ApoB-Specific CD4+ T Cells in Mouse and Human Atherosclerosis.

Atherosclerosis is a chronic inflammatory condition of the arterial wall that leads to the formation of vessel-occluding plaques within the subintimal space of middle-sized and larger arteries. While traditionally understood as a myeloid-driven lipid-storage disease, growing evidence suggests that the accumulation of low-density lipoprotein cholesterol (LDL-C) ignites an autoimmune response with CD4+ T-helper (TH) cells that recognize self-peptides from Apolipoprotein B (ApoB), the core protein of LDL-C. These autoreactive CD4+ T cells home to the atherosclerotic plaque, clonally expand, instruct other cells in the plaque, and induce clinical plaque instability. Recent developments in detecting antigen-specific cells at the single cell level have demonstrated that ApoB-reactive CD4+ T cells exist in humans and mice. Their phenotypes and functions deviate from classical immunological concepts of distinct and terminally differentiated TH immunity. Instead, ApoB-specific CD4+ T cells have a highly plastic phenotype, can acquire several, partially opposing and mixed transcriptional programs simultaneously, and transit from one TH subset into another over time. In this review, we highlight adaptive immune mechanisms in atherosclerosis with a focus on CD4+ T cells, introduce novel technologies to detect ApoB-specific CD4+ T cells at the single cell level, and discuss the potential impact of ApoB-driven autoimmunity in atherosclerosis.

Developing Electron Microscopy Tools for Profiling Plasma Lipoproteins Using Methyl Cellulose Embedment, Machine Learning and Immunodetection of Apolipoprotein B and Apolipoprotein(a).

Plasma lipoproteins are important carriers of cholesterol and have been linked strongly to cardiovascular disease (CVD). Our study aimed to achieve fine-grained measurements of lipoprotein subpopulations such as low-density lipoprotein (LDL), lipoprotein(a) (Lp(a), or remnant lipoproteins (RLP) using electron microscopy combined with machine learning tools from microliter samples of human plasma. In the reported method, lipoproteins were absorbed onto electron microscopy (EM) support films from diluted plasma and embedded in thin films of methyl cellulose (MC) containing mixed metal stains, providing intense edge contrast. The results show that LPs have a continuous frequency distribution of sizes, extending from LDL (> 15 nm) to intermediate density lipoprotein (IDL) and very low-density lipoproteins (VLDL). Furthermore, mixed metal staining produces striking "positive" contrast of specific antibodies attached to lipoproteins providing quantitative data on apolipoprotein(a)-positive Lp(a) or apolipoprotein B (ApoB)-positive particles. To enable automatic particle characterization, we also demonstrated efficient segmentation of lipoprotein particles using deep learning software characterized by a Mask Region-based Convolutional Neural Networks (R-CNN) architecture with transfer learning. In future, EM and machine learning could be combined with microarray deposition and automated imaging for higher throughput quantitation of lipoproteins associated with CVD risk.

A clinically applicable adjuvant for an atherosclerosis vaccine in mice.

Vaccination with MHC-II-restricted peptides from Apolipoprotein B (ApoB) with complete and incomplete Freund's adjuvant (CFA/IFA) is known to protect mice from atherosclerosis. This vaccination induces antigen-specific IgG1 and IgG2c antibody responses and a robust CD4 T cell response in lymph nodes. However, CFA/IFA cannot be used in humans. To find a clinically applicable adjuvant, we tested the effect of vaccinating Apoe-deficient mice with ApoB peptide P6 (TGAYSNASSTESASY). In a broad screening experiment, Addavax, a squalene-based oil-in-water adjuvant similar to MF59, was the only adjuvant that showed similar efficacy as CFA/IFA. This was confirmed in a confirmation experiment for both the aortic arch and whole aorta analyzed by en face analysis after atherosclerotic lesion staining. Mechanistically, restimulated peritoneal cells from mice immunized with P6 in Addavax released significant amounts of IL-10. Unlike P6 in CFA/IFA, vaccination with P6 in Addavax did not induce any detectable IgG1 or IgG2c antibodies to P6. These data suggest that squalene-based adjuvants such as MF59 are good candidate adjuvants for developing a clinically effective atherosclerosis vaccine.

