Identification of atherosclerosis-associated conformational heat shock protein 60 epitopes by phage display and structural alignment

Identification of heptapeptides targeting a lethal bacterial strain in septic mice through an integrative approach

Effectively killing pathogenic bacteria is key for the treatment of sepsis. Although various anti-infective drugs have been used for the treatment of sepsis, the therapeutic effect is largely limited by the lack of a specific bacterium-targeting delivery system. This study aimed to develop antibacterial peptides that specifically target pathogenic bacteria for the treatment of sepsis. The lethal bacterial strain Escherichia coli MSI001 was isolated from mice of a cecal ligation and puncture (CLP) model and was used as a target to screen bacterial binding heptapeptides through an integrative bioinformatics approach based on phage display technology and high-throughput sequencing (HTS). Heptapeptides binding to E. coli MSI001 with high affinity were acquired after normalization by the heptapeptide frequency of the library. A representative heptapeptide VTKLGSL (VTK) was selected for fusion with the antibacterial peptide LL-37 to construct the specific-targeting antibacterial peptide VTK-LL37. We found that, in comparison with LL37, VTK-LL37 showed prominent bacteriostatic activity and an inhibitive effect on biofilm formation in vitro. In vivo experiments demonstrated that VTK-LL37 significantly inhibited bacterial growth, reduced HMGB1 expression, alleviated lesions of vital organs and improved the survival of mice subjected to CLP modeling. Furthermore, membrane DEGP and DEGQ were identified as VTK-binding proteins by proteomic methods. This study provides a novel strategy for targeted pathogen killing, which is helpful for the treatment of sepsis in the era of precise medicine.

Effect of clopidogrel vs. aspirin on pro-atherosclerotic NLRP1 inflammasome expression in endothelial cells. ECLOAS study

INTRODUCTION AND OBJECTIVES

NRP1 inflammasome is crucial in endothelial dysfunction. Platelets are mandatory for the inflammation that precedes it. Aspirin could inhibit NLRP1 inflammasome in endothelial cells, and clopidogrel could also provoke a reduction in vascular inflammation. A study was carried out on the influence of platelet inflammatory inhibition by P2Y receptor inhibition versus COX enzyme inhibition on the transcription of NLRP1 inflammasome in endothelial cells.

METHODS

An open-label, prospective, randomised crossover study with two periods of platelet inhibition enrolled 20 healthy volunteers. They received clopidogrel 75mg/day/7days and aspirin 100mg/day/7days. A venous blood sample was collected from all participants before and after this period. Human aortic endothelial cells (HAECs) were exposed for 2h in cultures. NLRP1 gene expression was then analysed in these cultures.

RESULTS

HAEC cultures that were exposed to baseline plasma showed higher expression of NLRP1 than HAECs exposed to plasma after one week of aspirin or clopidogrel intake [relative quantification (RQ), 1.077±0.05 vs. 1.002±0.06; OR, 1.8; 95% CI, 1.1-2.9; P<.01 and 1.077±0.05 vs. 1.04±0.03; OR, 1.7; 95% CI, 1.2-2.6; P<.001, respectively]. NLRP1 expression in HAEC cultures exposed to plasma after one week of aspirin or clopidogrel was similar to that observed in control HAECs that was no exposed to human plasma (PBS) [RQ; 1.002±0.06 vs. 1.009±0.03; OR, 0.9; 95% CI, 0.5-1.4; P=.7, and 1.04±0.03 vs. 1.009±0.03; OR, 0.8; 95% CI, 0.3-1.2; P=.5, respectively]. No difference was observed in NLRP1 percentage reduction in HAEC after aspirin or clopidogrel exposure (3.8% vs. 2.8%, P=.3, respectively).

CONCLUSIONS

Platelet inhibition by P2Y pathway is similar to COX pathway in NLRP1 expression inhibition in HAECs.

