Identification of target antigens of antiendothelial cell antibodies in healthy individuals: A proteomic approach

Anti-fibroblast and anti-endothelial cell autoantibodies in pulmonary arterial hypertension (PAH) in patients with connective tissue diseases (CTD)

OBJECTIVES

Pulmonary arterial hypertension (PAH) is a rare disease that may be associated with CTD. Anti-fibroblast (AFA) and AECA have been identified in idiopathic and SSc-associated PAH. The aim was to identify autoantibodies discriminating for PAH associated with SLE, MCTD and primary SS, and their target antigens.

METHODS

Sera were collected in the French multicentre auto-HTAP study from 86 patients with CTD excluding SSc, including 32 with PAH (PAH+) and 54 without (PAH-). AFA and AECA were identified using one- (1D) and two-dimensional (2D) immunoblots and proteomics. ELISA tests using human recombinant proteins were used to confirm PAH-associated IgG reactivities.

RESULTS

PAH+ patients had similar IgG AFA and AECA reactivities in 56.2% and 40.6% of the cases in 1D immunoblots, respectively. In 2D immunoblots, serum IgG pools from SLE patients (n = 14), MCTD (n = 10), SS (n = 9) and 14 healthy controls (n = 1) recognized, respectively, 273 ± 79, 205 ± 77, 109 ± 11 and 109 protein spots in fibroblasts and 189 ± 48, 146 ± 30, 88 ± 33 and 190 protein spots in endothelial cell extracts. Serum IgG from PAH+ patients recognized 39 fibroblast and 34 endothelial cell protein spots that were not recognized by IgG from PAH- patients, including Annexin A5 (ANXA5). Anti-ANXA5 IgG reactivity was significantly higher in PAH+ compared with PAH- patients with MCTD (73% vs 0%, P < 0.001) and SLE (33% vs 0%, P = 0.009).

CONCLUSION

Anti-ANXA5 IgG autoantibody reactivity might represent a predictive biomarker for PAH associated with MCTD and SLE.

Clinical correlates of a subset of anti-fibroblast antibodies in systemic sclerosis

Anti-fibroblast antibodies (AFA) have been reported in systemic sclerosis (SSc) and are known to promote fibroblast activation. Aim of this study was to characterize the fine specificity of AFA and to analyze any correlations with clinical parameters associated to fibrosis. To this end, AFA were affinity-purified from a patient with diffuse cutaneous SSc (dcSSc) and interstitial lung disease (ILD). Panning of a phage display peptide library with purified AFA identified the motif . The peptide p121, bearing the AFA-specific motif, was used in ELISA to screen sera from 186 SSc patients and 81 healthy donors. Anti-p121 Ab serum levels were statistically higher in SSc than in healthy groups, and directly associated with dcSSc, reduced FVC (FVC < 70), and ILD. Given these clinical correlates, this study lays the groundwork for the identification of the antigen recognized by anti-p121 Ab, which might represent a novel therapeutic target for ILD.

Analysis of the Repertoires of Circulating Autoantibodies' Specificities as a Tool for Identification of the Tumor-Associated Antigens: Current Problems and Solutions

Circulating autoantibodies against tumor-associated autoantigens (TAA) may serve as valuable biomarkers for a wide range of diagnostic purposes. Modern immunology offers a large variety of methods for in-depth comparative analysis of the repertoires of circulating antibodies' antigenic specificities in health and disease. Nevertheless, this research field so far has met somewhat limited clinical success, while numerous data on the repertoires of circulating autoantibodies' specificities in cancer patients are poorly integrated into the contemporary picture of the immunological and molecular landscapes of human tumors. This review is an attempt to identify and systematize the key and essentially universal conceptual and methodological limitations of analyses of the repertoires of circulating antibodies' antigenic specificities in cancer (expression bias, redundancy of TAA repertoires, identification of natural IgG, the absence of the pathogenetically relevant context in the experimental systems used to detect TAA), as well as to discuss potential and already known methodological improvements that may significantly increase the detectability of the pathogenetically relevant and diagnostically significant bona fide TAA.

Autoimmune biomarkers in porto-sinusoidal vascular disease: Potential role in its diagnosis and pathophysiology

BACKGROUND AND AIMS

Porto-sinusoidal vascular disease (PSVD) is a rare disease that requires excluding cirrhosis and other causes of portal hypertension for its diagnosis because it lacks a specific diagnostical test. Although it has been occasionally associated with autoimmune diseases, the pathophysiology of PSVD remains unknown. The aim of this study was to evaluate the potential role of autoimmunity in the pathophysiology and diagnosis of PSVD.

METHODS

Thirty-seven consecutive patients with PSVD and 39 with cirrhosis matched by gender, signs of portal hypertension and liver function were included (training set). By using Indirect Immunofluorescence, ELISA and slot-blot methods data 22 autoantibodies were identified in patients with PSVD and cirrhosis. Presence of anti-endothelial cells antibodies (AECA) was assayed by a cell-based ELISA. Thirty-one PSVD, 40 cirrhosis patients, 15 patients with splenomegaly associated with haematological disease and 14 healthy donors were included in a validation set.

