA-modified apo B-100 peptide sequences is associated with activation of Th2 specific antibody expression.

Objective: The objective of this study was to evaluate if immunization with MDA-modified human apo B-100 fragments is associated with a shift in the Th1/Th2 balance. Methods and Results: Apo E deficient mice were immunized with one of the peptides (P45; amino acids 688–707, P74; amino acids 1123–1142 or P240; amino acids 3613–3632) at 6, 9 and 11 weeks of age and compared to controls given carrier alone. Immunization with P45 and P74 reduced atherosclerosis in the aorta of 25-week-old mice by 48% (p=0.02) and 31% (p=0.06) and macrophage content in atherosclerotic plaques by 33% (p=0.02) and 39% (p=0.02), respectively. The levels of Th2-specific IgG1 against each peptide increased more than 50-fold in response to immunization, whereas the levels of specific IgM and Th1-associated IgG2a were only marginally affected. However, there was an increase in the plaque expression of both Th1 and Th2 cytokines as assessed by real time PCR. Immunization with P240, a non-homologous peptide used as control, induced a 10-fold increase of specific IgG1 but did not influence atherosclerosis or plaque content. Conclusions: 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-γ expression.

Treatment with apo B peptide vaccines inhibits atherosclerosis in human apo B-100 transgenic mice without inducing an increase in peptide-specific antibodies

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.

Evidence for a role of regulatory T cells in mediating the atheroprotective effect of apolipoprotein B peptide vaccine

Abstract.  Wigren M, Kolbus D, Dunér P, Ljungcrantz I, Söderberg I, Björkbacka H, Fredrikson GN, Nilsson J. (Malmö University Hospital, Lund University; Malmö University, Malmo; Sweden) Evidence for a role of regulatory T cells in mediating the atheroprotective effect of apolipoprotein B peptide vaccine. J Intern Med 2011; 269: 546–556.

Non-ionic sugar-based surfactants: Self assembly and air/water interfacial activity

Abstract The air/water interfacial activity and self-assembly of the mono-dodecyl esters of glucose, sucrose, raffinose and stachyose have been investigated. These four non-ionic surfactants provide a series where the hydrocarbon chain length is invariant while the surfactant headgroup sequentially increases in size. The minimum area per surfactant molecule at the air/water interface increases smoothly with the sequential addition of galactose structural units, sucrose β followed by an L α phase as the temperature is increased. At a low weight percentage of surfactant, the other three surfactants form isotropic micellar phases. At relatively higher weight percentages of surfactant, the sucrose surfactant forms hexagonal and L β phases, the raffinose surfactant forms discrete cubic micellar and hexagonal phases, and the stachyose surfactant begins to crystallize. At a very high weight percentage of surfactant, the sucrose, raffinose and stachyose surfactants exist as hydrated crystals. Most of the self-assembly behaviour in water can be readily explained in terms of the geometric packing constraints.

Humoral Immune Response Against Defined Oxidized Low-Density Lipoprotein Antigens Reflects Structure and Disease Activity of Carotid Plaques

Background—Immune responses against oxidized low-density lipoprotein (LDL) play an important role in atherosclerosis. The aim of this study was to investigate if humoral immune response against specific oxidized LDL antigens, such as aldehyde-modified peptide sequences of apolipoprotein B-100, reflects disease activity and structure of atherosclerotic plaques. Methods and Results—Plaques were obtained from 114 symptomatic subjects referred to carotid endarterectomy and characterized immunohistochemically and histologically. Plasma levels of IgG and IgM against aldehyde-modified apolipoprotein B-100 amino acid sequences 661 to 680, 3136 to 3155 (peptide 210), and 3661 to 3680 (peptide 240) were determined by enzyme-linked immunosorbent assay. High levels of IgG against peptide 210 were associated with increased plaque content of lipids (r=0.24, P<0.05) and hemorrhage (r=0.27, P=0.005), with decreased content of fibrous tissue (r=−0.25, P=0.01), but also with lower total plaque volume (r=−0.21, P<0.05). In contrast, high levels of IgM against peptide 240 were associated with plaques with more fibrous tissue (r=0.35, P<0.001), less lipids (r=−0.34, P<0.001), and less macrophages (r=−0.24, P<0.05). IgM against peptide 210 were found to be associated with plaque fibrous tissue (r=0.20, P<0.05), less lipids (r=−0.21, P<0.05), and less macrophages (r=−0.27, P=0.01). Conclusion—These findings support the notion that immune responses against oxidized LDL epitopes are involved in atherosclerosis and that the level of circulating antibodies against these structures may reflect disease activity in the arterial wall.