Autoantibodies to a specific peptide epitope of human Hsp60 (ATVLA) with homology to Helicobacter pylori HspB in H. pylori-infected patients

Helicobacter pylori (Hp) may initiate autoimmunity as a result of molecular mimicry. The aim of this study was to compare the level of IgG antibodies to a specific epitope (P1 peptide) of human heat shock protein (Hsp)60 homologous to Hp Hsp60 (HspB) in the sera of healthy donors (HD), patients with Hp-related gastritis or coronary heart disease (CHD), uninfected or with Hp infection confirmed by rapid urease test, histological examination (dyspeptic patients) the ¹³ C urea breath test (¹³ C UBT), and anti-Hp antibodies (healthy donors, CHD patients). The Anti-P1 IgG induction by Hp was verified by adsorption of sera with these bacteria and by experimental immunization of Caviae porcellus with Hp. Cytokine secretion by THP-1Blue™ monocytes in response to P1 was also assessed. Anti-P1 antibodies were detected in patients with gastritis or CHD infected with Hp and they were not found in uninfected individuals or asymptomatic carriers. No antibodies were raised against P2 in any group. Reduced cross-reactivity to P1 was exhibited by sera adsorbed with Hp. Caviae porcellus infected with Hp produced anti-P1 autoantibodies. THP-1XBlue™ monocytes responded to P1 by production of proinflammatory cytokines. Autoantibodies against P1 in Hp-positive patients with gastritis or CHD and upregulation of proinflammatory cytokines by P1 may contribute to the pathogenesis of Hp infection.

CTHRSSVVC Peptide as a Possible Early Molecular Imaging Target for Atherosclerosis

The purpose of our work was to select phages displaying peptides capable of binding to vascular markers present in human atheroma, and validate their capacity to target the vascular markers in vitro and in low-density lipoprotein receptor knockout (LDLr(-/-)) mouse model of atherosclerosis. By peptide fingerprinting on human atherosclerotic tissues, we selected and isolated four different peptides sequences, which bind to atherosclerotic lesions and share significant similarity to known human proteins with prominent roles in atherosclerosis. The CTHRSSVVC-phage peptide displayed the strongest reactivity with human carotid atherosclerotic lesions (p < 0.05), when compared to tissues from normal carotid arteries. This peptide sequence shares similarity to a sequence present in the fifth scavenger receptor cysteine-rich (SRCR) domain of CD163, which appeared to bind to CD163, and subsequently, was internalized by macrophages. Moreover, the CTHRSSVVC-phage targets atherosclerotic lesions of a low-density lipoprotein receptor knockout (LDLr(-/-)) mouse model of atherosclerosis in vivo to High-Fat diet group versus Control group. Tetraazacyclododecane-1,4,7,10-tetraacetic acid-CTHRSSVVC peptide (DOTA-CTHRSSVVC) was synthesized and labeled with (111)InCl₃ in >95% yield as determined by high performance liquid chromatography (HPLC), to validate the binding of the peptide in atherosclerotic plaque specimens. The results supported our hypothesis that CTHRSSVVC peptide has a remarkable sequence for the development of theranostics approaches in the treatment of atherosclerosis and other diseases.

Effect of Simvastatin Treatment on "In Vitro" NLRP1 Inflammasome Expression in Peripheral Arterial Disease

BACKGROUND

Inflammatory stress stimuli in the plasma of patients with peripheral artery disease (PAD) are able to trigger the expression of NLRP1 inflammasome in human aortic endothelial cells (HAECs). Our objective was to elucidate the effect of simvastatin treatment on NLRP1 inflammasome expression in endothelial cells exposed to the plasma of PAD patients.

METHODS

The study included 81 patients with PAD, 24 of them treated with simvastatin (20 mg/day) and 57 without statin therapy. HAECs between passages 3 and 6 were stimulated for 2 hr using the plasma samples of the study participants. NLRP1 gene transcription of HAECs exposed to the plasma of PAD patients was quantificated.

