Antibodies of IgM subclass to phosphorylcholine and oxidized LDL are protective factors for atherosclerosis in patients with hypertension

Natural Antibodies as Rheostats for Susceptibility to Chronic Diseases in the Aged

Natural antibodies are spontaneously produced in the absence of infection or immunization, and are both anti-microbial and autoreactive. Autoreactive natural antibodies can bind noxious molecules, such as those involved in clinical situations of atherosclerosis (oxLDL), malignancy (NGcGM3), and neurodegeneration (amyloid, tau) and can affect the fate of their targets or the cells bearing them to maintain homeostasis. Clinically relevant natural antibodies have been shown to decline with advancing age in those few situations where measurements have been made. Consistent with this, human B-1 cells that are thought to be responsible for generating natural antibodies also decline with advancing age. These findings together suggest that an age-related decline in amount or efficacy of homeostatic natural antibodies is associated with relative loss of protection against molecules involved in several diseases whose incidence rises in the older age population, and that those individuals experiencing greatest loss are at greatest risk. In this view, natural antibodies act as rheostats for susceptibility to several age-related diseases. These considerations suggest that administration of natural antibodies, or of factors that maintain B-1 cells and/or enhance production of natural antibodies by B-1 cells, may serve to counteract the onset or progression of age-related chronic illness.

Simvastatin Efficiently Lowers Small LDL-IgG Immune Complex Levels: A Therapeutic Quality beyond the Lipid-Lowering Effect

We investigated a polyethylene glycol non-precipitable low-density lipoprotein (LDL) subfraction targeted by IgG and the influence of statin therapy on plasma levels of these small LDL-IgG-immune complexes (LDL-IgG-IC). LDL-subfractions were isolated from 6 atherosclerotic subjects and 3 healthy individuals utilizing iodixanol density gradient ultracentrifugation. Cholesterol, apoB and malondialdehyde (MDA) levels were determined in each fraction by enzymatic testing, dissociation-enhanced lanthanide fluorescence immunoassay and high-performance liquid chromatography, respectively. The levels of LDL-IgG-IC were quantified densitometrically following lipid electrophoresis, particle size distribution was assessed with dynamic light scattering and size exclusion chromatography. The influence of simvastatin (40 mg/day for three months) on small LDL-IgG-IC levels and their distribution among LDL-subfractions (salt gradient separation) were investigated in 11 patients with confirmed coronary artery disease (CAD). We demonstrate that the investigated LDL-IgG-IC are small particles present in atherosclerotic patients and healthy subjects. In vitro assembly of LDL-IgG-IC resulted in particle density shifts indicating a composition of one single molecule of IgG per LDL particle. Normalization on cholesterol levels revealed MDA values twice as high for LDL-subfractions rich in small LDL-IgG-IC if compared to dominant LDL-subfractions. Reactivity of affinity purified small LDL-IgG-IC to monoclonal antibody OB/04 indicates a high degree of modified apoB and oxidative modification. Simvastatin therapy studied in the CAD patients significantly lowered LDL levels and to an even higher extent, small LDL-IgG-IC levels without affecting their distribution. In conclusion simvastatin lowers levels of small LDL-IgG-IC more effectively than LDL-cholesterol and LDL-apoB levels in atherosclerotic patients. This antiatherogenic effect may additionally contribute to the known beneficial effects of this drug in the treatment of atherosclerosis.

Phosphorylcholine antibodies are diminished in ANCA-associated vasculitis

BACKGROUND/AIM

ANCA-associated (AAV) vasculitis is an autoimmune small-vessel vasculitis and may be associated with accelerated atherosclerosis as suggested by current literature. Antibodies against oxidized lipoproteins (OxLDL) and phosphorylcholine (Pc) protect from atherosclerosis. This study characterizes these antibodies in AAV.

METHODS

Pc- and anti-OxLDL antibodies were determined in sera of 39 AAV patients and 44 healthy controls (HC). Intima-media thickness (IMT, carotids) and pulse wave velocity (PWV, A. femoralis) were measured.

RESULTS

Pc-/OxLDL IgM antibodies were significantly reduced in AAV. IMT and PWV were negatively associated with anti-Pc antibodies in HC only.

CONCLUSION

Atheroprotective anti-Pc/anti-OxLDL antibodies are significantly reduced in AAV possibly explaining accelerated atherosclerosis in vasculitis patients.

Circulating autoantibodies against the apolipoprotein B-100 peptides p45 and p210 in relation to the occurrence of carotid plaques in 64-year-old women

Objectives

Immune responses against oxidized low density lipoprotein (LDL) play a key role in atherosclerosis. Previous studies have indicated inverse associations between autoantibodies to epitopes in oxidized LDL and cardiovascular disease. In this study we investigated the associations between autoantibodies against the apolipoprotein B-100 (apoB-100) peptides p45 and p210 and occurrence of carotid plaques.

Design

The study cohort consisted of a population-based sample of 64-year-old women with varying degrees of glucose tolerance (n=594). To identify and record the occurrence of carotid atherosclerotic plaques ultrasonography was used. Measurements of plasma IgM and IgG autoantibodies against the native and malondialdehyde (MDA)-modified apoB-100 peptides p45 and p210 were performed by ELISA.

Results

Women with carotid plaques were found to have lower levels of IgM MDA-p210 autoantibodies compared to plaque-free women. The number of carotid plaques in each subject and the total carotid plaque area correlated inversely with IgM MDA-p210 levels (r=-0.11, P=0.009 and r=-0.11, P=0.013, respectively). Furthermore, levels of IgM MDA-p210 above the lowest tertile were associated with an odds ratio of 0.55 (95% CI 0.38-0.79, P=0.001) for occurrence of carotid plaques, independently of other risk markers and statin treatment. Associations between apo-B100 peptide autoantibodies and cardiovascular risk factors were generally weak but subjects with impaired glucose tolerance had higher levels of IgM against MDA-p210.

Conclusion

The present study demonstrates that high levels of IgM against MDA-p210 are associated with less severe carotid disease in women. These findings provide additional support for a role of immune responses against oxidized LDL in cardiovascular disease.

The immunomodulatory parasitic worm product ES-62 reduces lupus-associated accelerated atherosclerosis in a mouse model

ES-62 is an anti-inflammatory phosphorylcholine-containing glycoprotein secreted by the filarial nematode Acanthocheilonema viteae. Accelerated atherosclerosis frequently occurs in systemic lupus erythematosus, resulting in substantial cardiovascular morbidity and mortality. We examined the effects of ES-62 in the gld.apoE(-/-) mouse model of this condition. Treatment with ES-62 did not substantially modulate renal pathology but caused decreased anti-nuclear autoantibody levels. Moreover, a striking 60% reduction in aortic atherosclerotic lesions was observed, with an associated decrease in macrophages and fibrosis. We believe that these latter findings constitute the first example of a defined parasitic worm product with therapeutic potential in atherosclerosis: ES-62-based drugs may represent a novel approach to control accelerated atherosclerosis in systemic lupus erythematosus.