FINDINGS

The proportion of patients with at least one positive antibody was statistically significantly higher in patients with PSVD compared with cirrhosis (92% vs 56%; P < .01). Specifically, AECA were significantly more frequent in PSVD than in cirrhosis (38% vs 15%; P = .013). Results were confirmed in the validation set. In the overall population, presence of AECA had a 63% positive predictive value for diagnosing PSVD and a 71% negative predictive value, with a specificity of 94% when the 1/16 level is used as cut-off. AECA positive serum samples react with a 68-72 kDa protein of human liver endothelial sinusoidal cells.

Autoimmune vertigo: an update on vestibular disorders associated with autoimmune mechanisms

The role of the immune system in mediating cochleovestibular pathologies has received increasing attention in recent years. Autoimmune vertigo may be an invalidating condition and may worsen the quality of life of affected patients, especially in the cases of delayed diagnosis. Since the etiopathogenesis is still not clear, also the treatment is not yet completely delineated. According to the clinical presentation, autoimmune vertigo can present as an isolated disorder or in association with systemic autoimmune diseases. The main feature in autoimmune vertigo is the presence of an abnormal immune response, in either absence or presence of systemic autoimmune disease, directed against delicate components of the inner ear. This may determine a functional or anatomical alteration, with an inflammatory reaction often devastating for hearing and balance. Being the exact pathogenesis unknown, the diagnosis of autoimmune vertigo is based either on clinical criteria or on a positive response to steroids. The earlier the diagnosis is made, the sooner the therapy can be installed, giving a chance to the recovery of inner ear damages. Corticosteroids represent the most effective and universally accepted treatment, even if other immunomodulatory drugs are now having a more extensive use. HIGHLIGHTS: Vertigo is relatively frequent in autoimmune diseases; however, it is often misdiagnosed or attributed to central nervous system alterations rather to specific inner ear involvement. Vertigo and other audiovestibular symptoms may be the first manifestation of an autoimmune disease and if correctly addressed could significantly contribute to early diagnosis of the underlying autoimmune disease. Early diagnosis of immune-related vertigo can lead to prompt initiation of targeted therapy with elevate chances of preventing irreversible damages to the inner ear. The presence of alternating phases of well-being and disabling symptoms in patients with vertigo should always been considered, as they could suggest an underlying autoimmune condition.

Takayasu arteritis - epidemiology, pathogenesis, diagnosis and treatment

Takayasu disease belongs to the group of autoimmune vasculitis which most often affects the aorta and its branches. It is rare, and it mainly affects young women. Recent epidemiologic studies suggest that Takayasu arteritis is being increasingly recognized in Europe. The first symptoms are non-specific and an early diagnosis is difficult and requires clinical awareness and suspicion. Patients with Takayasu arteritis often present increased inflammatory markers, including C-reactive protein and erythrocyte sedimentation rate, but systemic inflammatory response does not always show a positive correlation with inflammatory activity in the vessel wall. Therefore, imaging studies play a principal role in diagnosis and control of the disease. Glucocorticoids remain the most effective and serve as a cornerstone first line treatment. Immunosuppressive drugs play an important role as well, and biological therapy is increasingly being included in the treatment. This article describes the epidemiology, pathophysiology, diagnostics and treatment of this rare disease, so as to alert clinicians because disease left untreated can lead to narrowing and even closure of vital blood vessels. The most common Takayasu arteritis complications include pulmonary thrombosis, aortic regurgitation, congestive heart failure, cerebrovascular events, vision degeneration or blindness, and hearing problems.

Demonstration of the IgG antibody repertoire against the bacteria Escherichia coli in Chinese intravenous immunoglobulins

Intravenous immunoglobulin (IVIg) is produced by pooling plasma from thousands of healthy blood donors, and the diversity of the antibody is critical for the clinical efficacy of IVIg. This study investigated the antibody diversity of Chinese IVIg. Firstly, 2-dimensional gel electrophoresis and immunoblotting with protein extracts of Escherichia coli (E. coli) O157:H7 were used to study IgG antibody repertoire of 8 IVIg preparations from different Chinese manufacturers. This was followed by the identification of the antibody-reactive proteins of E. coli by mass spectrometry and the sequence similarity of the proteins was aligned by bioinformatics analysis. The results showed that all IVIg preparations expressed a large range of antibody reactivities against E. coli proteins. 94-238 antigens were recognized by the 8 IVIg preparations. 33 interesting target antigens were selected and identified as 29 different proteins, mainly including membrane proteins, molecular chaperones, metabolism enzymes, and proteins involved in cell cycle processes. Additionally, these antigens were highly conserved proteins which were found extensively in a variety of other pathogenic microorganisms. Our study indicated that Chinese IVIg preparations recognized a large range of high conserved proteins which play key roles in pathogenic microorganisms, and showed each IVIg had its own distinct antibody repertoire.

Circulating antibodies to α-enolase and phospholipase A2 receptor and composition of glomerular deposits in Japanese patients with primary or secondary membranous nephropathy

Background

Phospholipase A₂ receptor (PLA₂R) is recognized as a target antigen in primary membranous nephropathy (MN); Anti-α-enolase antibody in primary and secondary MN has been proposed, however, little is known about the potential contribution of α-enolase to the pathogenesis of MN.