TAP1-Deficiency Does Not Alter Atherosclerosis Development in Apoe(-/-) Mice.

Antigen presenting cells (APC) have the ability to present both extra-cellular and intra-cellular antigens via MHC class I molecules to CD8+ T cells. The cross presentation of extra-cellular antigens is reduced in mice with deficient Antigen Peptide Transporter 1 (TAP1)-dependent MHC class I antigen presentation, and these mice are characterized by a diminished CD8+ T cell population. We have recently reported an increased activation of CD8+ T cells in hypercholesterolemic Apoe−/− mice. Therefore, this study included TAP1-deficient Apoe−/− mice (Apoe−/−Tap1−/−) to test the atherogenicity of CD8+ T cells and TAP1-dependent cross presentation in a hypercholesterolemic environment. As expected the CD8+ T cell numbers were low in Apoe−/−Tap1−/− mice in comparison to Apoe−/− mice, constituting ∼1% of the lymphocyte population. In spite of this there were no differences in the extent of atherosclerosis as assessed by en face Oil Red O staining of the aorta and cross-sections of the aortic root between Apoe−/−Tap1−/− and Apoe−/− mice. Moreover, no differences were detected in lesion infiltration of macrophages or CD3+ T cells in Apoe−/−Tap1−/− compared to Apoe−/− mice. The CD3+CD4+ T cell fraction was increased in Apoe−/−Tap1−/− mice, suggesting a compensation for the decreased CD8+ T cell population. Interestingly, the fraction of CD8+ effector memory T cells was increased but this appeared to have little impact on the atherosclerosis development. In conclusion, Apoe−/−Tap1−/− mice develop atherosclerosis equal to Apoe−/− mice, indicating a minor role for CD8+ T cells and TAP1-dependent antigen presentation in the disease process.

IL-25 Inhibits Atherosclerosis Development in Apolipoprotein E Deficient Mice

Objective IL-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 Results Administration 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. Conclusions The 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.

IL-22 affects smooth muscle cell phenotype and plaque formation in apolipoprotein E knockout mice

OBJECTIVE IL-22 is a recently discovered cytokine that belongs to the family of IL-10 related cytokines. It is produced by activated T-cells and innate lymphoid cells and has been suggested to be involved in tissue repair. As both inflammation and repair play important roles in atherosclerosis we investigated if IL-22 deficiency influences the disease process in Apoe(-/-) mice. METHODS We generated IL-22(-/-)Apoe(-/-) mice and fed them high-fat-diet for 14 weeks to characterize atherosclerosis development. RESULTS IL-22(-/-)Apoe(-/-) mice exhibited reduced plaque size both in the aorta (p = 0.0036) and the aortic root compared (p = 0.0012) with Apoe(-/-) controls. Moreover, plaque collagen was reduced in IL-22(-/-)Apoe(-/-) mice (p = 0.02) and this was associated with an increased expression of smooth muscle cell (SMC)-α-actin (p = 0.04) and caldesmon (p = 0.016) in the underlying media. Carotid arteries from IL-22(-/-)Apoe(-/-) mice displayed increased expression of genes associated with a contractile SMC phenotype e.g. α-actin (p = 0.004) and caldesmon (p = 0.03). Arterial SMCs were shown to express the IL-22 receptor and in vitro exposure to IL-22 resulted in a down-regulation of alpha actin and caldesmon gene expression in these cells. CONCLUSION Our observations demonstrate that IL-22 is involved in plaque formation and suggest that IL-22 released by immune cells is involved in activation of vascular repair by stimulating medial SMC dedifferentiation into a synthetic phenotype. This response contributes to plaque growth by enabling SMC migration into the intima but may also help to stabilize the plaque.