Autoantibodies to phosphorylcholine and cardiovascular outcomes in patients with acute coronary syndromes in the ATLAS ACS-TIMI 46 trial

Atherogenesis is a complex inflammatory process stemming from the accumulation and oxidation of low density lipoproteins (LDL). IgM autoantibodies against phosphorylcholine (anti-PC) bind to the PC epitope on oxidized LDL (OxLDL), inhibiting the uptake of oxLDL by macrophages in atherosclerotic lesions. Anti-PC autoantibodies have been reported to be protective against atherothrombosis. We investigated the relationship of anti-PC concentrations with cardiovascular outcomes in patients with acute coronary syndromes (ACS). We measured anti-PC levels within 7 days of an ACS in 3,356 patients enrolled in the ATLAS ACS-TIMI 46 trial, a randomized dose ranging study of rivaroxaban versus placebo. The primary endpoint was death, myocardial infarction (MI), stroke, or severe recurrent ischemia (SRI) requiring revascularization during 6 months. The median baseline anti-PC concentration was 40.9 U/mL (25th, 75th percentiles: 25.4, 67.4). There was no significant association between anti-PC levels and the primary endpoint (Q1: 6.8 %, Q2: 4.2 %, Q3: 7.8 %, Q4: 5.4 %, p-trend = 0.87), all-cause mortality (Q1: 1.4 %, Q2: 0.7 %, Q3: 2.4 %, Q4: 0.9 %, p-trend = 0. 96), or any of the other individual endpoint components (MI: p-trend = 0.87, Stroke: p-trend = 0.43, SRI: p-trend = 0.66). Using the previously reported anti-PC cutpoint of 17 U/mL did not reveal a significant relationship between anti-PC concentrations and cardiovascular outcomes (<17 U/mL: 8.1 % vs. ≥17 U/mL: 5.8 %; p = 0.11). Similarly, evaluation of anti-PC as a continuous variable did not reveal a significant association (p = 0.30). In this study of patients early after ACS undergoing intensive secondary preventive therapy, IgM anti-PC titers did not exhibit a significant relationship with cardiovascular outcomes.

Malondialdehyde-Modified LDL IgG Antibody Levels and Indices of Cardiac Function in Valvular Heart and Coronary Artery Disease Patients

OBJECTIVE

To compare the changes in anti-malondialdehyde-modified low-density lipoprotein (MDA-LDL) IgG levels among patients undergoing off-pump and on-pump coronary artery bypass grafting (CABG) or valvuloplasty.

SUBJECTS AND METHODS

A total of 38, 39 and 34 patients who underwent off-pump CABG, on-pump CABG and valvuloplasty, respectively, were enrolled in this study. Serum anti-MDA-LDL IgG values were measured 24 h before and after the operative procedures and at discharge. Echocardiography was also done before surgery and before discharge. The results were compared with values from 50 healthy controls.

RESULTS

In all patients, a reduction in antibody titers was observed post-operatively. However, the decrease was significant only in the off-pump CABG - before surgery: 42.33 (25.83-58.51), after surgery: 30.86 (16.36-51.33) and at discharge: 10.96 (6.82-23.57; p = 0.027). There was a significant positive association between anti-MDA-LDL IgG levels and ejection fraction (r = 0.248, p = 0.036) and a negative association with E/E', a marker of pulmonary capillary wedge pressure, in the coronary patients (r = -0.345, p = 0.012), but no significant associations were found in patients with valvular heart disease.

CONCLUSIONS

Serum anti-MDA-LDL IgG levels were associated with cardiac function indices in coronary patients undergoing CABG.

Antibodies against native and oxidized cardiolipin and phosphatidylserine and phosphorylcholine in atherosclerosis development

Background

Antibodies against cardiolipin and phosphatidylserine (anti-CL and anti-PS) are associated with thrombosis. In contrast, we determined that IgM antibodies against oxidized CL and PS (OxCL and OxPS) and phosphorylcholine (anti-PC) could be protection markers for cardiovascular disease (CVD).

Methods

226 individuals with established hypertension (diastolic pressure>95 mmHg) from the European Lacidipine Study on Atherosclerosis. Antibodies were tested by ELISA. As a surrogate measure of atherosclerosis, the mean of the maximum intima-media thicknesses (IMT) in the far walls of common carotids and bifurcations was determined by ultrasonography at the time of inclusion and 4 years following inclusion.

Results

Increases in IMT measures at follow-up were significantly less common in subjects which at baseline had high IgM anti-OxPS and anti-PC at above 75^th percentile: OR 0,45, CI (0,23–0,86) and OR 0.37, CI (0,19–0,71), p = 0.0137 respectively and above 90^th percentile: OR 0.32, CI (0,12–0,84) and OR 0.39, CI (0,15–1.00), p = 0.050 and OR 0,22, CI (0,08–0,59) p = 0,0029. IgM anti-OxCL was negatively associated with IMT increases (OR, 0.32, CI (0,12–0,84), p = 0231). There were no associations for IgM anti-PS or anti-CL. Anti-PC, as determined herein by a commercial ELISA, was strongly associated with data from our previously published in house ELISA (R = 0,87; p<0,0001).) Anti-PC was also a risk marker at low levels (below 25^th percentile; OR = 2,37 (1,16–4,82), p = 0,0177).

Conclusions

High levels of IgM anti-OxPS and anti-OxCL, but not traditional anti-phospholipid antibodies (anti-PS and anti-CL), are associated with protection against atherosclerosis development. In addition, low IgM anti-PC was a risk marker but high a protection marker.

IgM-antibodies against phosphorylcholine in mothers and normal or low birth weight term newborn infants

OBJECTIVE

To determine levels of athero-protective IgM antibodies against phosphorylcholine in mothers and term-born normal or low birth weight infants.

APPROACH

Twenty three mother-infant pairs were studied, of whom 16 infants were within the normal weight range for gestational age (NGA; 3652[504] g) and 7 were small for gestational age (SGA; birth weight: 2715[255] g), the latter <2SD below the Swedish reference data mean for normal fetal growth. All infants were born at term (mean ± SD 40.5 ± 1.1 weeks). Serum was available from 6 mothers with SGA and 14 with NGA infants. Participating mothers were aged 34.0 ± 3.9 years (no difference between groups). Fourteen neonates were boys and seven were girls. Levels of anti-PC IgM were determined by ELISA.

RESULTS

Neonatal IgM anti-PC levels were low (undetectable in 8 infants out of which 3 were SGA) with a median of 76[range 0-2.51] U/ml. Maternal IgM anti-PC levels were significantly higher (median 7198[range: 25.32-656.0]) U/ml) and the proportion of mothers in highest quartile (>75th percentile) was larger in mothers of NGA-infants (43%) vs. those of SGA-infants (0%, p = 0.032).

CONCLUSIONS

IgM anti-PC levels are low at birth, which suggests that these antibodies do not play a "housekeeping" role in immune function during fetal life/development, but arise predominately on exposure to external antigens after birth. Furthermore, low maternal IgM anti-PC levels may play a role in placental insufficiency, contributing to poor fetal growth and a small-for-date baby. This preliminary observation may have implications for the future risk of atherosclerosis/cardiovascular disease development in pregnant women and their offspring.

Low levels of natural IgM antibodies against phosphorylcholine are independently associated with vascular remodeling in patients with coronary artery disease

Low anti-phosphorylcholine (PC) IgM plasma levels have been associated with increased incidence of adverse events in coronary artery disease (CAD). The underlying mechanisms are unclear. We hypothesized that atheroprotection mediated by anti-PC IgM antibodies is associated with reduced vascular remodeling and therefore tested whether anti-PC IgM plasma levels independently predict vascular remodeling. In a prospective cross-sectional study, anti-PC IgM plasma levels were measured in 175 consecutive patients with suspected CAD undergoing cardiac computed tomography angiography. Plaque morphology was thoroughly analyzed. Vascular remodeling was defined by a change in the vessel diameter at the plaque site in comparison to the reference segment proximal to the lesion (reference diameter) of ≥10%. Mean age of the patients was 64.8 ± 10.7 years, 48.6% were female. In 98 patients CAD was diagnosed, 57 (58.2%) of which displayed non-obstructive CAD (stenosis <50%), whereas 41 (41.8%) exhibited obstructive CAD (stenosis ≥50%). In 34 of 98 (34.7%) CAD patients vascular remodeling was present. Mean anti-PC IgM levels did not differ between patients with and without CAD (70.8 ± 52.7 vs. 69.1 ± 55.1 U/mL). However, anti-PC IgM levels were significantly lower in CAD patients compared to those without vascular remodeling (46.6 ± 31.6 vs. 73.3 ± 58.5 U/mL, P = 0.024). Using multivariate logistic regression, anti-PC IgM plasma levels independently predicted coronary vascular remodeling (HR 0.322, 95% confidence interval 0.121-0.856, P = 0.023). In conclusion, low anti-PC IgM levels are independently associated with coronary vascular remodeling. These findings may represent the link between in vitro studies demonstrating atheroprotective effects of anti-PC IgM and clinical data demonstrating that low anti-PC IgM levels are associated with adverse outcome in CAD patients.