Methods

We evaluated circulating antibodies to α-enolase by a dot blotting system and PLA₂R by indirect immunofluorescence, and glomerular deposition of these proteins in 25 patients with primary MN, 20 patients with secondary MN, 44 patients with collagen disease or severe infection, 60 patients with nephritis (each ten patients of IgA nephropathy, focal segmental gloemrulosclerosis, minimal change nephrotic syndrome, membranoproliferative glomeurlonephritis, diabetic glomerulosclerosis, and tubulointerstitial nephritis) as disease control, and 20 healthy subjects.

Results

In primary MN, 18 of 25 sera (72 %) showed anti-α-enolase antibody (IgG1 and IgG4, 11 pts; IgG4 alone, six pts; IgG1 alone, one pt). In secondary MN, 15 of 20 sera (75 %) contained anti-α-enolase antibody (IgG1 and IgG3, 13 pts; IgG3 alone, two pts). No circulating anti-α-enolase antibody was found in 44 collagen diseases or septic patients, 60 nephritis without MN, and 20 healthy subjects. Twelve of 25 sera (48 %) from patients with primary MN were positive for anti-PLA₂R antibody, whereas all patients with secondary MN were negative. Eight of the 12 PLA₂R-positive patients (67 %) with primary MN also had anti α-enolase antibody. Although PLA₂R antigen was present in a subepithelial pattern in 10 of 19 (52 %) patients with primary MN, α-enolase was never detected in glomerular deposits in 19 and ten patients with primary and secondary MN, respectively.

Conclusions

Circulating anti-α-enolase antibodies are highly present in both primary and secondary MN (about 70 %, respectively), while anti-PLA₂R antibodies are specific for primary MN (48 %) with a prevalence apparently lower in the Japanese population than in Chinese and Caucasian populations. The absence of α-enolase from subepithelial immune deposits suggests that anti-α-enolase antibodies do not contribute directly to immune-deposit formation, although they may have other pathogenic effects.

Electronic supplementary material

The online version of this article (doi:10.1007/s10157-016-1235-2) contains supplementary material, which is available to authorized users.

Detection of Antibodies In Vitro Binding to Endothelial Cells in the Sera from Women with Normal Pregnancy and Preeclampsia

Activity of serum antibodies in vitro binding to endothelial cells in women with normal pregnancy and preeclampsia was studied. Flow cytometry detected peculiarities of antibody binding to endothelial cells in health and disease. Detection of antiendothelial antibodies in trimesters II and III can be diagnostically important in preeclampsia.

An Optimized Fluorescence-Based Bidimensional Immunoproteomic Approach for Accurate Screening of Autoantibodies

Serological proteome analysis (SERPA) combines classical proteomic technology with effective separation of cellular protein extracts on two-dimensional gel electrophoresis, western blotting, and identification of the antigenic spot of interest by mass spectrometry. A critical point is related to the antigenic target characterization by mass spectrometry, which depends on the accuracy of the matching of antigenic reactivities on the protein spots during the 2D immunoproteomic procedures. The superimposition, based essentially on visual criteria of antigenic and protein spots, remains the major limitation of SERPA. The introduction of fluorescent dyes in proteomic strategies, commonly known as 2D-DIGE (differential in-gel electrophoresis), has boosted the qualitative capabilities of 2D electrophoresis. Based on this 2D-DIGE strategy, we have improved the conventional SERPA by developing a new and entirely fluorescence-based bi-dimensional immunoproteomic (FBIP) analysis, performed with three fluorescent dyes. To optimize the alignment of the different antigenic maps, we introduced a landmark map composed of a combination of specific antibodies. This methodological development allows simultaneous revelation of the antigenic, landmark and proteomic maps on each immunoblot. A computer-assisted process using commercially available software automatically leads to the superimposition of the different maps, ensuring accurate localization of antigenic spots of interest.

Association of ferritin antibodies with Takayasu arteritis

Takayasu arteritis (TA) is difficult to diagnose because diagnostic biomarkers have not yet been established. In a previous study, we detected autoantibodies against the human ferritin heavy chain protein (HFC) in the sera of patients with giant cell arteritis (GCA) and/or polymyalgia rheumatica (PMR). The aim of this study is to evaluate the frequency of autoantibodies against HFC in TA. We established seven ELISA assays for the detection of autoantibodies against HFC. We used the full-length recombinant HFC expressed in Escherichia coli or one of six different HFC peptides as autoantigens: 1-18Aa (98.8 % purity), 19-45Aa (98.8 % purity), 52-78Aa (98.3 % purity), 79-104Aa (98.8 % purity), 105-143Aa (98.4 % purity) and 145-183Aa (98.5 % purity). We collected sera from 48 patients with TA, 36 patients with systemic lupus erythematosus (SLE), 35 patients with arteriosclerosis, 133 patients with febrile diseases, which are known to generate unspecific autoantibodies, and 50 blood donors, which served as controls. The best results were obtained using the ferritin peptides as antigens. By combining the results from the different ELISAs that detect autoantibodies against the HFC peptides 19-44A, 79-104A and 105-144A, we were able to detect ferritin peptide antibodies in 30/48 (62 %) of the TA patients. The frequency was lower than in early GCA and PMR (previous study showed up to 92 %). Positive results were observed in 0/50 (0 %) of the control blood donors, 10/36 (28 %) of the SLE patients, 4/35 (11 %) of the arteriosclerosis patients and 27/133 (20 %) of the fever patients. Considering the lack of biomarkers for TA, autoantibodies against HFC peptides could act as useful markers for TA.