Regulatory CD4+ T Cells Recognize Major Histocompatibility Complex Class II Molecule-Restricted Peptide Epitopes of Apolipoprotein B.

BACKGROUND: CD4+ T cells play an important role in atherosclerosis, but their antigen specificity is poorly understood. Immunization with apolipoprotein B (ApoB, core protein of low density lipoprotein) is known to be atheroprotective in animal models. Here, we report on a human APOB peptide, p18, that is sequence-identical in mouse ApoB and binds to both mouse and human major histocompatibility complex class II molecules. METHODS: We constructed p18 tetramers to detect human and mouse APOB-specific T cells and assayed their phenotype by flow cytometry including CD4 lineage transcription factors, intracellular cytokines, and T cell receptor activation. Apolipoprotein E-deficient ( Apoe-/-) mice were vaccinated with p18 peptide or adjuvants alone, and atherosclerotic burden in the aorta was determined. RESULTS: In human peripheral blood mononuclear cells from donors without cardiovascular disease, p18 specific CD4+ T cells detected by a new human leukocyte antigen-antigen D related-p18 tetramers were mostly Foxp3+ regulatory T cells (Tregs). Donors with subclinical cardiovascular disease as detected by carotid artery ultrasound had Tregs coexpressing retinoic acid-related orphan receptor gamma t or T-bet, which were both almost absent in donors without cardiovascular disease. In Apoe-/- mice, immunization with p18 induced Tregs and reduced atherosclerotic lesions. After peptide restimulation, responding CD4+ T cells identified by Nur77-GFP (green fluorescent protein) were highly enriched in Tregs. A new mouse I-Ab-p18 tetramer identified the expansion of p18-specific CD4+ T cells on vaccination, which were enriched for interleukin-10-producing Tregs. CONCLUSIONS: These findings show that APOB p18-specific CD4+ T cells are mainly Tregs in healthy donors, but coexpress other CD4 lineage transcription factors in donors with subclinical cardiovascular disease. This study identifies ApoB peptide 18 as the first Treg epitope in human and mouse atherosclerosis.

Atheroprotective vaccination with MHC-II-restricted ApoB peptides induces peritoneal IL-10-producing CD4 T cells.

Although immunization with major histocompatibility complex (MHC) class II-restricted apolipoprotein B (ApoB) peptides has been shown to be atheroprotective, the mechanism is unclear. Here, we investigated CD4+ T cell populations in immunized atherosclerotic mice. Peptides (16-mers) from mouse ApoB, the core protein of low-density lipoprotein (LDL), were screened for binding to I-Ab by computer prediction and confirmed by radiolabeled peptide competition. Three new peptides, P101 (FGKQGFFPDSVNKALY, 5.5 nM IC50), P102 (TLYALSHAVNSYFDVD, 6.8 nM), and P103 (LYYKEDKTSLSASAAS, 95 nM), were tested in an atherosclerosis model (Apoe-/- mice on Western diet). Immunization with each of the three peptides (1 time in complete Freund's adjuvant subcuntaneously and 4 time in incomplete Freund's adjuvant intraperitoneally) but not with adjuvant alone showed significantly reduced atherosclerotic plaques in the aortic root by serial sections and in the whole aorta by en face staining. There were no differences in body weight, LDL cholesterol, or triglycerides. Peritoneal leukocytes from ApoB peptide-immunized mice, but not control mice, secreted significant amounts of IL-10 (150 pg/ml). Flow cytometry showed that peptide immunization induced IL-10 in 10% of peritoneal CD4+ T cells, some of which also expressed chemokine (C-C motif) receptor 5 (CCR5). Vaccination with ApoB peptides expanded peritoneal FoxP3+ regulatory CD4+ T cells and more than tripled the number of CCR5+FoxP3+ cells. Similar trends were also seen in the draining mediastinal lymph nodes but not in the nondraining inguinal lymph nodes. We conclude that vaccination with MHC class II-restricted autologous ApoB peptides induces regulatory T cells (Tregs) and IL-10, suggesting a plausible mechanism for atheroprotection.NEW & NOTEWORTHY Vaccination against apolipoprotein B (ApoB), the protein of LDL, attracts attention as a novel approach to prevent atherosclerosis. We discovered major histocompatibility complex class II-restricted ApoB peptides, which reduce atherosclerosis and induce IL-10-producing CD4+ T cells and chemokine (C-C motif) receptor 5 expression on regulatory T cells, suggesting that immunization with ApoB peptides inhibits atherosclerosis by inducing anti-inflammatory cytokines.