Low levels of IgM antibodies against phosphorylcholine are associated with fast carotid intima media thickness progression and cardiovascular risk in men

OBJECTIVE

Low levels of IgM anti-phosphorylcholine (anti-PC) increase the risk of cardiovascular events (CVE). Here we investigate the association of low anti-PC with the progression of carotid intima media thickness (C-IMT) and incidence of CVE in a large cohort of individuals at high risk of CVE, the IMPROVE, a prospective multicenter European study.

METHODS

3711 subjects (54-79 years) with at least three established cardiovascular risk factors were enrolled. Baseline serum levels of IgM anti-PC were measured by ELISA. Carotid ultrasound investigations were performed at baseline and after 15 and 30 months of follow-up. The risk of C-IMT progression and ischemic CVE associated with low anti-PC levels was tested by logistic regression and Cox regression analysis, respectively. Risk estimates were adjusted by center and conventional cardiovascular risk factors.

RESULTS

3670 study participants were included in the present analysis and 213 CVE were recorded during a 3 year follow up. Anti-PC levels (U/ml) were classified into quartiles [Q1≤ 40, Q2 >40-≤64, Q3 >64-≤102, Q4 >102]. In men, low levels of anti-PC (Q1) were associated with the highest (>90th) percentile of the fastest C-IMT progression, i.e. the segment showing the fastest progression over 30 months in the whole carotid tree, with an OR of 1.41 (95%CI, 1.02-1.9) and with an increased risk of CVE with a multivariable adjusted HR of 1.85 (95%CI, 1.1-3.1). No significant associations were found in women.

CONCLUSIONS

Low anti-PC levels increase the risk of CVE in men. This effect may be partly mediated by a fast C-IMT progression.

Human monoclonal Fab and human plasma antibodies to carbamyl-epitopes cross-react with malondialdehyde-adducts

Oxidized low-density lipoprotein (OxLDL) plays a crucial role in the development of atherosclerosis. Carbamylated LDL has been suggested to promote atherogenesis in patients with chronic kidney disease. Here we observed that plasma IgG and IgM antibodies to carbamylated epitopes were associated with IgG and IgM antibodies to oxidation-specific epitopes (ρ = 0·65-0·86, P < 0·001) in healthy adults, suggesting a cross-reaction between antibodies recognizing carbamyl-epitopes and malondialdehyde (MDA)/malondialdehyde acetaldehyde (MAA) -adducts. We used a phage display technique to clone a human Fab antibody that bound to carbamylated LDL and other carbamylated proteins. Anti-carbamyl-Fab (Fab106) cross-reacted with oxidation-specific epitopes, especially with MDA-LDL and MAA-LDL. We showed that Fab106 bound to apoptotic Jurkat cells known to contain these oxidation-specific epitopes, and the binding was competed with soluble carbamylated and MDA-/MAA-modified LDL and BSA. In addition, Fab106 was able to block the uptake of carbamyl-LDL and MDA-LDL by macrophages and stained mouse atherosclerotic lesions. The observed cross-reaction between carbamylated and MDA-/MAA-modified LDL and its contribution to enhanced atherogenesis in uraemic patients require further investigation.

Naturally occurring human phosphorylcholine antibodies are predominantly products of affinity-matured B cells in the adult

Phosphorylcholine (PC) is a classic T-independent Ag that is exposed on apoptotic cells, oxidized phospholipids, and bacterial polysaccharides. Experimental as well as epidemiological studies have over the past decade implicated Abs against PC (anti-PC) as anti-inflammatory and a strong protective factor in cardiovascular disease. Although clinically important, little is known about the development of anti-PC in humans. This study was conceived to dissect the human anti-PC repertoire and generate human mAbs. We designed a PC-specific probe to identify, isolate, and characterize PC-reactive B cells from 10 healthy individuals. The donors had all mounted somatically mutated Abs toward PC using a broad variety of Ig genes. PC-reactive B cells were primarily found in the IgM(+) memory subset, although significant numbers also were detected among naive, IgG(+), and CD27(+)CD43(+) B cells. Abs from these subsets were clonally related, suggesting a common origin. mAbs derived from the same donors exhibited equivalent or higher affinity for PC than the well-characterized murine T-15 clone. These results provide novel insights into the cellular and molecular ontogeny of atheroprotective PC Abs, thereby offering new opportunities for Ab-based therapeutic interventions.

Natural IgM: beneficial autoantibodies for the control of inflammatory and autoimmune disease

Natural IgM are highly represented in the circulation at birth, and these often autoreactive antibodies have been postulated to have innate-like properties and play crucial roles in apoptotic cell clearance, tissue homeostasis, and immune modulation. This review summarizes the known properties of these IgM autoantibodies, and the evidence that these anti-apoptotic cell IgM natural antibodies can regulate inflammatory responses through ancient pathways of the innate immune system that first arose long before the initial emergence of the adaptive immune system. While the regulatory contributions of these natural IgM autoantibodies are certainly not an essential and fundamental component of host defenses, these provide an additional layer to further protect the host. More importantly, these IgM antibody responses are highly inducible and their up-regulation can be a powerful means for the host to survive in a setting of chronic inflammation. The observed beneficial clinical associations for cardiovascular disease and autoimmunity, as well as opportunities for potential therapeutic implications are discussed.

Plasma IgA antibody levels to malondialdehyde acetaldehyde-adducts are associated with inflammatory mediators, obesity and type 2 diabetes

AIM

Obesity and type 2 diabetes (T2D) associate with increased oxidative stress. Malondialdehyde acetaldehyde (MAA) adducts have been suggested to be one of the antigenic epitopes in MDA-LDL responsible for the antibody recognition. Our aim was to investigate the associations between plasma IgA antibodies to MAA-LDL, inflammatory markers, adipokines, obesity, and T2D.

METHODS

IgA to MAA-LDL were measured in a subsample (n = 1507) of the Finnish Health 2000 survey. The associations between antibody levels, obesity, TNF-α, IL-6, high-sensitivity (hs) CRP, resistin, adiponectin, fasting plasma (fp) glucose, fp-insulin, glycosylated hemoglobin (Hb-A1C), and T2D were investigated.

RESULTS

IgA to MAA-LDL associated positively with fasting plasma insulin. IgA to MAA-LDL were higher among subjects with T2D (P < 0.001) compared to subjects with normal glucose metabolism. IgA to MAA-LDL associated with obesity, but was not independently (P = 0.002, not significant after correction for multiple tests) associated with T2D in logistic regression analysis. IgA to MAA-LDL, obesity, and TNF-α all associated with markers of glucose metabolism.