Susac's syndrome--pathogenesis, clinical variants and treatment approaches

Susac's syndrome is a rare disease that is characterised by the clinical triad of encephalopathy, branch retinal artery occlusion, and sensorineural hearing loss. It was first described as a distinctive syndrome by Susac in 1979. There have been 304 reported individual patients with Susac's syndrome. Etiopathogenesis is not clear, although it is now thought that it is an immune-mediated endotheliopathy that affects the microvasculature of the brain, retina, and inner ear. Antiendothelial cell antibodies (AECAs) play an important role in mediating the endothelial cell injury with consequent deposition of thrombotic material in the lumen of the small vessel. In biopsies of the brain, microinfarcts with atrophy of the white and grey matter could be detected. These microinfarcts are caused by a microangiopathic process with arteriolar wall proliferation, lymphocytic infiltration and basal lamina thickening. At clinical onset, the most common manifestation was central nervous system symptoms, followed by visual symptoms and hearing disturbances. Diagnosis is based on Magnetic Resonance Imaging (MRI), retinal fluorescein angiography, and audiometry; these are considered crucial tests to enable diagnosis. Antiendothelial cell antibodies (AECAs) are also of diagnostic relevance. Based on the hypothesis of being an autoimmune disease, treatment has to be immunosuppressive. In addition, anticoagulation measures, antiplatelet agents and antivasospastic agents should be considered. The majority of patients did not initially present with the complete triad of symptoms. An appropriate approach would be to perform a search for absent components of the triad if the clinical presentation is suggestive of Susac's syndrome. Improved understanding of the presentation of Susac's syndrome will prevent misdiagnosis and ensure that patients receive the best possible care.

Autoantibody profiling in multiple sclerosis using arrays of human protein fragments

Profiling the autoantibody repertoire with large antigen collections is emerging as a powerful tool for the identification of biomarkers for autoimmune diseases. Here, a systematic and undirected approach was taken to screen for profiles of IgG in human plasma from 90 individuals with multiple sclerosis related diagnoses. Reactivity pattern of 11,520 protein fragments (representing ∼38% of all human protein encoding genes) were generated on planar protein microarrays built within the Human Protein Atlas. For more than 2,000 antigens IgG reactivity was observed, among which 64% were found only in single individuals. We used reactivity distributions among multiple sclerosis subgroups to select 384 antigens, which were then re-evaluated on planar microarrays, corroborated with suspension bead arrays in a larger cohort (n = 376) and confirmed for specificity in inhibition assays. Among the heterogeneous pattern within and across multiple sclerosis subtypes, differences in recognition frequencies were found for 51 antigens, which were enriched for proteins of transcriptional regulation. In conclusion, using protein fragments and complementary high-throughput protein array platforms facilitated an alternative route to discovery and verification of potentially disease-associated autoimmunity signatures, that are now proposed as additional antigens for large-scale validation studies across multiple sclerosis biobanks.

Antiendothelial cells antibodies in patients with systemic sclerosis in relation to pulmonary hypertension and lung fibrosis

Although scleroderma is generally considered a fibrosing disease, it is now recognized that the underlying vascular pathology is playing a fundamental role in its pathogenesis. The present study was aimed at testing the prevalence of anti-endothelial cell antibodies (AECA) in systemic scleroderma (SSc) patients with and without pulmonary hypertension (PH) and in relation to the presence of pulmonary fibrosis. Fifty four SSc patients (50 females and 4 male, mean age 55.7 ± 16.3 years) were prospectively screened. All patients underwent transthoracic echocardiography with the estimation of pulmonary artery pressure (PAP) and tricuspid regurgitant peak gradient (TRPG). All patients suspected to have pulmonary hypertension were referred for right heart catheterization. Restrictive lung disease was confirmed by HRCT. A healthy control group included (n = 27; 7 men and 20 women, mean age 49.8 ± 12.1 years). The study of AECA was performed using the indirect immunofluorescence method on commercially available human umbilical vein endothelial cells. The HRCT scans in patients with suspected interstitial lung disease revealed signs of lung fibrosis in 15 (out of the 36 examined patients). TRPG at rest of 31 mmHg was demonstrated in 14 (21%) patients. During cardiac catheterization, arterial PH was found in two patients. Resting venous PH was found in one patient and an excessive post capillary PAP elevation at rest was demonstrated in 11 patients. At the baseline, 14/54 patients (26%) were positive for AECA. In the control group, the frequency of the antibodies was 3/27 (11%). No statistical correlation between antibody titter and the presentation of the disease existed. AECA were highly prevalent in a subgroup of patients suffering from interstitial pulmonary fibrosis. Out of the 15 patients suffering from lung fibrosis, 7 were AECA positive. The presence of AECA correlated very well with antinuclear antibodies (ANA), but was not related to the profile of ANA. Our findings support evidence that endothelial cell damage is involved in SSc, as there was increased prevalence of circulating AECA of the IgG isotype in SSc patients. AECA may also be related to the complications of SSc, like pulmonary fibrosis.

In vitro and in vivo properties differ among liquid intravenous immunoglobulin preparations

Objective To compare in vitro and in vivo biological and biochemical properties of five liquid intravenous immunoglobulin (IVIg) preparations licensed for therapeutic use in Europe.

Methods ClairYg® was compared in a blinded manner to four other liquid IVIg preparations licensed in Europe (Octagam®, Kiovig®, Gamunex®, Privigen®). Three batches of each preparation were tested, except for the IgG repertoires and the animal model.