Ultrastructural organisation of HCV from the bloodstream of infected patients revealed by electron microscopy after specific immunocapture.

OBJECTIVE: HCV particles are associated with very low-density lipoprotein components in chronically infected patients. These hybrid particles, or 'lipo-viro particles' (LVPs), are rich in triglycerides, and contain the viral RNA, the capsid protein, E1E2 envelope glycoproteins and apolipoproteins B and E. However, their specific ultrastructural organisation has yet to be determined. We developed a strategy for the preparation of any viral sample that preserves the native structure of the LVPs, facilitating their precise morphological characterisation. DESIGN: Using a strategy based on the direct specific immunocapture of particles on transmission electron microscopy (TEM) grids, we characterised the precise morphology of the viral particle by TEM. RESULTS: The LVP consists of a broad nucleocapsid surrounding an electron-dense centre, presumably containing the HCV genome. The nucleocapsid is surrounded by an irregular, detergent-sensitive crescent probably composed of lipids. Lipid content may determine particle size. These particles carry HCV E1E2, ApoB and ApoE, as shown in our immuno-EM analysis. Our results also suggest that these putative LVPs circulate in the serum of patients as part of a mixed population, including lipoprotein-like particles and complete viral particles. CONCLUSIONS: Twenty-five years after the discovery of HCV, this study finally provides information about the precise morphological organisation of viral particles. It is truly remarkable that our TEM images fully confirm the ultrastructure of LVPs predicted by several authors, almost exclusively from the results of molecular biology studies.

Monocyte-induced recovery of inflammation-associated hepatocellular dysfunction in a biochip-based human liver model.

Liver dysfunction is an early event in sepsis-related multi-organ failure. We here report the establishment and characterization of a microfluidically supported in vitro organoid model of the human liver sinusoid. The liver organoid is composed of vascular and hepatocyte cell layers integrating non-parenchymal cells closely reflecting tissue architecture and enables physiological cross-communication in a bio-inspired fashion. Inflammation-associated liver dysfunction was mimicked by stimulation with various agonists of toll-like receptors. TLR-stimulation induced the release of pro- and anti-inflammatory cytokines and diminished expression of endothelial VE-cadherin, hepatic MRP-2 transporter and apolipoprotein B (ApoB), resulting in an inflammation-related endothelial barrier disruption and hepatocellular dysfunction in the liver organoid. However, interaction of the liver organoid with human monocytes attenuated inflammation-related cell responses and restored MRP-2 transporter activity, ApoB expression and albumin/urea production. The cellular events observed in the liver organoid closely resembled pathophysiological responses in the well-established sepsis model of peritoneal contamination and infection (PCI) in mice and clinical observations in human sepsis. We therefore conclude that this human liver organoid model is a valuable tool to investigate sepsis-related liver dysfunction and subsequent immune cell-related tissue repair/remodeling processes.

Serum Lipoproteins Are Critical for Pulmonary Innate Defense against Staphylococcus aureus Quorum Sensing.