CONCLUSIONS

T2D subjects had increased IgA to MAA-LDL compared to subjects with normal glucose metabolism. The data suggest that the associations between IgA to MAA-LDL and markers of glucose metabolism were independent of TNF-α but dependent on components of the metabolic syndrome.

Immune mechanisms in atherosclerosis, especially in diabetes type 2

Atherosclerosis and ensuing cardiovascular disease (CVD) are major complications of diabetes type 2. Atherosclerosis is a chronic inflammatory condition involving immunocompetent cells of different types present in the lesions. Even though inflammation and immune activation may be more pronounced in atherosclerosis in diabetes type 2, there does not appear to be any major differences between diabetics and non-diabetics. Similar factors are thus implicated in atherosclerosis-associated immune activation in both groups. The cause of immune activation is not known and different mutually non-exclusive possibilities exist. Oxidized and/or enzymatically modified forms of low-density lipoprotein (OxLDL) and dead cells are present in atherosclerotic plaques. OxLDL could play a role, being pro-inflammatory and immunostimulatory as it activates T-cells and is cytotoxic at higher concentrations. Inflammatory phospholipids in OxLDL are implicated, with phosphorylcholine (PC) as one of the exposed antigens. Antibodies against PC (anti-PC) are anti-atherogenic in mouse studies, and anti-PC is negatively associated with development of atherosclerosis and CVD in humans. Bacteria and virus have been discussed as potential causes of immune activation, but it has been difficult to find direct evidence supporting this hypothesis, and antibiotic trials in humans have been negative or inconclusive. Heat shock proteins (HSP) could be one major target for atherogenic immune reactions. More direct causes of plaque rupture include cytokines such as interleukin 1β (IL-1β), tumor necrosis factor (TNF), and also lipid mediators as leukotrienes. In addition, in diabetes, hyperglycemia and oxidative stress appear to accelerate the development of atherosclerosis, one mechanism could be via promotion of immune reactions. To prove that immune reactions are causative of atherosclerosis and CVD, further studies with immune-modulatory treatments are needed.

Pathogenic role of modified LDL antibodies and immune complexes in atherosclerosis

There is strong evidence supporting a key role of the adaptive immune response in atherosclerosis, given that both activated Th cells producing predominantly interferon-γ and oxidized LDL (oxLDL) and the corresponding antibodies have been isolated from atheromatous plaques. Studies carried out using immune complexes (IC) prepared with human LDL and rabbit antibodies have demonstrated proatherogenic and pro-inflammatory properties, mostly dependent on the engagement of Fcγ receptors Ⅰ and Ⅱ in macrophages and macrophage-like cell lines. Following the development of a methodology for isolating modified LDL (mLDL) antibodies from serum and isolated IC, it was confirmed that antibodies reacting with oxLDL and advanced glycation end product-modified LDL are predominantly IgG of subtypes 1 and 3 and that mLDL IC prepared with human reagents possesses pro-inflammatory and proatherogenic properties. In previous studies, LDL separated from isolated IC has been analyzed for its modifications, and the reactivity of antibodies isolated from the same IC with different LDL modifications has been tested. Recently, we obtained strong evidence suggesting that the effects of mLDL IC on phagocytic cells are modulated by the composition of the mLDL. Clinical studies have shown that the level of mLDL in circulating IC is a strong predictor of cardiovascular disease (CVD) and, in diabetic patients, other significant complications, such as nephropathy and retinopathy. In conclusion, there is convincing ex vivo and clinical data supporting the hypothesis that, in humans, the humoral immune response to mLDL is pathogenic rather than protective.

Passive immunization with hypochlorite-oxLDL specific antibodies reduces plaque volume in LDL receptor-deficient mice

Aims

New strategies to overcome complications of cardiovascular diseases are needed. Since it has been demonstrated that atherosclerosis is an inflammatory disease, modulation of the immune system may be a promising approach. Previously, it was suggested that antibodies may confer protective effects on the development of atherosclerosis. In this study, we hypothesised that passive immunization with anti-oxLDL IgM antibodies specific for hypochlorite (HOCl) may be athero-protective in mice.

Methods and Results

Monoclonal mouse IgM antibodies were produced and the antibody with specificity for hypochlorite-oxLDL (HOCl-oxLDL) (Moab A7S8) was selected. VH sequence determination revealed that Moab A7S8 is a natural IgM antibody. Atherosclerosis in LDLr^−/− mice was induced by a perivascular collar placement around the right carotid artery in combination with feeding a high-fat diet. Subsequently, the mice were treated every six days with 500 µg Moab A7S8, non-relevant IgM or with PBS and the carotid arteries and aortic roots were studied for atherosclerosis. Passive immunization with this Moab A7S8 resulted in a significant reduced plaque volume formation in LDLr^−/− mice when compared with PBS treatment (P = 0.002 and P = 0.035). Cholesterol levels decreased by 20% when mice were treated with Moab A7S8 compared to PBS. Furthermore, anti-oxLDL specific IgM and IgG antibody production increased significantly in the Moab A7S8 treated mice in comparison with PBS treated mice.

Conclusion

Our data show that passive immunization with a natural IgM antibody, directed to HOCl-oxLDL, can reduce atherosclerotic plaque development. We postulate that specific antibody therapy may be developed for use in human cardiovascular diseases.

Low levels of a natural IgM antibody are associated with vein graft stenosis and failure

BACKGROUND

All humans have natural, protective antibodies directed against phosphorylcholine (PC) epitopes, a common inflammatory danger signal appearing at sites of cell injury, oxidative stress, and on bacterial capsules. In large human cohorts, low levels of anti-PC IgM were associated with a significantly increased risk of stroke or myocardial infarction. However, it is not known if these antibodies protect against the premature closure of arterial reconstructions.

METHODS

A prospective, observational study of patients undergoing elective, infrainguinal, autogenous vein bypasses for atherosclerotic occlusive disease of the legs was conducted. Clinical data were recorded prospectively, and preoperative levels of anti-PC IgM measured with the CVDefine kit from Athera Biotechnologies (Solna, Sweden). The principal clinical end point was the loss of primary patency (loss of graft flow, or any intervention for stenosis). Patients were followed regularly by duplex ultrasound at 1, 3, 6, 12, 18 months, and yearly thereafter.

RESULTS

Fifty-six patients were studied, for an average of 1.3 years. Indications for surgery were claudication (33.9%), ischemic rest pain (17.9%), and ischemia with ulceration or gangrene (48.2%). Seventeen (30.4%) patients experienced loss of primary patency (10 graft occlusions, seven surgical or endovascular revisions of graft stenoses). Kaplan-Meier survival analysis showed that the quartile of patients with the lowest anti-PC IgM levels had significantly worse primary graft patency (log-rank test, P = .0085). Uni- and multivariate Cox proportional hazards analysis revealed that the preoperative anti-PC IgM level was an important predictor of graft failure. Patients with IgM values in the lowest quartile had a 3.6-fold increased risk of graft failure (95% confidence interval: 1.1-12.1), even after accounting for other significant clinical or technical factors such as indication for surgery, site of distal anastomosis, or vein graft diameter.

CONCLUSIONS

A naturally occurring IgM antibody directed against the proinflammatory epitope PC may be protective against vein graft stenosis and failure, through anti-inflammatory mechanisms. Measurement of this antibody may be a useful prognostic indicator, although larger studies of more diverse populations will be needed to confirm these results. The biological actions of anti-PC IgM suggest it may be useful in developing immunotherapies to improve bypass longevity.