RESULTS

HAECs exposed to the plasma of PAD patients with simvastatin therapy showed significantly higher expression of the NLRP1 gene compared with those exposed to the plasma of PAD patients without this treatment (relative quantitation [RQ] 1.12 ± 0.06 vs. 1.06 ± 0.07, P = 0.03). Furthermore, HAECs exposed to the plasma of patients with critical limb ischemia and treated with simvastatin responded with a higher NLRP1 expression than those exposed to the plasma of simvastatin-treated patients with claudication (RQ 1.1 ± 0.3 vs. 0.99 ± 0.14, P < 0.001).

CONCLUSION

Simvastatin intake in PAD patients increases in vitro reactivity of NLRP1 inflammasome gene expression in HAECs, especially in critical limb ischemia patients.

Increased levels of anti-heat-shock protein 60 (anti-Hsp60) indicate endothelial dysfunction, atherosclerosis and cardiovascular diseases in patients with mixed connective tissue disease

Heat-shock protein 60 (Hsp60) has been shown to provoke inflammation, and anti-Hsp60 may facilitate the development of atherosclerosis. In this study, we have investigated 30 patients with mixed connective tissue disease (MCTD) and assessed anti-Hsp60 and their relationship to cardiovascular diseases (CVD). Out of 30 patients with MCTD, 15 had CVDs. Anti-Hsp60 antibody was determined by enzyme-linked immunosorbent assay. Since endothelial dysfunction and accelerated atherosclerosis are characteristic to MCTD, a wide array of MCTD-, endothelial dysfunction- and CVD-associated parameters was investigated: serum lipid levels, paraoxonase activity (PON1), rich nuclear ribonucleoprotein U1 (anti-U1RNP), anti-endothelial cell antibodies, anti-cardiolipin and anti-β2-glycoprotein I antibody isotypes (anti-CL and anti-β2GPI), endothelin-1 (ET-1) levels, also intima-media thickness (IMT), a quantitative indicator of atherosclerosis. In MCTD, anti-Hsp60 antibody levels were significantly higher than in healthy individuals (p < 0.02). MCTD patients with CVD had significantly higher levels of anti-Hsp60 compared to MCTD without CVD (p = 0.001). Patients with MCTD had significantly lower high-density lipoprotein cholesterol (p = 0.02) and PON activity (p < 0.001), and significantly increased systolic (p < 0.0002) and diastolic (p < 0.001) blood pressure compared to healthy individuals. Anti-U1RNP levels (p < 0.002) and IMT were higher in patients compared to controls (p = 0.002). The CVD-positive MCTD patients had increased anti-Hsp60 (p < 0.0013), anti-CL IgG (p = 0.0005), ET-1 serum concentration (p < 0.05) and IMT levels (p < 0.001) compared to MCTD patients without CVD. Anti-Hsp60 showed a strong correlation with anti-oxLDL (r = 0.36, p = 0.01) and serum ET-1 (r = 0.62, p < 0.001) and negative correlation with PON activity (r = -0.47, p = 0.01). Anti-Hsp60 indicates endothelial injury, CVD, and can function as a novel atherosclerotic risk factor, also a valuable diagnostic marker in patients with MCTD.

Attenuation of early atherosclerotic lesions by immunotolerance with β2 glycoprotein I and the immunomodulatory effectors interleukin 2 and 10 in a murine model

OBJECTIVE

This study assessed the effect of cellular and humoral autoimmune response inhibition after immunization with β2-glycoprotein I (β2-GPI) and the effect of immunomodulation with interleukin (IL)-2 and IL-10 in the development of early atherosclerotic vascular lesion in a murine model. Atherosclerosis is increasingly considered a chronic inflammatory disease with pathogenic autoimmune processes. Regulatory T cells, and their cytokines, have been implicated in the inhibition of the development of atherosclerotic lesions and involved in the immunologic tolerance induction.

METHODS

Eight-week-old male C57BL6 LDL-receptor deficient (LDLR(-/-)) mice were fed a cholesterol-rich (2.8%), high-saturated-fat (82%) diet for a week and divided in five groups. The groups received the following intravenous immunizations: group I (control group): one dose of 5 μg β2-GPI; group II: 5 μg β2-GPI I and 1 μg IL-2; group III: 5 μg β2-GPI and 0.75 μg of IL-10; and group IV: 5 μg β2-GPI, 1 μg IL-2, and 0.75 μg IL-10. The aortas of the mice were assessed 8 weeks after inoculation to determine the aortic lesion size and composition in all groups.