Hyperlipidemia has been extensively studied in the context of atherosclerosis, whereas the potential health consequences of the opposite extreme, hypolipidemia, remain largely uninvestigated. Circulating lipoproteins are essential carriers of insoluble lipid molecules and are increasingly recognized as innate immune effectors. Importantly, severe hypolipidemia, which may occur with trauma or critical illness, is clinically associated with bacterial pneumonia. To test the hypothesis that circulating lipoproteins are essential for optimal host innate defense in the lung, we used lipoprotein-deficient mice and a mouse model of Staphylococcus aureus pneumonia in which invasive infection requires virulence factor expression controlled by the accessory gene regulator (agr) operon. Activation of agr and subsequent virulence factor expression is inhibited by apolipoprotein B, the structural protein of low-density lipoprotein, which binds and sequesters the secreted agr-signaling peptide (AIP). In this article, we report that lipoprotein deficiency impairs early pulmonary innate defense against S. aureus quorum-sensing-dependent pathogenesis. Specifically, apolipoprotein B levels in the lung early postinfection are significantly reduced with lipoprotein deficiency, coinciding with impaired host control of S. aureus agr-signaling and increased agr-dependent morbidity (weight loss) and inflammation. Given that lipoproteins also inhibit LTA- and LPS-mediated inflammation, these results suggest that hypolipidemia may broadly impact posttrauma pneumonia susceptibility to both Gram-positive and -negative pathogens. Together with previous reports demonstrating that hyperlipidemia also impairs lung innate defense, these results suggest that maintenance of normal serum lipoprotein levels is necessary for optimal host innate defense in the lung.

Estrogen receptor signal in regulation of B cell activation during diverse immune responses.

The role of signalling through oestrogen receptors (ERs) in the regulation of B cell activation is an area of growing importance not only in terms protective immunity but also in the determination of the mechanisms of the onset of autoimmune disorders and cancers. The mode of signalling action of this single chain nuclear receptor protein molecule depends on its ability to bind to the promoters of Pax5, HOXC4 and apolipoprotein B RNA-editing enzyme activation-induced cytidine deaminase (AID) genes. ER-mediated transcriptional regulation induces class switch recombination of the immunoglobulin heavy chain variable (VH) to DH-JH genes and somatic hypermutation in developing B cells. The mode of action of ER is associated with BCR-signal pathways that involve the regulator proteins BAFF and APRIL. Additionally, the plasma membrane-bound G protein-coupled oestrogen receptor-1 (GEPR1) directs diverse cell signalling events in B cells that involve the MAPK pathways. These signals are immensely important during progenitor and precursor B cell activation. We have focused our goals on the medicinal aspects of ER-signalling mechanisms and their effects on polyclonal B cell activation.

Heritability of Biomarkers of Oxidized Lipoproteins: Twin Pair Study.

OBJECTIVE: To determine whether biomarkers of oxidized lipoproteins are genetically determined. Lipoprotein(a) (Lp[a]) is a heritable risk factor and carrier of oxidized phospholipids (OxPL). APPROACH AND RESULTS: We measured oxidized phospholipids on apolipoprotein B-containing lipoproteins (OxPL-apoB), Lp(a), IgG, and IgM autoantibodies to malondialdehyde-modified low-density lipoprotein, copper oxidized low-density lipoprotein, and apoB-immune complexes in 386 monozygotic and dizygotic twins to estimate trait heritability (h(2)) and determine specific genetic effects among traits. A genome-wide linkage study followed by genetic association was performed. The h(2) (scale: 0-1) for Lp(a) was 0.91±0.01 and for OxPL-apoB 0.87±0.02, which were higher than physiological, inflammatory, or lipid traits. h(2) of IgM malondialdehyde-modified low-density lipoprotein, copper oxidized low-density lipoprotein, and apoB-immune complexes were 0.69±0.04, 0.67±0.05, and 0.80±0.03, respectively, and for IgG malondialdehyde-modified low-density lipoprotein, copper oxidized low-density lipoprotein, and apoB-immune complexes 0.62±0.05, 0.52±0.06, and 0.53±0.06, respectively. There was an inverse correlation between the major apo(a) isoform and OxPL-apoB (R=-0.49; P<0.001) and Lp(a) (R=-0.48; P<0.001) and OxPL-apoB was modestly correlated with Lp(a) (ρ=0.57; P<0.0001). The correlation in major apo(a) isoform size was concordant (R=1.0; P<0.001) among monozygotic twins but not dizygotic twins (R=0.40; P=0.055). Lp(a) and OxPL-apoB shared genetic codetermination (genetic covariance, ρG=0.774±0.032; P=1.09×10(-38)), although not environmental determination (environmental covariance, ρE=0.081±0.15; P=0.15). In contrast, Lp(a) shared environmental but not genetic codetermination with autoantibodies to malondialdehyde-modified low-density lipoprotein and copper oxidized low-density lipoprotein, and apoB-immune complexes. Sib-pair genetic linkage of the Lp(a) trait revealed that single nucleotide polymorphism rs10455872 was significantly associated with OxPL-apoB after adjusting for Lp(a). CONCLUSIONS: OxPL-apoB and other biomarkers of oxidized lipoproteins are highly heritable cardiovascular risk factors that suggest novel genetic origins of atherothrombosis.