Results Levels of anti-A and anti-B antibodies were lower in ClairYg® (0·11/0·11) relative to a positive EDQM standard and Octagam® (0·11/0·08) than in other preparations (0·33–0·69/0·42–0·46). IgG in ClairYg® recognized 365 and 416 protein spots in HEp-2 cell and Escherichia coli protein extracts vs. 230–330 and 402–842 protein spots, respectively, for IgG in other preparations. IgA content (301 vs. 165–820 ng/mg of IgG), Factor XI and Factor XII antigen (0·46 vs. 0·85–2·40 mU/mg of IgG and 7·8 vs. 20·0–46·2 lU/mg of IgG) C1q binding (0·42 vs. 0·67–1·89 arbitrary units) and C5a uptake (0·41 vs. 0·45–0·66% of activation) were lower in ClairYg® than in other preparations. Finally, intravenous infusion of ClairYg®, Gamunex® and Privigen® had no major effect on arterial blood pressure in spontaneously hypertensive rats.

Conclusions Our results evidence some differences in the biological and biochemical properties among licensed liquid IVIg preparations.

IgG from patients with pulmonary arterial hypertension and/or systemic sclerosis binds to vascular smooth muscle cells and induces cell contraction

OBJECTIVES

Pulmonary arterial hypertension (PAH) is characterised by remodelling of pulmonary arteries with enhanced vascular smooth muscle cell (VSMC) contraction, migration and proliferation. The authors investigated the presence of antibodies to human VSMCs in the serum of patients with systemic sclerosis with or without PAH and idiopathic PAH (iPAH).

METHODS AND RESULTS

Antibodies to VSMCs were detected by immunofluorescence in sera from healthy controls and patients with scleroderma without PAH, scleroderma-associated PAH and iPAH. Serum IgG from these patients induced contraction of VSMCs in a collagen matrix in contrast with IgG from healthy controls. Several protein spots of interest and target antigens were identified by two-dimensional immunoblotting and MS, including stress-induced phosphoprotein 1 and α-enolase. Finally, antibodies to stress-induced phosphoprotein 1 were detected by ELISA in sera from 84%, 76% and 24% of patients with scleroderma without PAH, scleroderma-associated PAH and iPAH, respectively, compared with only 3% of healthy controls.

CONCLUSION

The authors have identified IgG that binds to VSMCs in the serum of patients with scleroderma and iPAH. These antibodies may be pathogenic by modulating vascular contraction. The target antigens of these antibodies are stress-induced phosphoprotein 1 and α-enolase.

Induction of elastin expression in vascular endothelial cells relates to hepatoportal sclerosis in idiopathic portal hypertension: possible link to serum anti-endothelial cell antibodies

Hepatoportal sclerosis accompanied by dense elastic fibre deposition is generally regarded as the primary lesion in the development of idiopathic portal hypertension (IPH). This study was performed to clarify the mechanism of elastic fibre deposition in the peripheral portal tracts of IPH liver in relation to serum anti-endothelial cell antibodies (AECA). In-vitro experiments were performed using human dermal microvascular endothelial cells (HMVEC) and patients' sera. The presence of serum AECA was assayed by a cell-based enzyme-linked immunosorbent assay (ELISA) using HMVEC. Immunohistochemical analysis of elastin was performed using liver tissue sections of IPH patients. IPH sera contained one or more AECA that could bind to the vascular endothelial cells of the peripheral portal tracts of the liver. When the value of AECA greater than the mean ± 2 standard deviations of healthy controls was regarded as positive, the positive detection rate of either immunoglobulin (Ig)G, IgA or IgM AECA in IPH sera was 30% (10 of 33 cases). IPH sera induced the expression of elastin in HMVEC, which appeared to be associated with the presence of AECA. Apoptosis was also induced in HMVEC by the stimulation with IPH sera. In vivo, elastin expression was observed in the endothelial cells of the peripheral portal tracts of IPH livers in a proportion of cases. The disease pathogenesis of IPH seems to be heterogeneous, and this study elucidated a possible contribution of the induction of elastin expression in the portal vessels to hepatoportal sclerosis of IPH, which might be linked to serum AECA as a causative factor.

Susac syndrome: an organ-specific autoimmune endotheliopathy syndrome associated with anti-endothelial cell antibodies

Susac syndrome (SS) is the triad of encephalopathy, branch retinal artery occlusions (BRAOs), and hearing loss. Migraines may herald and accompany encephalopathy. Little is known about pathogenesis. Based on light microscopic findings in brain biopsy material analogous to anti-endothelial cell antibody (AECA)-mediated microvascular injury, we postulated that SS microangiopathy was attributable to AECAs. We examined serum samples from 11 patients with SS for AECAs; 9 were positive by indirect immunofluorescence and Western blot studies. A highly distinctive band on Western blots corresponding to a 50-kDa protein was observed in 8 positive SS samples; the other positive case exhibited specific reactivity with a protein band at 40 kDa. Of the 2 negative cases, 1 had been inactive since 1988; the other was an abortive variant characterized solely by BRAOs. There was enhanced surface binding of SS serum using live endothelial cell substrates compared with samples from healthy subjects. Additional serum samples from apparently healthy patients, 2 with atypical migraines, and patients with other forms of autoinflammatory disease did not show the distinctive band of immunoreactivity. SS is a distinct autoimmune endotheliopathy syndrome associated with AECAs; the antibody target seems specific in many cases and may be a disease biomarker. The exact role of AECAs in disease propagation remains unanswered.