RESULTS

β2-GPI immunization attenuated the early atherosclerotic lesions development compared with the control group (P = .001). Macroscopic and histologic aortic atherosclerotic lesions were significantly decreased in the IL-2 and IL-10-treated groups in β2-GPI-tolerant mice compared with the β2-GPI-tolerant group without cytokine injection (P = .001). The association of both cytokines did not provoke a major inhibition in the atherosclerosis development when compared with groups injected with the two cytokines separately.

CONCLUSIONS

The immunotolerance induction against β2-GPI attenuates the development of atherosclerosis lesions in an animal model, enhanced by downregulation of the cellular and humoral autoimmune response provoked by IL-2 and IL-10.

The role of heat shock proteins in atherosclerosis

Atherosclerosis is a chronic, multifactorial disease that starts in youth, manifests clinically later in life, and can lead to myocardial infarction, stroke, claudication, and death. Although inflammatory processes have long been known to be involved in atherogenesis, interest in this subject has grown in the past 30-40 years. Animal experiments and human analyses of early atherosclerotic lesions have shown that the first pathogenic event in atherogenesis is the intimal infiltration of T cells at arterial branching points. These T cells recognize heat shock protein (HSP)60, which is expressed together with adhesion molecules by endothelial cells in response to classic risk factors for atherosclerosis. Although these HSP60-reactive T cells initiate atherosclerosis, antibodies to HSP60 accelerate and perpetuate the disease. All healthy humans develop cellular and humoral immunity against microbial HSP60 by infection or vaccination. Given that prokaryotic (bacterial) and eukaryotic (for instance, human) HSP60 display substantial sequence homology, atherosclerosis might be the price we pay for this protective immunity, if risk factors stress the vascular endothelial cells beyond physiological conditions.

Hsp60 chaperonopathies and chaperonotherapy: targets and agents

INTRODUCTION

Hsp60 (Cpn60) assembles into a tetradecamer that interacts with the co-chaperonin Hsp10 (Cpn10) to assist client polypeptides to fold, but it also has other roles, including participation in pathogenic mechanisms.

AREA COVERED

Hsp60 chaperonopathies are pathological conditions, inherited or acquired, in which the chaperone plays a determinant etiologic-pathogenic role. These diseases justify selection of Hsp60 as a target for developing agents that interfere with its pathogenic effects. We provide information on how to proceed.

EXPERT OPINION

The information available encourages the development of ways to improve Hsp60 activity (positive chaperonotherapy) when deficient or to block it (negative chaperonotherapy) when pathogenic. Many questions are still unanswered and obstacles are obvious. More information is needed to establish when and why autologous Hsp60 becomes a pathogenic autoantigen, or induces cytokine formation and inflammation, or favors carcinogenesis. Clarification of these points will take considerable time. However, analysis of the Hsp60 molecule and a search for active compounds aimed at structural sites that will affect its functioning should continue without interruption. No doubt that some of these compounds will offer therapeutic hopes and will also be instrumental for dissecting structure-function relationships at the biochemical and biological (using animal models and cultured cells) levels.

Epitopes of microbial and human heat shock protein 60 and their recognition in myalgic encephalomyelitis