A study of IgG antibodies to the ApoB protein in non-ST segment elevation acute coronary syndrome.

OBJECTIVES: It has long been noted that there is an association of antibodies against oxidized low-density lipoprotein (oxLDL) with cardiovascular disease, but the anti-oxLDL antibody has not been confirmed as a biomarker for prediction of acute coronary syndrome (ACS). Apolipoprotein B (ApoB) may carry the epitopes for the immune response to oxLDL. The present work was thus undertaken to detect circulating antibodies to ApoB in non-ST segment elevation ACS (NSTE-ACS). DESIGN: A total of 130 patients with NSTE-ACS and 201 control subjects were recruited. Six ApoB-derived peptipe antigens (Ag1-Ag6) were used to develop an in-house enzyme-linked immunosorbent assay to examine circulating anti-ApoB IgG levels. RESULTS: The anti-Ag1 IgG level was significantly higher in the patient group than the control group (P < 0.001) and the non-ST segment elevation myocardial infarction appeared to be the main form of NSTE-ACS contributing to the increased levels of anti-Ag1 IgG (P < 0.001); there was no significant alteration in the levels of IgG to the other 5 antigens in NSTE-ACS. CONCLUSIONS: Circulating anti-ApoB IgG test may be useful for prediction of NSTE-ACS although further confirmation is needed in large-scale clinical studies.

Highly sensitive immunoassay based on SERS using nano-Au immune probes and a nano-Ag immune substrate.

A super-high-sensitivity immunoassay based on surface-enhanced Raman scattering (SERS) was implemented using the nano-Au immune probes and nano-Ag immune substrate. Ultraviolet-visible extinction spectra, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images, and SERS spectra were used to characterise the nano-Au immune probes and the nano-Ag immune substrate. The nano-Ag immune substrate was prepared by the in situ growth of Ag nanoparticles and the subsequent linkage of these nanoparticles with anti-apolipoprotein B on a silicon wafer. The nano-Ag immune substrate exhibited strong SERS activity, excellent reproducibility, and high biospecificity. The nano-Au immune probes were prepared by immobilising 4-mercaptobenzoic acid (4MBA) molecules as a Raman reporter and anti-apolipoprotein B onto the surfaces of Au nanoparticles. It was found that 4MBA induced the aggregation of Au nanoparticles, resulting in the generation of vast hot spots. Moreover, the nano-Au immune probes exhibited strong SERS activity and high biospecificity. A sandwich-type immunoassay structure consisting of the nano-Au immune probes and nano-Ag immune substrate was used to detect the concentration of apolipoprotein B, where the detection limit was as low as 2 fg/mL (3.878×10(-18) mol/L). Taken together, the experimental results indicate that the proposed immunoassay protocol has a great potential application in biological sensing and clinical diagnostics.

Development and partial characterisation of an antiserum against apolipoprotein B of the short-finned eel, Anguilla australis.