Identification of target antigens of anti-endothelial cell and anti-vascular smooth muscle cell antibodies in patients with giant cell arteritis: a proteomic approach

Introduction

Immunological studies of giant cell arteritis (GCA) suggest that a triggering antigen of unknown nature could generate a specific immune response. We thus decided to detect autoantibodies directed against endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) in the serum of GCA patients and to identify their target antigens.

Methods

Sera from 15 GCA patients were tested in 5 pools of 3 patients' sera and compared to a sera pool from 12 healthy controls (HCs). Serum immunoglobulin G (IgG) reactivity was analysed by 2-D electrophoresis and immunoblotting with antigens from human umbilical vein ECs (HUVECs) and mammary artery VSMCs. Target antigens were identified by mass spectrometry.

Results

Serum IgG from GCA patients recognised 162 ± 3 (mean ± SD) and 100 ± 17 (mean ± SD) protein spots from HUVECs and VSMCs, respectively, and that from HCs recognised 79 and 94 protein spots, respectively. In total, 30 spots from HUVECs and 19 from VSMCs were recognised by at least two-thirds and three-fifths, respectively, of the pools of sera from GCA patients and not by sera from HCs. Among identified proteins, we found vinculin, lamin A/C, voltage-dependent anion-selective channel protein 2, annexin V and other proteins involved in cell energy metabolism and key cellular pathways. Ingenuity pathway analysis revealed that most identified target antigens interacted with growth factor receptor-bound protein 2.

Conclusions

IgG antibodies to proteins in the proteome of ECs and VSMCs are present in the sera of GCA patients and recognise cellular targets that play key roles in cell biology and maintenance of homeostasis. Their potential pathogenic role remains to be determined.

Identification of new autoantibody specificities directed at proteins involved in the transforming growth factor β pathway in patients with systemic sclerosis

Introduction

Antinuclear antibodies (ANAs), usually detected by indirect immunofluorescence on HEp-2 cells, are identified in 90% of patients with systemic sclerosis (SSc). Thus, approximately 10% of SSc patients have no routinely detectable autoantibodies, and for 20% to 40% of those with detectable ANAs, the ANAs do not have identified specificity (unidentified ANAs). In this work, we aimed to identify new target autoantigens in SSc patients.

Methods

Using a proteomic approach combining two-dimensional electrophoresis and immunoblotting with HEp-2 cell total and enriched nuclear protein extracts as sources of autoantigens, we systematically analysed autoantibodies in SSc patients. Sera from 45 SSc patients were tested in 15 pools from groups of three patients with the same phenotype. A sera pool from 12 healthy individuals was used as a control. Proteins of interest were identified by mass spectrometry and analysed using Pathway Studio software.

Results

We identified 974 and 832 protein spots in HEp-2 cell total and enriched nuclear protein extracts, respectively. Interestingly, α-enolase was recognised by immunoglobulin G (IgG) from all pools of patients in both extracts. Fourteen and four proteins were recognised by IgG from at least 75% of the 15 pools in total and enriched nuclear protein extracts, respectively, whereas 15 protein spots were specifically recognised by IgG from at least four of the ten pools from patients with unidentified ANAs. The IgG intensity for a number of antigens was higher in sera from patients than in sera from healthy controls. These antigens included triosephosphate isomerase, superoxide dismutase mitochondrial precursor, heterogeneous nuclear ribonucleoprotein L and lamin A/C. In addition, peroxiredoxin 2, cofilin 1 and calreticulin were specifically recognised by sera from phenotypic subsets of patients with unidentified ANAs. Interestingly, several identified target antigens were involved in the transforming growth factor β pathway.

Conclusions

We identified several new target antigens shared among patients with SSc or specific to a given phenotype. The specification of new autoantibodies could help in understanding the pathophysiology of SSc. Moreover, these autoantibodies could represent new diagnostic and/or prognostic markers for SSc.

Venous and arterial endothelial proteomics: mining for markers and mechanisms of endothelial diversity

Endothelial cells (ECs) line the inside of arterial and venous blood vessels in a continuous monolayer and have the important function of responding to environmental cues to regulate vascular tone and new blood vessel formation. They also have well-defined roles in supporting tumorigenesis, and alterations in their function lead to cardiovascular disease. Consequently, ECs have been studied extensively as a cellular model of both normal and abnormal physiology. Despite their importance and the increased utility of proteomic tools in medical research, there are relatively few publications on the topic of vascular endothelial proteomics. A thorough search of the literature mined 52 publications focused exclusively on arterial and/or venous endothelial proteomics. These studies mostly relied upon examination of whole-cell lysates from cultured human umbilical vein ECs to investigate in vitro effects of various molecules, such as VEGF in the context of altering human umbilical vein EC functions related to angiogenesis. Only a few of these publications focused solely on a proteomic characterization of ECs and our analysis further revealed a lack of published studies incorporating proteomic analysis of freshly isolated ECs from tissues or in vitro conditions that mimic in vivo variables, such as oxygen tension and shear stress. It is the purpose of this article to account for the diversity of vascular EC proteomic investigations and comment on the issues that have been and should be addressed in future work.