Myalgic encephalomyelitis (ME, also called Chronic Fatigue Syndrome), a common disease with chronic fatigability, cognitive dysfunction and myalgia of unknown etiology, often starts with an infection. The chaperonin human heat shock protein 60 (HSP60) occurs in mitochondria and in bacteria, is highly conserved, antigenic and a major autoantigen. The anti-HSP60 humoral (IgG and IgM) immune response was studied in 69 ME patients and 76 blood donors (BD) (the Training set) with recombinant human and E coli HSP60, and 136 30-mer overlapping and targeted peptides from HSP60 of humans, Chlamydia, Mycoplasma and 26 other species in a multiplex suspension array. Peptides from HSP60 helix I had a chaperonin-like activity, but these and other HSP60 peptides also bound IgG and IgM with an ME preference, theoretically indicating a competition between HSP60 function and antibody binding. A HSP60-based panel of 25 antigens was selected. When evaluated with 61 other ME and 399 non-ME samples (331 BD, 20 Multiple Sclerosis and 48 Systemic Lupus Erythematosus patients), a peptide from Chlamydia pneumoniae HSP60 detected IgM in 15 of 61 (24%) of ME, and in 1 of 399 non-ME at a high cutoff (p<0.0001). IgM to specific cross-reactive epitopes of human and microbial HSP60 occurs in a subset of ME, compatible with infection-induced autoimmunity.

Circulating anti-beta2-glycoprotein I antibodies are associated with endothelial dysfunction, inflammation, and high nitrite plasma levels in patients with intermittent claudication

Our aim is to investigate a possible association of circulating anti-beta2-glycoprotein I antibodies (ABGPI) with the endothelial dysfunction, nitric oxide bioactivity dysregulation, and the inflammatory status that surrounds peripheral arterial disease. We carried out an observational translational study, including 50 male patients with intermittent claudication and a healthy control group of 10 male subjects, age and sex matched with the cases. Flow-mediated arterial dilatation (FMAD) was assessed as a surrogate of endothelial dysfunction, and C-reactive protein (hsCRP) was determined as a marker of inflammation. Nitrite plasma levels were measured by colorimetric analysis. Circulating ABGPI titer was detected with indirect immunofluorescence. Titers <1 : 10 represented the reference range and the lower detection limit of the test. Circulating ABGPI titer ≥1 : 10 was detected in 21 (42%) patients and in none of the control subjects (P < 0.01). Patients with ABGPI titer ≥1 : 10 had a lower FMAD (P = 0.01). The CRP levels were higher in patients with ABGPI titer ≥1 : 10 (P = 0.04). The nitrite plasma levels were higher in patients with ABGPI titer ≥1 : 10 (P < 0.01). These data suggest that these circulating ABGPI may collaborate in the development of atherosclerosis; however, further prospective studies are required to establish a causal relationship.

Non-Fas(CD95/APO1)-mediated apoptosis of activated T cells inhibits the development of atherosclerosis

Atherosclerosis is a chronic systemic inflammatory disease. The innate and adaptive immune response might be involved in atherogenesis. Methotrexate (MTX) induces apoptosis of activated T cells by a CD95-independent pathway. The aim of this study was to analyse the effect of immunomodulation by MTX in the development of early atherosclerotic vascular lesions in an animal model. Four-week old male C57BL6 LDL-receptor-deficient mice were fed a diet rich in saturated fat (82%) and cholesterol (2.8%). Thirty animals were given a weekly intramuscular injection of MTX, establishing three subgroups: 10, 30 and 50 mg/kg. Ten further mice were used as an immunocompetent control group. Aortic thickening was significantly inhibited in all MTX-treated groups compared with the control group at 30 days (0.46 ± 0.003 mm(2) in the control group vs 0.31 ± 0.002, 0.14 ± 0.009 and 0.16 ± 0.006 mm(2) in the low-, intermediate- and high-dose group, respectively; P = 0.01) and at 60 days. The aortic lumen/total area ratio was also increased in the MTX-treated groups (0.82 ± 0.06 in the control group vs 0.88 ± 0.07, 0.86 ± 0.05 and 0.88 ± 0.04, respectively; P = 0.02). Immunosuppression by MTX inhibits the development of atherosclerotic lesions in arterial vessels in mice, which highlights the crucial role of the immune system in atherogenesis.