Despite its key role in transportation of triacylglycerides in blood, the distribution, localisation and molecular weight variants of apolipoprotein B (Apob) in teleost fish have essentially escaped study. To address this, a specific short-finned eel (Anguilla australis) Apob antiserum was produced by an immunised rabbit, purified and partially characterised. Localisation of Apob at both the mRNA (in situ hybridisation) and protein (immunohistochemistry) levels mirrored that of mammals; thus immunostaining was confined to the interstitial spaces of the liver and the vascular core of the intestinal villi. Immunostaining of proteins by Western blotting, followed by high-resolution LC-MS, indicated that peptide sequence coverage of Apob in low-density lipoproteins spanned the full-length protein. We conclude that only full-length Apob is produced by eels and that both liver and intestine are key sites for its synthesis.

The associations of oxidized high-density lipoprotein lipids with risk factors for atherosclerosis: the Cardiovascular Risk in Young Finns Study.

Scavenging and reverse transport of atherogenic oxidized lipids by high-density lipoprotein (HDL) was recently suggested to contribute to atheroprotection. We investigated the associations of oxidized HDL lipids (oxHDLlipids) with known risk factors for atherosclerosis in a population-based cross-sectional study of 1395 Finnish adults ages 24-39 years (54.9% women). Analysis of oxidized lipids in isolated HDL and LDL (oxLDLlipids) was based on the determination of conjugated dienes. Oxidized LDL was measured also with a method based on antibodies against oxidized Apo-B (oxLDLprot). Serum lipids and risk factors were measured. In multivariable models, oxHDLlipids were associated inversely with age (partial R(2)=2.9% in men, 0.8% in women) and directly with oxLDLlipids (partial R(2)=3.4% in men, 4.2% in women) after adjustment for Apo-A1 (partial R(2)=9.6% in men, 25.2% in women). In men, oxHDLlipids were also associated inversely with insulin (partial R(2)=1.1%). In women, oxHDLlipids were additionally inversely associated with waist circumference (partial R(2)=1.8%) and daily smoking (partial R(2)=0.7%) and directly with C-reactive protein (CRP; partial R(2)=0.5%) and alcohol use (partial R(2)=0.5%). We conclude that an elevated risk profile characterized primarily by advanced age is associated with lower oxHDLlipid levels in a population of young Finnish men and women. Higher levels of oxHDLlipids are additionally associated with higher oxLDLlipid levels. In men, higher insulin levels are also associated with lower oxHDLlipid levels. In women, increased waist circumference and daily smoking are also associated with lower oxHDLlipid levels, and higher CRP levels and alcohol use are associated with higher oxHDLlipid levels.

Human plasma anti-α-galactoside antibody forms immune complex with autologous lipoprotein(a).

Anti-α-galactoside antibody (anti-Gal) from human plasma that bound to α-galactoside-bearing guar galactomannan gel and was eluted with specific sugar (affinity-purified anti-Gal ; APAG) invariably contained apo(a) and apo B subunits in a proportion close to that in plasma lipoprotein(a) [Lp(a)]. Since LDL does not contain apo(a), result suggested Lp(a) as a component of APAG. Lp(a) in APAG was complexed with anti-Gal since plate-coated anti-apo(a) captured Lp(a) along with the antibody. Association of Lp(a) with anti-Gal in APAG was considerably lower in presence of anti-Gal-specific sugar, suggesting that Lp(a) occupied the sugar-binding site of anti-Gal. Content of Lp(a)-bound anti-Gal in APAG, though a minor fraction of total antibody, increased steadily with total Lp(a) content of plasma. Further, Lp(a) released from immune complex-rich fraction of plasma by anti-Gal- specific sugar was proportional to total plasma Lp(a). Anti-Gal titre decreased with increasing Lp(a) concentration among 114 plasma samples. Results indicate the potential of anti-Gal molecules with its binding site partially occupied by Lp(a) molecule(s) to a) use the remaining binding site(s) to recognize other macromolecules or cells and b) transport Lp(a) across Fc receptor-bearing cells.