Targeting ADAM-17/notch signaling abrogates the development of systemic sclerosis in a murine model

OBJECTIVE

Systemic sclerosis (SSc) is characterized by the fibrosis of various organs, vascular hyperreactivity, and immunologic dysregulation. Since Notch signaling is known to affect fibroblast homeostasis, angiogenesis, and lymphocyte development, we undertook this study to investigate the role of the Notch pathway in human and murine SSc.

METHODS

SSc was induced in BALB/c mice by subcutaneous injections of HOCl every day for 6 weeks. Notch activation was analyzed in tissues from mice with SSc and from patients with scleroderma. Mice with SSc were either treated or not treated with the γ-secretase inhibitor DAPT, a specific inhibitor of the Notch pathway, and the severity of the disease was evaluated.

RESULTS

As previously described, mice exposed to HOCl developed a diffuse cutaneous SSc with pulmonary fibrosis and anti-DNA topoisomerase I antibodies. The Notch pathway was hyperactivated in the skin, lung, fibroblasts, and splenocytes of diseased mice and in skin biopsy samples from patients with scleroderma. ADAM-17, a proteinase involved in Notch activation, was overexpressed in the skin of mice and patients in response to the local production of reactive oxygen species. In HOCl-injected mice, DAPT significantly reduced the development of skin and lung fibrosis, decreased skin fibroblast proliferation and ex vivo serum-induced endothelial H(2)O(2) production, and abrogated the production of anti-DNA topoisomerase I antibodies.

CONCLUSION

Our results show the pivotal role of the ADAM-17/Notch pathway in SSc following activation by reactive oxygen species. The inhibition of this pathway may represent a new treatment of this life-threatening disease.

Immunogenicity of SEREX-identified antigens and disease outcome in pancreatic cancer

Despite spontaneous or vaccination-induced immune responses, pancreatic cancer remains one of the most deadly immunotherapy-resistant malignancies. We sought to comprehend the spectrum of pancreatic tumor-associated antigens (pTAAs) and to assess the clinical relevance of their immunogenicity. An autologous SEREX-based screening of a cDNA library constructed from a pancreatic T3N0M0/GIII specimen belonging to a long-term survivor (36 months) revealed 18 immunogenic pTAA. RT-PCR analysis displayed broad distribution of the identified antigens among normal human tissues. PNLIPRP2 and MIA demonstrated the most distinct pancreatic cancer-specific patterns. ELISA-based screening of sera for corresponding autoantibodies revealed that although significantly increased, the immunogenicity of these molecules was not a common feature in pancreatic cancer. QRT-PCR and immunohistochemistry characterized PNLIPRP2 as a robust acinar cell-specific marker whose decreased expression mirrored the disappearance of parenchyma in the diseased organ, but was not related to the presence of PNLIPRP2 autoantibodies. Analyses of MIA-known to be preferentially expressed in malignant cells-surprisingly revealed an inverse correlation between intratumoral gene expression and the emergence of autoantibodies. MIA(high) patients were autoantibody-negative and had shorter median survival when compared with autoantibody-positive MIA(low) patients (12 vs. 34 months). The observed pTAA spectrum comprised molecules associated with acinar, stromal and malignant structures, thus presenting novel targets for tumor cell-specific therapies as well as for approaches based on the bystander effects. Applying the concept of cancer immunoediting to interpret relationships between gene expression, antitumor immune responses, and clinical outcome might better discriminate between past and ongoing immune responses, consequently enabling prognostic stratification of patients and individual adjustment of immunotherapy.

Antifibroblast antibodies from systemic sclerosis patients bind to {alpha}-enolase and are associated with interstitial lung disease

OBJECTIVE

To identify target antigens of antifibroblast antibodies (AFA) in systemic sclerosis (SSc) patients.

PATIENTS AND METHODS

In the first part, sera from 24 SSc patients (12 with pulmonary arterial hypertension (PAH) and 12 without) and 36 idiopathic PAH patients, tested in pooled sera for groups of three, were compared with a sera pool from 14 healthy controls (HC). Serum IgG reactivity was analysed by the use of a two-dimensional electrophoresis and immunoblotting technique with normal human fibroblasts antigens. In the second part, serum IgG reactivity for two groups: 158 SSc, 67 idiopathic PAH and 100 HC; and 35 SSc and 50 HC was tested against alpha-enolase from Saccharomyces cerevisiae and recombinant human (rHu) alpha-enolase, respectively, on ELISA.

RESULTS

In the first part, alpha-enolase was identified as a main target antigen of AFA from SSc patients. In the second part, 37/158 (23%) SSc patients, 6/67 (9%) idiopathic PAH patients and 4/100 (4%) HC (p<0.001) had anti-S cerevisiae alpha-enolase antibodies; 12/35 (34%) SSc patients and 3/50 (6%) HC had anti-rHu alpha-enolase antibodies (p = 0.001). In SSc, the presence of anti-S cerevisiae alpha-enolase antibodies was associated with interstitial lung disease (ILD), decreased total lung capacity (73.2% vs 89.7%; p<0.001) and diffusion capacity for carbon monoxide (47.4% vs 62.3%; p<0.001), and antitopoisomerase 1 antibodies (46% vs 21%; p = 0.005) but not anticentromere antibodies (11% vs 34%; p = 0.006). Results were similar with rHu alpha-enolase testing.