Peptide mimotopes of malondialdehyde epitopes for clinical applications in cardiovascular disease

Autoantibodies specific for malondialdehyde-modified LDL (MDA-LDL) represent potential biomarkers to predict cardiovascular risk. However, MDA-LDL is a high variability antigen with limited reproducibility. To identify peptide mimotopes of MDA-LDL, phage display libraries were screened with the MDA-LDL-specific IgM monoclonal Ab LRO4, and the specificity and antigenic properties of MDA mimotopes were assessed in vitro and in vivo. We identified one 12-mer linear (P1) and one 7-mer cyclic (P2) peptide carrying a consensus sequence, which bound specifically to murine and human anti-MDA monoclonal Abs. Furthermore, MDA mimotopes were found to mimic MDA epitopes on the surface of apoptotic cells. Immunization of mice with P2 resulted in the induction of MDA-LDL-specific Abs, which strongly immunostained human atherosclerotic lesions. We detected IgG and IgM autoAbs to both MDA mimotopes in sera of healthy subjects and patients with myocardial infarction and stable angina pectoris undergoing percutaneous coronary intervention, and the titers of autoAbs correlated significantly with respective Ab titers against MDA-LDL. In conclusion, we identified specific peptides that are immunological mimotopes of MDA. These mimotopes can serve as standardized and reproducible antigens that will be useful for diagnostic and therapeutic applications in cardiovascular disease.

Comparison of epitope specificity of anti-heat shock protein 60/65 IgG type antibodies in the sera of healthy subjects, patients with coronary heart disease and inflammatory bowel disease

Previously, we reported on the presence of antibodies to linear epitopes of human and mycobacterial 60 kD heat shock proteins (HSP) in the sera of healthy blood donors. Since many recent findings indicate that the levels of these antibodies may be altered in coronary heart disease (CHD) and also inflammatory bowel diseases (IBD), it seemed worthwhile to compare the epitope specificity of the anti-HSP60 and anti-HSP65 antibodies in the sera of patients with these diseases to those in healthy subjects. The multipin enzyme-linked immunosorbent assay method was applied with a large overlapping set of synthetic 10-mer peptides covering selected regions of human HSP60 and Mycobacterium bovis HSP65. Sera of 12 healthy persons (HP), 14 CHD, and 14 IBD patients with the same concentration of total anti-HSP60 and HSP65 IgG antibodies were tested. We have identified CHD-specific epitopes in the equatorial domain of the HSP60 protein but in neither region of the HSP65 molecule, indicating that the formation of anti-HSP60 antibodies is not or only partially due to the cross-reaction between human HSP60 and bacterial HSP65. IBD-specific epitopes were found in many regions of the HSP60 and in even more regions of the HSP65 molecule including an IBD-specific T cell epitope in region X as well. These findings indicate that the epitope specificity of the anti-human and anti-mycobacterial HSP60 antibodies associated with various diseases is different.

Heat shock protein 60 and immune inflammatory responses in atherosclerosis

Hallmarks of inflammation in various cardiovascular diseases, notably atherosclerosis, have been observed for a long time. However, evidence for an (auto)antigen-driven process at these sites of inflammation has come forward only recently. Heat shock proteins (HSPs) have been identified as playing either immunologically mediated disease promoting or protective roles. HSP60 has been shown to trigger innate and adaptive immune responses that initiate the earliest still reversible inflammatory stage of atherosclerosis. HSP60 is structurally highly conserved and abundantly expressed by prokaryotic and eukaryotic cells under stressful conditions. Beneficial protective immunity to microbial HSP60 acquired by infection or vaccination and bona fide autoimmunity to biochemically altered autologous HSP60 is present in all humans. In vitro and in vivo experiments have demonstrated that classical atherosclerosis risk factors can act as endothelial stressors that provoke the simultaneous expression of adhesion molecules and of HSP60 in mitochondria, in cytoplasm, and on the cell surface, where it acts as a "danger signal" for cellular and humoral immune reactions. Hence, protective, preexisting anti-HSP60 immunity may have to be "paid for" by harmful (auto)immune cross-reactive attack on arterial endothelial cells maltreated by atherosclerosis risk factors. These experimentally and clinically proven findings are the basis for the autoimmune concept of atherosclerosis.