Immunological detection of large oxidized lipoproteins in hypertriglyceridemic serum.

BACKGROUND: Triglyceride-rich, low-density lipoproteins (TG-rich LDL) have been reported as an oxidized lipoprotein species in patients with severe liver disease. Using TG-rich LDL as an immunogen, we obtained a monoclonal antibody (G11-6) that reacted with TG-rich LDL from patients with liver disease and with metal-oxidized LDL only in the early process of the oxidation reaction. This study determined the G11-6-reactive lipoproteins in hypertriglyceridemic serum. METHODS: Serum samples from healthy volunteers (n = 12) and hypertriglyceridemic patients (n = 9) were fractionated by gel filtration and subjected to a sandwich enzyme-linked immunosorbent assay (ELISA) using G11-6 and polyclonal anti-apolipoprotein B antibodies. RESULTS: Small LDL and larger lipoproteins reacted with G11-6. G11-6-reactive small LDL was identified in both the healthy subjects and hypertriglyceridemic patients, whereas G11-6-reactive larger lipoproteins were found only in the hypertriglyceridemic patients. CONCLUSIONS: G11-6 is a useful tool for detecting increased large oxidized lipoproteins in hypertriglyceridemic patients.

Obesity modulates the immune response to oxidized LDL in hypertensive patients.

Obesity and hypertension have been recognized as inflammatory diseases capable of activating the immune system, thus contributing to an increased cardiovascular risk. However, the link between adaptive immunity, obesity, and hypertension is poorly understood. We investigated the relationship of the body mass index (BMI) on the inflammatory, vascular, and immune responses in patients with hypertension naïve of anti-hypertensive treatment. Hypertensive patients (N = 88) were divided into three groups: normal weight (NW), overweight (OW), and obese (OB) subjects. Anti-oxidized LDL autoantibodies (anti-oxLDL Abs), anti-ApoB-D peptide (anti-ApoB-D) Abs, interleukin (IL)-8 and IL-10, flow-mediated dilation (FMD) of the brachial artery, and 24-h ambulatory blood pressure monitoring (ABPM) were assessed. OB patients presented lower levels of anti-oxLDL Abs and IL-10, higher levels of IL-8, and impaired FMD, when compared to NW and OW (P < 0.05), without differences between groups regarding anti-ApoB-D Abs. After adjusting for age, systolic and diastolic blood pressure, anti-oxLDL Abs were inversely correlated with BMI and waist circumference (r = -0.24, P = 0.02 and r = -0.25, P = 0.02, respectively), whereas ApoB-D correlated with 24-h ABPM (r = 0.22, P = 0.05 for systolic, and r = 0.29, P = 0.01 for diastolic blood pressure). Regression analyses showed inverse associations of anti-oxLDL Abs with BMI (ß = -0.05, P = 0.01) and waist circumference (ß = -0.01, P = 0.02); anti-ApoB-D Abs were associated with systolic and diastolic 24-h ABPM (ß = 0.96, P = 0.04; ß = 1.02, P = 0.005, for systolic and diastolic 24-h ABPM, respectively). Among hypertensive patients, obesity modulates the immune and inflammatory milieu, determining an unfavorable balance of cytokines and reduction in titers of anti-oxLDL Abs. Twenty-four hour ABPM is associated with titers of anti-ApoB-D Abs.

Mucosal tolerance to a combination of ApoB and HSP60 peptides controls plaque progression and stabilizes vulnerable plaque in Apob(tm2Sgy)Ldlr(tm1Her)/J mice.