CONCLUSION

In SSc, AFA recognise alpha-enolase and are associated with ILD and antitopoisomerase antibodies.

Identification of target antigens of self-reactive IgG in intravenous immunoglobulin preparations

Intravenous immunoglobulin (IVIg) contains a wide range of self-reactive immunoglobulins (Ig) G. Acidic pH is known to increase the reactivity of purified IgG with self-antigens. We describe here the target antigens of IgG autoantibodies in IVIg and analyze the influence of acidic pH on IgG reactivities. We used 2-DE and immunoblotting with protein extracts of human umbilical vein endothelial cells (HUVEC) and HEp-2 cells. Two IVIg preparations obtained by ethanol fractionation [one with an acidic pH step (acidic-IVIg) and one with beta-propiolactone (propiolactone-IVIg)] and a pool of sera from 12 healthy individuals were tested. Serum IgG of 3 healthy individuals and IgG purified from the same sera with elution at pH 2.8 were also tested individually. Finally, propiolactone-IVIg was acidified at pH 2.8. IgG obtained with a step at low pH recognized many more target spots than IgG obtained without acidic pH. Our findings demonstrate that an acidic pH step artificially enlarges the repertoire of self-reactive IgG. Thus, protein spots recognized by IgG in propiolactone-IVIg represent the core set of self-antigens targeted by IVIg. Overall, 96 proteins were identified by MS. Fourteen were recognized in both extracts including glycolysis proteins such as alpha-enolase, RNA processing and cytoskeletal proteins such as lamin-A/C.

Hashimoto's encephalopathy

Hashimoto's encephalopathy (HE) is a controversial neurological disorder that comprises a heterogenous group of neurological symptoms that manifest in patients with high titers of antithyroid antibodies. Clinical manifestations of HE may include encephalopathic features such as seizures, behavioral and psychiatric manifestations, movement disorders, and coma. Although it has been linked to cases of Hashimoto's thyroiditis or thyroid dysfunction, the most common immunological feature of HE is the presence of high titers of antithyroglobulin or anti-TPO (antimicrosomal) antibodies. At present, it is unclear whether antithyroid antibodies represent an immune epiphenomenon in a subset of patients with encephalopathic processes or they are really associated with pathogenic mechanisms of the disorder. The significance of classifying encephalopathies under the term HE will be determined in the future once the relevance of the role of antithyroid antibodies is demonstrated or dismissed by more detailed experimental and immunopathological studies. The responsiveness of HE to steroids or other therapies such as plasmapheresis supports the hypothesis that this is a disorder that involves immune pathogenic mechanisms. Further controlled studies of the use of steroids, plasmapheresis, or immunosuppressant medications are needed in the future to prove the concept of the pathogenic role of antithyroid antibodies in HE.

Antiendothelial cells autoantibodies in vasculitis-associated systemic diseases

Antiendothelial cell antibodies (AECA) have been detected in healthy individuals, as well as in autoimmune and systemic inflammatory diseases, including systemic vasculitides. AECA have been reported in large vessel vasculitides such as giant cell arteritis and Takayasu arteritis; medium-sized vessel vasculitides, such as polyarteritis nodosa related to hepatitis B virus infection and Kawasaki disease; and small-sized vessel vasculitides, such as Wegener's granulomatosis, microscopic polyangiitis, and Henoch-Schonlein purpura. In Takayasu arteritis and antineutrophil cytoplasm antibody-positive vasculitides, AECA have been reported to correlate with disease activity. A cell-based enzyme-linked immunosorbent assay (ELISA) using cultured human umbilical vein endothelial cells (HUVEC) represent one of the reference techniques for AECA detection, although flow cytometry and immunobloting have also been proposed. AECA might contribute to the pathogenesis of systemic vasculitides and vasculitis-associated diseases through (1) activation of endothelial cells (EC), (2) direct cytotoxic effect due to complement-dependent cytotoxicity or indirect cytotoxic effect secondary to antibody-dependent cytotoxicity, (3) induction of coagulation, (4) induction of apoptosis through the binding of phospholipids or heat-shock protein 60, and (5) induction of EC activation. None of the identified target antigens of AECA is specific for EC, and EC-specific target antigens of AECA remain to be identified in systemic vasculitides.

Natural anti-endothelial cell antibodies

Anti-endothelial cell antibodies (AECA) are detectable in a heterogenous group of autoimmune and inflammatory conditions. These antibodies have also been detected in healthy individuals. Nevertheless, most of the literature focuses on AECA in pathological conditions and their targets and functions in healthy individuals remain to be clarified. Recently, proteome-based technologies have been successfully used for the identification of antigens targeted by natural AECA. Thus, it has been shown that IgG AECA can be detected in sera from healthy individuals that recognize a restricted set of proteins among a whole protein extract of umbilical vein endothelial cells. These proteins correspond to ubiquitous proteins belonging to highly conserved protein families and exerting pivotal roles in cell physiology, including cytoskeletal proteins (beta actin, vimentin, alpha tubulin) and glycolytic enzymes (glyceraldehyde-3-phosphate-deshydrogenase and alpha-enolase). As reported for other types of natural autoantibodies, natural AECA could exert anti-inflammatory and anti-thrombotic functions. In addition, they could play a role in the control of EC activation.