Auto-antibodies as emergent prognostic markers and possible mediators of ischemic cardiovascular diseases

During the last 15 years, a growing body of evidence supported the fact that auto-antibodies represent not only emergent markers but also active mediators of cardiovascular disease (CVD), clinically represented mostly by acute coronary syndrome (ACS) and stroke. There is a contrasted relationship between auto-antibodies and CVD, some being protective, while others acting as potential risk factors. Therefore, we performed a review of the literature on the respective cardiovascular prognostic value of the most relevant auto-antibodies in ACS and stroke, and their putative pathophysiological properties in atherogenesis. This review highlights auto-antibodies as active modulators of the innate immune system in atherogenesis (either toward a pro- or anti-inflammatory response), or by affecting basal heart rate regulation (anti-apoA-1 IgG). Given their apparent prognostic independency towards traditional cardiovascular risk factors, the data available in the literature indicates that some of those auto-antibodies could be of valuable help for cardiovascular risk stratification in the future, especially because their deleterious effects have been shown to be potentially abrogated in vivo and in vitro by existing therapeutic modalities. Although evidence in humans is currently lacking, these studies may open innovative therapeutic perspectives for CVD in the future.

Immunoassay of modified forms of human low density lipoprotein in isolated circulating immune complexes

Modified lipoproteins are able to induce inflammatory reactions through innate immunity pathways and are immunogenic, leading to an autoimmune response that results in the formation of proinflammatory immune complexes. The measurement of circulating oxidized lipoproteins and corresponding antibodies has, therefore, been proposed as an approach to assess the risk for complications in patients with diabetes and for the risk of cardiovascular disease in the general population. However, the majority of modified low density lipoprotein (LDL) in the peripheral circulation exists in the form of immune complexes, and this is a significant obstacle for the measurement of modified LDL and the corresponding antibodies. In this manuscript, we describe in detail the methodology developed by our group for isolation and fractionation of circulating immune complexes (IC), allowing the accurate assay of different LDL modifications. This approach has resulted in several studies showing that the levels of modified LDL are risk factors with a stronger association to diabetic retinopathy, nephropathy, and macrovascular disease. Ongoing research is focused on evaluating the predictive power of modified LDL levels for the development or progression of atherosclerotic cardiovascular disease in other patient populations and on the simplification of the assay to make it more applicable to diagnostic laboratories.

Immunity, atherosclerosis and cardiovascular disease

Atherosclerosis, the major cause of cardiovascular disease (CVD), is a chronic inflammatory condition with immune competent cells in lesions producing mainly pro-inflammatory cytokines. Dead cells and oxidized forms of low density lipoproteins (oxLDL) are abundant. The major direct cause of CVD appears to be rupture of atherosclerotic plaques. oxLDL has proinflammatory and immune-stimulatory properties, causes cell death at higher concentrations and contains inflammatory phospholipids with phosphorylcholine (PC) as an interesting epitope. Antibodies against PC (anti-PC) may be atheroprotective, one mechanism being anti-inflammatory. Bacteria and virus have been discussed, but it has been difficult to find direct evidence, and antibiotic trials have not been successful. Heat shock proteins could be one major target for atherogenic immune reactions. More direct causes of plaque rupture include pro-inflammatory cytokines, chemokines, and lipid mediators. To prove that inflammation is a cause of atherosclerosis and CVD, clinical studies with anti-inflammatory and/or immune-modulatory treatment are needed. The potential causes of immune reactions and inflammation in atherosclerosis and how inflammation can be targeted therapeutically to provide novel treatments for CVD are reviewed.

Evidence on the pathogenic role of auto-antibodies in acute cardiovascular diseases

Atherothrombosis is the major determinant of acute ischaemic cardiovascular events, such as myocardial infarction and stroke. Inflammatory processes have been linked to all phases of atherogenesis In particular, the identification of autoimmunity mediators in the complex microenvironment of chronic inflammation has become the focus of attention in both early and advanced atherogenic processes. Auto-antibodies against self-molecules or new epitopes generated by oxidative processes infiltrate atherosclerotic plaques and were shown to modulate the activity of immune cells by binding various types of receptors. However, despite mounting evidence for a pathophysiological role of autoantibodies in atherothrombosis, the clinical relevance for circulating autoantibodies in cardiovascular outcomes is still debated. This review aims at illustrating the mechanisms by which different types of autoantibodies might either promote or repress atherothrombosis and to discuss the clinical studies assessing the role of auto-antibodies as prognostic biomarkers of plaque vulnerability.

Low levels of IgM antibodies to oxidized cardiolipin increase and high levels decrease risk of cardiovascular disease among 60-year olds: a prospective study

Background

Antibodies against cardiolipin (aCL) are associated with increased risk of cardiovascular disease (CVD). We here determine the role of antibodies against oxidized CL (aOxCL).

Methods

One third of sixty-year olds from the Stockholm County were screened (2039 men, 2193 women), where 211 incident CVD-cases and 633 age- and sex-matched controls were identified (5–7 year follow-up). Antibodies were determined by ELISA and uptake of oxLDL in macrophages by FACScan.

Results

IgM aOxCL was lower among CVD cases than controls (p=0.024). aOxCL-levels were divided in quartiles with the highest quartile set as the reference group. After adjustment for smoking, BMI, type II diabetes, hypercholesterolaemia and hypertension, an increased risk was determined in the lowest quartile of IgM aOxCL (OR: 1.80, CI: 1.12–2.91, p=0.0159); OR for men in the lowest quartile was 2.46 (CI 1.34–4.53, p=0.0037) for CVD and for stroke: 12.28 (CI: 1.48-101.77, p=0.02). IgG aOxCL levels did not differ between quartiles in CVD-risk. High levels of IgM aOxCL (reaching significance above 86th) and IgG aOxCL (above 95th percentile) were associated with decreased risk of CVD (OR: 0.485, CI: 0.283-0.829; p=0.0082 and OR: 0.23, CI: 0.07-0.69; p=0.0091). aCL were not associated with CVD. oxCL but not CL competed out uptake of OxLDL in macrophages, and aOxLDL recognized oxCL but not CL. In contrast to aCL, aOxCL was not dependent on co-factor Beta2-glycoprotein-I.

Conclusions

aOxCL is a novel risk/protection marker for CVD, with therapeutic implications. OxCL competes with oxLDL for uptake in macrophages and the possibility that aOxCL inhibits such uptake by interfering with same or similar epitopes in oxCL and oxLDL should be further studied.

Carotid atherosclerosis, disease measures, oxidized low-density lipoproteins, and atheroprotective natural antibodies for cardiovascular disease in early rheumatoid arthritis -- an inception cohort study

OBJECTIVE

Although an enhanced risk of cardiovascular disease (CVD) in persons with rheumatoid arthritis (RA) is well established, the mechanisms behind it remain unclear. We studied whether carotid atherosclerosis, RA disease measures, or potential cardiovascular biomarkers influenced the incidence of CVD in an RA inception cohort.

METHODS

RA disease measures and CVD biomarkers were assessed at 0, 3, 12, 24, and 60 months after disease onset, and carotid ultrasonography after 5 years. The study outcome was incident CVD events - acute myocardial infarction, angina pectoris, congestive heart failure, or ischemic cerebrovascular event. Survival analysis and Cox and longitudinal regressions were used for statistical analyses.

RESULTS

A total of 105 patients, without CVD events prior to RA onset, experienced 17 CVD events, an incidence rate of 1.35 events per 100 person-years (95% CI 0.71-2.0). The rate of CVD events did not differ with regard to measures of carotid intima-media thickness, but it was higher for patients with bilateral carotid plaques than for those without (p = 0.012). Improvement in Disease Activity Score for 28 joints, visual analog scale for pain, and Stanford Health Assessment Questionnaire score over the first year, as well as usage of methotrexate (MTX), was associated, independent of age, with reduction of risk of CVD event [hazard ratios 0.68 (95% CI 0.5-0.97), 0.97 (95% CI 0.95-0.99), 0.35 (95% CI 0.15-0.82), and 0.34 (95% CI 0.12-0.91), respectively]. In longitudinal analyses, increasing oxidized low-density lipoprotein (oxLDL) and probability for low antiphosphorylcholine antibodies (anti-PC) were observed in those who experienced a subsequent CVD event.