Serum heat shock protein 60 can predict remission of flare-up in juvenile idiopathic arthritis

Heat shock protein (Hsp) 60 has been implicated in the pathogenesis of various inflammatory and autoimmune diseases. This study aimed to investigate synovial fluid and serum concentrations of Hsp60 and anti-Hsp60 and their relationship with juvenile idiopathic arthritis (JIA). Forty-eight patients with JIA, including 22 oligo-articular, 19 poly-articular, and 7 systemic diseases, and 33 normal controls were enrolled in this study. Synovial fluid and serum Hsp60 and anti-Hsp60 concentrations were measured via ELISA. Serum concentrations of Hsp60 of active and inactive oligo- and poly-articular JIA were significantly higher than those of normal controls. Serum concentration of anti-Hsp60 in active oligo-articular JIA was higher than that of normal controls (49.25 vs. 35.76 ng/mL, p = 0.059). Similarly, serum concentration of anti-Hsp60 in active poly-articular JIA was significantly higher than that of inactive samples (65.05 vs. 26.54 ng/mL, p = 0.008). In addition, serum concentration of Hsp60 correlated with the time required for remission from flare-ups in patients with JIA. Serum concentration of Hsp60 correlated well with time required for remission from flare-ups in patients with JIA, representing a potential disease marker to monitor disease activity.

Bioinformatics resources and tools for phage display

Databases and computational tools for mimotopes have been an important part of phage display study. Five special databases and eighteen algorithms, programs and web servers and their applications are reviewed in this paper. Although these bioinformatics resources have been widely used to exclude target-unrelated peptides, characterize small molecules-protein interactions and map protein-protein interactions, a lot of problems are still waiting to be solved. With the improvement of these tools, they are expected to serve the phage display community better.

Evidence for a novel human-specific xeno-auto-antibody response against vascular endothelium

Humans are genetically unable to synthesize the common mammalian sialic acid N-glycolylneuraminic acid (Neu5Gc). However, Neu5Gc can be metabolically incorporated and covalently expressed on cultured human cell surfaces. Meanwhile, humans express varying and sometimes high titers of polyclonal anti-Neu5Gc antibodies. Here, a survey of human tissues by immunohistochemistry with both a monospecific chicken anti-Neu5Gc antibody and with affinity-purified human anti-Neu5Gc antibodies demonstrates endothelial expression of Neu5Gc, likely originating from Neu5Gc-rich foods like red meats. We hypothesized that the combination of Neu5Gc incorporation and anti-Neu5Gc antibodies can induce endothelial activation. Indeed, the incubation of high-titer human sera with Neu5Gc-fed endothelial cells led to Neu5Gc-dependent antibody binding, complement deposition, endothelial activation, selectin expression, increased cytokine secretion, and monocyte binding. The proinflammatory cytokine tumor necrosis factor-alpha also selectively enhanced human anti-Neu5Gc antibody reactivity. Anti-Neu5Gc antibodies affinity-purified from human serum also directed Neu5Gc-dependent complement deposition onto cultured endothelial cells. These data indicate a novel human-specific mechanism in which Neu5Gc-rich foods deliver immunogenic Neu5Gc to the endothelium, giving anti-Neu5Gc antibody- and complement-dependent activation, and potentially contributing to human vascular pathologies. In the case of atherosclerosis, Neu5Gc is present both in endothelium overlying plaques and in subendothelial regions, providing multiple pathways for accelerating inflammation in this disease.

Antigen-driven evolution of B lymphocytes in coronary atherosclerotic plaques

Recent data indicated that adaptive immunity is involved in the process of atherogenesis. Oligoclonal recruitment of T lymphocytes has been described in coronary plaques of patients with acute coronary syndrome. However, the nature of immune response remains to be determined. In the present study, we examined the Ab response in six coronary plaques obtained by endoluminal directional atherectomy. The IgG1/kappa-coding gene repertoires of B lymphocytes present in circulating blood and in coronary plaques were cloned and analyzed. In all of the six plaques, we observed 1) a skewed usage of heavy and light IgG1/kappa Ab-coding genes, 2) an oligoclonal distribution of V(K), J(K), and V(H), D(H), and J(H) genes with overrepresentation of some rarely used IgG genes, and 3) the unequivocal signs of Ag-driven clonal expansion and evolution of B cells. The data document for the first time the presence of a local Ag-driven clonal evolution of B cells in human atherosclerotic plaques.