Oral tolerance to auto antigens reduces the development of atherosclerosis in mouse models. However, the effect of immune tolerance to multiple self antigenic peptides in plaque progression and stabilization is not known. We studied the protective effect of mucosal tolerance to peptides from apolipoprotein B (ApoB; 661-680) and heat shock protein 60 (HSP60; 153-163), in combination with diet, in the prevention of atherosclerotic lesion progression and plaque stabilization in ApoB(tm25gy)LDLr(tm1Her) mice. We found that oral administration of five doses of a combination of ApoB and HSP60 peptides (20 µg/mice/dose) induced tolerance to both the peptides and reduced early plaque development by 39.9% better than the individual peptides (ApoB = 28.7%;HSP60 = 26.8%)(P<0.001). Oral tolerance to combination of peptides along with diet modification arrested plaque progression by 37.6% which was associated with increases in T-regulatory cell and transforming growth factor-ß expression in the plaque and peripheral circulation. Reduced macrophage infiltration and tumor necrosis factor-α expression in the plaque was also observed. Tolerance with continued hypercholesterolemia resulted in 60.8% reduction in necrotic core area suggesting plaque stabilization, which was supported by reduction in apoptosis and increased efferocytosis demonstrated by greater expression of receptor tyrosine kinase Mer (MerTK) in the plaque. Tolerance to the two peptides also reduced the expression of matrix metalloproteinase 9, tissue factor, calprotectin, and increased its collagen content. Our study suggests that oral tolerance to ApoB and HSP60 peptide combination induces CD4(+) CTLA4(+) Tregs and CD4(+)CD25(+)Foxp3(+) Tregs secreting TGF-ß, which inhibit pathogenic T cell response to both peptides thus reducing the development and progression of atherosclerosis and provides evidence for plaque stabilization in ApoB(tm25gy)LDLr(tm1Her) mice.

Monoclonal antibodies against lipopolysaccharide of Chlamydia trachomatis with cross reactivity to human ApoB.

Splenocytes obtained from mice immunized with whole purified elementary bodies of Chlamydia trachomatis were used for hybridoma construction. The resulting clones were screened with ELISA using chlamydial lipopolysaccharide (LPS) and full-length human apolipoprotein B (ApoB). One analyzed clone producing IgG1 (MAb 7B5) showed simultaneous recognition of chlamydial LPS and human ApoB, suggesting the presence of common antigenic epitopes in their structures. MAb 7B5 exhibited agreeable activity in immunoblot analysis conducted using chlamydial extracts or full-length human ApoB as well as in immunofluorescence (IF) detecting typical inclusion bodies of C. trachomatis and C. pneumoniae in the infected eukaryotic host cells. The removal of LPS from chlamydial suspensions with lauroyl sarcosyl led to a complete disappearance of IF associated with the elementary bodies of C. trachomatis. Therefore, immunologic response to chlamydial antigen may be associated with the generation of ApoB-specific antibody. Molecular mimicry and subsequent formation of cross-reactive antibodies might be an essential mechanism explaining the appearance of circulating auto-antibodies against low density lipoproteins (LDL) in patients with atherosclerosis. Moreover, newly generated MAb 7B5 can be a useful tool in the laboratory diagnosis of chlamydial infections.

Immuno-electron cryo-microscopy imaging reveals a looped topology of apoB at the surface of human LDL.

A single copy of apoB is the sole protein component of human LDL. ApoB is crucial for LDL particle stabilization and is the ligand for LDL receptor, through which cholesterol is delivered to cells. Dysregulation of the pathways of LDL metabolism is well documented in the pathophysiology of atherosclerosis. However, an understanding of the structure of LDL and apoB underlying these biological processes remains limited. In this study, we derived a 22 Å-resolution three-dimensional (3D) density map of LDL using cryo-electron microscopy and image reconstruction, which showed a backbone of high-density regions that encircle the LDL particle. Additional high-density belts complemented this backbone high density to enclose the edge of the LDL particle. Image reconstructions of monoclonal antibody-labeled LDL located six epitopes in five putative domains of apoB in 3D. Epitopes in the LDL receptor binding domain were located on one side of the LDL particle, and epitopes in the N-terminal and C-terminal domains of apoB were in close proximity at the front side of the particle. Such image information revealed a looped topology of apoB on the LDL surface and demonstrated the active role of apoB in maintaining the shape of the LDL particle.