CONCLUSION

Bilateral carotid plaques were associated with poor CVD-free survival. Early reductions of inflammation, pain, and disability as well as MTX usage were associated with better CVD outcome. Elevated oxLDL and low IgM anti-PC levels may link chronic inflammation in RA to enhanced risk of CVD events.

IgM-phosphorylcholine autoantibodies and outcome in acute coronary syndromes

BACKGROUND

Antibodies against proinflammatory phosphorylcholine (anti-PC) seem to be protective and reduce morbidity. We sought to determine whether low levels of immunoglobulin-M (IgM) autoantibodies against PC add prognostic information in acute coronary syndromes (ACS).

METHODS

IgM anti-PC titers were measured in serum obtained within 24h of admission from 1185 ACS patients (median age 66 years, 30% women). We evaluated major acute cardiovascular events (MACE) and all-cause mortality short--(6 months), intermediate--(18 months) and long--(72 months) terms.

RESULTS

Low anti-PC titers were associated with MACE and all-cause mortality at all follow-up times. After adjusting for clinical variables, plasma troponin-I, proBNP and CRP levels, associations remained at all times with MACE, short and intermediate terms also with all-cause mortality. With anti-PC titers below median, adjusted hazard ratios at 18months were for MACE 1.79 (95% confidence interval [CI]: 1.31 to 2.44; p=0.0002) and for all-cause mortality 2.28 (95% CI: 1.32 to 3.92; p=0.003). Anti-PC and plasma CRP were unrelated and added to risk prediction.

CONCLUSIONS

Serum IgM anti-PC titers provide prognostic information above traditional risk factors in ACS. The ease of measurement and potential therapeutic perspective indicate that it may be a valuable novel biomarker in ACS.

Future potential biomarkers for postinterventional restenosis and accelerated atherosclerosis

New circulating and local arterial biomarkers may help the clinician with risk stratification or diagnostic assessment of patients and selecting the proper therapy for a patient. In addition, they may be used for follow-up and testing efficacy of therapy, which is not possible with current biomarkers. Processes leading to postinterventional restenosis and accelerated atherosclerosis are complex due to the many biological variables mediating the specific inflammatory and immunogenic responses involved. Adequate assessment of these processes requires different and more specific biomarkers. Postinterventional remodeling is associated with cell stress and tissue damage causing apoptosis, release of damage-associated molecular patterns and upregulation of specific cytokines/chemokines that could serve as suitable clinical biomarkers. Furthermore, plasma titers of pathophysiological process-related (auto)antibodies could aid in the identification of restenosis risk or lesion severity. This review provides an overview of a number of potential biomarkers selected on the basis of their role in the remodeling process.

IgM phosphorylcholine antibodies inhibit cell death and constitute a strong protection marker for atherosclerosis development, particularly in combination with other auto-antibodies against modified LDL

BACKGROUND

We have reported that anti-phosphorylcholine (anti-PC) IgM is a protection marker for human cardiovascular disease (CVD) and atherosclerosis. We here investigate the anti-PC autoantibodies in a well-defined cohort with regard to idiotype, atherosclerosis progression and mechanisms for its protective action.

METHODS

Serum levels and binding specificities of different anti-PC isotypes were determined in 226 hypertensive individuals enrolled in European Lacidipine Study on Atherosclerosis using ELISA. The mean of the maximum Intima-Media Thicknesses (IMT) in the far walls of common carotids and bifurcations was assessed at the time of inclusion, and four years afterwards. Apoptosis in immune cells was induced with lysophosphatidylcholine (LPC) and quantified using the MTT-assay.

RESULTS

Anti-PC IgM, IgA and IgG1 (but not IgG2) was negatively associated with IMT-progression. Combining anti-PC IgM with data on antibodies against oxidized- and malondialdehyde-modified LDL further strengthened this association. At very high levels, anti-PC IgM exhibited a striking negative association with atherosclerosis progression (OR 0.05; CI 0.006-0.40). Analysis of serum samples taken four years apart in study participants affirmed the stability of anti-PC IgM titers over time. Examination of fine specificities revealed that the protective isotypes (IgM, IgA and IgG1) are of the Group I idiotype whereas the non-protective IgG2 subclass was Group II. Anti-PC IgM inhibited LPC-induced cell death of immune cells.

CONCLUSION

Group I anti-PC antibodies, particularly of the IgM class, are independent protection markers for atherosclerosis progression. One potential mechanism of action is inhibition of LPC-induced cell cytotoxicity.

Naturally occurring IgM antibodies to oxidation-specific epitopes

Naturally occurring antibodies (NAbs) have specificity for both microbial and self antigens, which allows them to act in the first line defense against invading pathogens, as well as in tissue homeostasis by mediating the clearance of cellular debris. This latter recognition of self by NAbs was often thought to reflect the polyreactivity of low affinity antibodies. The finding that oxidation-specific epitopes are dominant targets of naturally occurring IgM antibodies shed light on this and provided novel insights into the understanding of the house keeping functions of NAbs. Oxidation-specific epitopes represent stress-induced or altered self structures that are generated as a consequence of lipidperoxidation during many physiological and pathological situations. Importantly, the same structures have been found in the membranes of dying cells. Only oxidized lipids and dying cells-but not native membrane lipids or viable cells-are recognized by this set of NAbs. Thus, oxidation-specific epitopes represent ideal marks that identify biological waste for its clearance and the neutralization of its pro-inflammatory properties. Furthermore, this binding property of NAbs has also important implications for various chronic inflammatory diseases, including atherosclerosis.

High levels of IgM against methylglyoxal-modified apolipoprotein B100 are associated with less coronary artery calcification in patients with type 2 diabetes

OBJECTIVE

  Advanced glycation end products (AGE) have been implicated in diabetic vascular complications through activation of pro-inflammatory genes. AGE-modified proteins are also targeted by the immune system resulting in the generation of AGE-specific autoantibodies, but the association of these immune responses with diabetic vasculopathy remains to be fully elucidated. The aim of this study was to determine whether antibodies against apolipoprotein B100 modified by methylglyoxal (MGO-apoB100) are associated with coronary atherosclerosis in patients with type 2 diabetes.

METHODS

  We measured antibodies against MGO-apoB100 in plasma from 497 type 2 diabetic patients without clinical signs of cardiovascular disease. Severity of coronary disease was assessed as coronary artery calcium (CAC) imaging. Immunoglobulin (Ig)M and IgG levels recognizing MGO-apoB100 were determined by enzyme-linked immunosorbent assay.

RESULTS

  Anti-MGO-apoB100 IgM antibody levels were higher in subjects with a low to moderate CAC score (≤400 Agatston units) than in subjects with a high score (>400 Agatston units; 136.8±4.4 vs. 101.6± 7.4 arbitrary units (AU), P<0.0001) and in subjects demonstrating no progression of CAC during 30 months of follow-up (136.4±5.7 vs. 113.9 ± 6.2 AU in subjects with progression, P<0.0001). Subjects with a family history of premature myocardial infarction had lower levels of anti-MGO-apoB100 IgM. Female subjects had higher levels of anti-MGO-apoB100 antibodies and lower CAC than men. Accordingly, high levels of IgM against MGO-apoB100 are associated with less severe and a lower risk of progression of coronary disease in subjects with type 2 diabetes.