In vivo imaging of the effect of LPS on arterial endothelial cells: molecular imaging of heat shock protein 60 expression

Bacterial endotoxins are known as stress factors for endothelial cells. In 20 normocholesterolemic New Zealand White (NZW) rabbits, endothelial stress was induced by intravenous (i.v.) injection of lipopolysaccharide (LPS), while eight NZW rabbits were sham-treated or served as untreated controls. In vivo molecular imaging was performed using co-registered computer tomography and positron emission tomography 24 h after i.v. injection of (124)I-labeled monoclonal anti-HSP60 or (124)I-radiolabelled isotype control antibodies. Compared to control animals, in vivo images of rabbit aortae revealed significantly increased endothelial binding of (124)I-labeled anti-HSP60 antibodies upon LPS, especially at sites of aortal branching. This was confirmed by immunohistochemistry and autoradiography data. Our results showed, as proof-of-principle, that HSP60-expression in normocholesterolemic rabbits is significantly increased after induction of endothelial stress and that non-invasive in vivo molecular imaging of early aortal HSP60-expression using (124)I-labeled anti-HSP60 monoclonal antibodies is possible.

The autoimmune origin of atherosclerosis

Atherosclerosis is a chronic inflammatory disease. Many studies and observations suggest that it could be caused by an immune reaction against autoantigens at the endothelial level, the most relevant of which are oxidized LDL and heat shock proteins (HSP) 60/65. Endothelial dysfunction plays a fundamental role. The first antigen is related to the increased leakage and oxidation of LDL; the second to cellular reaction to stress. Experimental and clinical observations confirm the pathogenetic role of these antigens. Both innate and adaptive immunity and impaired regulatory mechanisms of the autoimmune reaction are involved. Different triggering factors are examined: infectious agents, smoking, air pollution, diabetes and hypercholesterolemia. Analogies and differences between systemic atherosclerosis and transplant-related coronary atherosclerosis help to understand their respective nature. Immune mechanisms might be responsible for the passage from stable plaque to unstable and rupture-prone plaque. Finally, prospects of treatment and prevention are linked to the induction of tolerance to responsible antigens, activation of immune regulatory response and the use of immunomodulatory drugs.

Antibodies against heat shock protein 60 derived from Helicobacter pylori: diagnostic implications in cardiovascular disease

Immune responses against heat shock protein 60 (HSP60) of pathogen-origin are thought to be defensive events which, due to molecular mimicry, misdirect to a human counterpart. Therefore, atherosclerosis may be serologically predicted by anti-HSP60 antibodies (Abs). In the present study, we analyzed the clinical prevalence of the serum IgG Abs against Helicobacter pylori (Hp)-derived HSP60 (Hp-HSP60) or its peptide fragments in patients with cardiovascular disease (CVD; n=250), as compared to those in age- and gender-matched non-CVD patients (n=293). Anti-Hp cell lysate Abs frequently appeared in Hp-infected patients who were not associated with CVD. In contrast, Abs against the particular amino acid sequence Hp-HSP60(II3) (II3 region, Glu(141)-Leu(160), in Hp-HSP60) predominantly appeared in CVD patients, as well as IgG anti-human HSP60 (Hu-HSP60(w)). Furthermore, neither titer of anti-Hp-HSP60(II3) nor anti-Hu-HSP60(w) Abs was correlated with the levels of high sensitivity C-reactive protein (hsCRP). This data strongly suggested that IgG anti-Hp-HSP60(II3) Abs cross-reacted with Hu-HSP60(w) were independent diagnostic markers relevant to CVD. Further, the 20 amino acid residues (Glu(141)-Leu(160)) might be predominant CVD-associated epitopes that induce anti-Hu-HSP60 auto-Abs, whose location was predicted in the tertiary structure of Hu-HSP60.