CONCLUSIONS

Although conclusions regarding causal relationships based on epidemiological observations need to be made with caution, our findings suggest the possibility that anti-MGO-apoB100 IgM may be protective in diabetic vasculopathy.

Development of immunoassays for anti-electronegative LDL autoantibodies and immune complexes

BACKGROUND

Electronegative low-density lipoprotein (LDL-) promotes atherosclerosis through inflammatory and immunologic mechanisms that lead to the production of anti-LDL(-) autoantibodies and to the subsequent formation of immune complexes (IC) and macrophage foam cells. We described the development and validation of an ELISA for the quantification of free anti-LDL(-) autoantibodies and an ELISA for the quantification of IC consisting of LDL(-)-bound IgG in human plasma.

METHODS

LDL(-) purified from human plasma, and anti-LDL(-) monoclonal antibody Fab fragments were adsorbed onto ELISA plates to capture anti-LDL(-) autoantibodies and IC-LDL(-), respectively. The performance characteristics of both ELISAs, including the limits of detection and quantification, accuracy and inter- and intra-assay precision were evaluated. Linearity, interference and stability tests were also performed.

RESULTS

The calibration range of the anti-LDL(-) assay was 0.004-0.125 mU/l and plasma demonstrated a dilutional linearity when diluted 1:100, 1:200, 1:400 and 1:800. The calibration range of the IC-LDL(-) assay was 0.06-4 U/l, and plasma demonstrated a dilutional linearity when diluted 1:12.5, 1:25, 1:50 and 1:100. Both ELISAs showed intra- and inter-assay precision and recovery within the required limits for immunoassays.

CONCLUSION

These ELISAs can be used in clinical studies and for the biochemical investigation of atherosclerosis. In addition, they will enable the comprehensive evaluation of the importance of bound or free autoantibodies against LDL(-) in this disease.

IgM and its receptors: structural and functional aspects

This review combines the data obtained before the beginning of the 1990s with results published during the last two decades. The predominant form of the IgM molecule is a closed ring composed of five 7S subunits and a J chain. The new model of spatial structure of the pentamer postulates nonplanar mushroom-shaped form of the molecule with the plane formed by a radially-directed Fab regions and central protruding portion consisting of Cµ4 domains. Up to the year 2000 the only known Fc-receptor for IgM was pIgR. Interaction of IgM with pIgR results in secretory IgM formation, whose functions are poorly studied. The receptor designated as Fcα/µR is able to bind IgM and IgA. It is expressed on lymphocytes, follicular dendritic cells, and macrophages. A receptor binding IgM only named FcµR has also been described. It is expressed on T- and B-lymphocytes. The discovery of new Fc-receptors for IgM requires revision of notions that interactions between humoral reactions involving IgM and the cells of the immune system are mediated exclusively by complement receptors. In the whole organism, apart from IgM induced by immunization, natural antibodies (NA) are present and comprise in adults a considerable part of the circulating IgM. NA are polyreactive, germ-line-encoded, and emerge during embryogenesis without apparent antigenic stimuli. They demonstrate a broad spectrum of antibacterial activity and serve as first line of defense against microbial and viral infections. NA may be regarded as a transitional molecular form from invariable receptors of innate immunity to highly diverse receptors of adaptive immunity. By means of interaction with autoantigens, NA participate in maintenance of immunological tolerance and in clearance of dying cells. At the same time, NA may act as a pathogenic factor in atherosclerotic lesion formation and in development of tissue damage due to ischemia/reperfusion.

Gluten-free diet in nonceliac disease

A gluten-free diet (GFD) is commonly recognized as the treatment for celiac disease. It also has been investigated as a treatment option for other medical conditions, including dermatitis herpetiformis, irritable bowel syndrome, neurologic disorders, rheumatoid arthritis, diabetes mellitus, and HIV-associated enteropathy. The strength of the evidence for the use of a GFD in these nonceliac diseases varies, and future research may better define the benefits of a GFD for those conditions with weak existing evidence.

Patients with polycystic ovary syndrome have lower levels of IgM anti-phosphorylcholine antibodies than healthy women

INTRODUCTION

IgM antibodies against phosphorylcholine (IgM anti-PC) are natural autoantibodies, possibly exerting one of the atheroprotective functions of the immune system. Increased levels of these antibodies reduce the development of atherosclerosis in mice, and low levels of IgM anti-PC have been associated with increased risk for cardiovascular disease (CVD). This study compared levels of IgM anti-PC in women with polycystic ovary syndrome (PCOS, n = 111) and healthy controls (n = 79).

METHOD

Levels of IgM anti-PC were measured with ELISA.

RESULTS

The median level of IgM anti-PC in patients with PCOS was not significantly different compared to control subjects. However, the proportion of patients with PCOS with low levels of IgM anti-PC, defined as number of individuals below the median level, was significantly higher than among healthy controls, p < 0.05. Patients with PCOS in the oldest age quintile had significantly lower level of IgM anti-PC than control subjects of similar age (p < 0.05) and younger women with PCOS (p < 0.01).

CONCLUSION

Our results indicate that women with PCOS more frequently display below-median levels of IgM anti-PC than controls and older women with PCOS have lower median anti-PC levels. Further studies of how this finding translates into actual CVD risk in women with PCOS are needed.

Cardiovascular co-morbidity in patients with rheumatic diseases

During recent years atherosclerosis, the major cause of cardiovascular disease (CVD), has been recognised as a chronic inflammatory condition in which rupture of atherosclerotic lesions appears to play a major role. The risk of CVD is raised in many rheumatic diseases. This risk is high in systemic lupus erythematosus - as much as a 50-times increase among middle-aged women has been reported. Studies on CVD and atherosclerosis in rheumatic disease could thus provide interesting information about CVD and atherosclerosis in addition to being an important clinical problem. A combination of traditional and nontraditional risk factors accounts for the increased risk of CVD and atherosclerosis in rheumatic disease. One interesting possibility is that atherosclerotic lesions in rheumatic disease are more prone to rupture than normal atherosclerotic lesions. It is also likely that increased risk of thrombosis may play an important role, not least in systemic lupus erythematosus. Further, it is not clear whether an increased risk of CVD is a general feature of rheumatic disease, or whether this only occurs among subgroups of patients. It should be emphasised that there is an apparent lack of treatment studies where CVD in rheumatic disease is the end point. Control of disease activity and of traditional risk factors, however, appears to be well founded in relation to CVD in rheumatic disease. Further studies are needed to determine the exact role of lipid-lowering drugs as statins. Hopefully novel therapies can be developed that target the causes of the inflammation in atherosclerotic lesions both in rheumatic patients and in the general population.

Genetic and environmental regulation of inflammatory CVD biomarkers Lp-PLA2 and IgM anti-PC

OBJECTIVE

We set out to investigate the relative contribution of genetic and environmental effect on two inflammatory CVD biomarkers; lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) and anti-phosphorylcholine IgM (anti-PC). Their relationships and possible co-regulation with other established CVD biomarkers are also examined.

METHODS

Lp-PLA(2) activity (N=1600) and anti-PC (N=2036) levels were measured in elderly Swedish twins. Correlation analyses and heritability estimation were conducted by structural equation modeling.

RESULTS

We attribute 0.37 of the variance of Lp-PLA(2) and 0.40 of anti-PC variance to genetic variance. In addition, a bivariate heritability of 0.33, 0.35 and 0.36 could be detected for levels of Lp-PLA(2) together with ApoB, total cholesterol and LDL, respectively. Anti-PC was only weakly related to other biomarkers of CVD, which may suggest a more independent role of anti-PC as a biomarker.

CONCLUSIONS

In this large sample, Lp-PLA(2) activity has lower heritability and higher environmental regulation than previously reported. Anti-PC levels are partly influenced by dominance genetics and appear to be regulated independently of more established CVD biomarkers.

Dendritic cells, antibodies reactive with oxLDL, and inflammation

Periodontitis appears to promote chronic inflammatory diseases, including atherosclerosis, but relevant mechanisms need clarification. Oral bacteria induce antibodies that bind not only bacteria, but also oxLDL. Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans induce remarkable IgG responses that are dominated by IgG2, and IgG2 is IFN-γ-dependent and is promoted by dendritic cells (DCs). LDL-reactive antibodies induced by P. gingivalis and A. actinomycetemcomitans include anti-phosphorylcholine (α-PC) and β2-glycoprotein-1-dependent anticardiolipin (α-CL), and these antibodies may link chronic inflammatory diseases at a mechanistic level. Antibody-mediated uptake of oxLDL or bacteria dramatically enhances DC-IL-12, and DC-IL-12 induces NK-cell-IFN-γ responses that promote Th-1 responses and sustained inflammation. DCs may be derived from monocytes, and this is striking in cultures of aggressive periodontitis (AgP) monocytes, where DC numbers are about double control levels. Moreover, serum α-CL levels in individuals with AgP are frequently elevated, and these antibodies promote atherosclerosis in persons with antiphospholipid syndrome. Elevated serum levels of soluble-intercellular adhesion molecule, soluble-vascular cell adhesion molecule, and soluble-E-selectin are atherosclerosis-associated indicators of vascular inflammation, and these markers are elevated in the subset of AgP patients with high α-CL. We reason that periodontitis patients with elevated antibodies reactive with oxLDL could be a subgroup at high risk for cardiovascular sequelae.

Low level of physical activity in women with rheumatoid arthritis is associated with cardiovascular risk factors but not with body fat mass--a cross sectional study

BACKGROUND

As many patients with rheumatoid arthritis (RA) have increased fat mass (FM) and increased frequency of cardiovascular diseases we evaluated if total physical activity (MET-hours) had impact on body composition and cardiovascular risk factors in women with RA.

METHODS

Sixty-one out-ward RA women, 60.8 (57.3-64.4) years, answered a self-administered questionnaire, to estimate total daily physical activity during the previous year. Physical activity level was given as metabolic equivalents (MET) × h/day. Diet content was assessed by a food frequency questionnaire and body composition by whole-body dual-energy X-ray absorptiometry. Blood lipids and antibodies against phosphorylcholine (anti-PC) were determined.

RESULTS

Forty-one percent of the women had BMI > 25, 6% were centrally obese and 80% had FM% > 30%. The median (IQR) total physical activity was 40.0 (37.4-47.7), i.e. the same activity level as healthy Swedish women in the same age. Total physical activity did not significantly correlate with disease activity, BMI or FM%. Disease activity, BMI and FM% did not differ between those in the lowest quartile of total physical activity and those in the highest quartile. However, the women in the lowest quartile of physical activity had lower HDL (p = 0.05), Apo A1 (p = 0.005) and atheroprotective natural anti-PC (p = 0.016) and higher levels of insulin (p = 0.05) and higher frequency of insulin resistance than those in the highest quartile. Women in the lowest quartile consumed larger quantities of saturated fatty acids than those in the highest quartile (p = 0.042), which was associated with high oxidized low-density lipoprotein (oxLDL).

CONCLUSION

This cross sectional study demonstrated that RA women with fairly low disease activity, good functional capacity, high FM and high frequency of central obesity had the same total physical activity level as healthy Swedish women in the same age. The amount of total physical activity was not associated with functional capacity or body composition. However, low total physical activity was associated with dyslipidemia, insulin resistance, low levels of atheroprotective anti-PC and consumption of saturated fatty acids, which is of interest in the context of increased frequency of cardiovascular disease in RA.

Increased prevalence of vulnerable atherosclerotic plaques and low levels of natural IgM antibodies against phosphorylcholine in patients with systemic lupus erythematosus

INTRODUCTION

The risk of cardiovascular disease (CVD) and atherosclerosis is reported to be increased in systemic lupus erythematosus (SLE). We recently reported a negative association between natural IgM-antibodies against phosphorylcholine (anti-PC) in the general population, high anti-PC levels leading to decreased atherosclerosis development and low levels to increased risk of CVD. Potential mechanisms include anti-inflammatory properties and inhibition of uptake of oxidized low density lipoprotein (LDL) in macrophages. The objective herein was to study atherosclerosis in SLE in detail and in relation to traditional and non-traditional risk factors.

METHODS

A total of 114 patients with SLE were compared with 122 age- and sex-matched population-based controls. Common carotid intima-media thickness (IMT), calculated intima-media area (cIMa) and plaque occurrence were determined by B-mode ultrasound as a surrogate measure of atherosclerosis. Plaques were graded according to echogenicity and grouped as 1 to 4, with 1 being echoluscent, and considered most vulnerable. Anti-PC was studied by ELISA.

RESULTS

Hypertension, triglycerides and insulin resistance (determined by homeostasis model assessment of insulin resistance) and C-reactive protein (CRP) were increased in SLE (P < 0.01) while smoking, LDL, high density lipoprotein (HDL) did not differ between groups. Low levels of anti-PC IgM (lowest tertile) were more common in SLE patients than in controls (P = 0.0022). IMT and cIMa did not differ significantly between groups. However, plaques were more often found in SLE patients (P = 0.029). Age, LDL and IgM anti-PC (lowest tertile) were independently associated with plaque occurrence in SLE. Further, in the left carotid arteries echoluscent plaques (grade 1) were more prevalent in SLE as compared to controls (P < 0.016).

CONCLUSIONS

Plaque occurrence in the carotid arteries is increased in SLE and is independently associated with age, LDL and low anti-PC levels. Vulnerable plaques were more common in SLE. Anti-PC could be a novel risk marker also with a therapeutic potential in SLE.

Characterization of gene use and efficacy of mouse monoclonal antibodies to Streptococcus pneumoniae serotype 8

Streptococcus pneumoniae is the most common cause of community-acquired pneumonia in the United States and globally. Despite the availability of pneumococcal capsular polysaccharide (PPS) and protein conjugate-based vaccines, the prevalence of antibiotic-resistant pneumococcal strains, serotype (ST) replacement in nonconjugate vaccine strains, and uncertainty as to whether the PPS vaccine that is used in adults protects against pneumonia emphasize the need for continued efforts to understand the nature of protective PPS antibody responses. In this study, we generated mouse monoclonal antibodies (MAbs) to a conjugate consisting of the PPS of serotype 8 (PPS8) S. pneumoniae and tetanus toxoid. Thirteen MAbs, including four IgMs that bound to PPS8 and phosphorylcholine (PC) and five IgMs and four IgG1s that bound to PPS8 but not PC, were produced, and their nucleotide sequences, epitope and fine specificity, and efficacy against lethal challenge with ST8 S. pneumoniae were determined. MAbs that bound to PPS8 exhibited gene use that was distinct from that exhibited by MAbs that bound to PC. Only PPS8-binding MAbs that did not bind PC were protective in mice. All 13 MAbs used germ line variable-region heavy (V(H)) and light (V(L)) chain genes, with no evidence of somatic hypermutation. Our data reveal a relationship between PPS specificity and V(H) gene use and MAb efficacy in mice. These findings provide insight into the relationship between antibody molecular structure and function and hold promise for the development of novel surrogates for pneumococcal vaccine efficacy.