Value of isolated IgA anti-β2 -glycoprotein I positivity in the diagnosis of the antiphospholipid syndrome

IgA anti-β2 glycoprotein I antibodies: Experience from a large center

OBJECTIVE

IgG and IgM antibodies directed at β2-glycoprotein I are included in the classification criteria for the antiphospholipid syndrome (APS) while the IgA antibodies against β2-glycoprotein I (IgA aβ2GPI) are not. Conflicting data about the significance of IgA aβ2GPI and APS manifestation can be found and more studies are necessary in order to define the diagnostic value of IgA aβ2GPI. In the present article, we investigated the possible role of IgA aβ2GPI as marker of APS.

METHODS

A cohort of 314 patients with APS and systemic autoimmune disease was investigated for the presence of IgA aβ2GPI and its association with clinical manifestation of APS.

RESULTS

Eighty-nine patients presented IgA aβ2GPI, 68 cases associated with others antiphospholipid antibodies (aPL) and in 21 cases being the only aPL present. In primary APS IgA aβ2GPI are highly coincidental with other aPL (92,2%) while most of the isolated IgA aβ2GPI were present in the SLE group (16/21). No association between IgA aβ2GPI and APS manifestations: thrombosis and pregnancy morbidity was found, while a positive association between IgA aβ2GPI and the presence of anti-nDNA, anti-RNP, anti-Sm, anti-SSA, anti-SSB antibodies was encountered.

CONCLUSION

Our study does not show association between IgA aβ2GPI and APS manifestations and does not support the inclusion of IgA aβ2GPI as a classification criteria for APS.

Diagnosing antiphospholipid syndrome: 'extra-criteria' manifestations and technical advances

First described in the early 1980s, antiphospholipid syndrome (APS) is a unique form of acquired autoimmune thrombophilia in which patients present with clinical features of recurrent thrombosis and pregnancy morbidity and persistently test positive for the presence of antiphospholipid antibodies (aPL). At least one clinical (vascular thrombosis or pregnancy morbidity) and one lab-based (positive test result for lupus anticoagulant, anticardiolipin antibodies and/or anti-β2-glycoprotein 1 antibodies) criterion have to be met for a patient to be classified as having APS. However, the clinical spectrum of APS encompasses additional manifestations that can affect many organs and cannot be explained exclusively by patients being in a prothrombotic state; clinical manifestations not listed in the classification criteria (known as extra-criteria manifestations) include neurologic manifestations (chorea, myelitis and migraine), haematologic manifestations (thrombocytopenia and haemolytic anaemia), livedo reticularis, nephropathy and valvular heart disease. Increasingly, research interest has focused on the development of novel assays that might be more specific for APS than the current aPL tests. This Review focuses on the current classification criteria for APS, presenting the role of extra-criteria manifestations and lab-based tests. Diagnostic approaches to difficult cases, including so-called seronegative APS, are also discussed.

Incidence of thromboembolic events in asymptomatic carriers of IgA anti ß2 glycoprotein-I antibodies

BACKGROUND

The antiphospholipid syndrome (APS) is defined by simultaneous presence of vascular clinical events and antiphospholipid antibodies (aPL). The aPL considered as diagnostics are lupus anticoagulant and antibodies anticardiolipin (aCL) and anti-ß2 glycoprotein-I (aB2GP1). During recent years, IgA aB2GP1 antibodies have been associated with thrombotic events both in patients positive, and mainly negative for other aPL, however its value as a pro-thrombotic risk-factor in asymptomatic patients has not been well defined.

OBJECTIVE

To test the role of IgA anti B2GP1 as a risk factor for the development of APS-events (thrombosis or pregnancy morbidity) in asymptomatic population with a 5-year follow-up.

METHODS

244 patients isolated positive for anti-beta2-glycoprotein I IgA (Group-1 study) and 221 negative patients (Group-2 control) were studied. All the patients were negative for IgG and IgM aCL.

RESULTS

During the follow-up, 45 patients (9.7%) had APS-events, 38 positive for IgA-aB2GP1 and 7 negative (15.6% vs 3.2%, p<0.001). The incidence rate of APS-events was 3.1% per year in IgA-aB2GP1 positive patients and 0.6% per year in the control group. Arterial thrombosis were the most frequent APS-events (N = 25, 55%) and were mainly observed in Group-1 patients (21 vs 4, p = 0.001). Multivariate analysis were shown as independent risk-factors for the development of APS-events, age, sex (men) and presence of IgA-aB2GP1 (odds ratio 5.25, 95% CI 2.24 to 12.32).

CONCLUSION

The presence of IgA-aB2GP1 in people with no history of APS-events is the main independent risk factor for the development of these types of events, mainly arterial thrombosis.

Evaluation of three fully automated immunoassay systems for detection of IgA anti-beta 2-glycoprotein I antibodies

INTRODUCTION

In recent years, we have been witnessing increased clinical interest in the determination of IgA anti-beta 2-glycoprotein I (aB2GPI) antibodies as well as increased demand for this test. Some ELISA-based diagnostic systems for IgA aB2GPI antibodies detection are suboptimal to detect it. The aim of our study was to determine whether the diagnostic yield of modern detection systems based on automatic platforms to measure IgA aB2GPI is equivalent to that of the well-optimized ELISA-based assays.

METHODS

In total, 130 patients were analyzed for IgA aB2GPI by three fully automated immunoassays using an ELISA-based assay as reference. The three systems were also analyzed for IgG aB2GPI with 58 patients.

RESULTS

System 1 was able to detect IgA aB2GPI with good sensitivity and kappa index (99% and 0.72, respectively). The other two systems had also poor sensitivity (20% and 15%) and kappa index (0.10 and 0.07), respectively. On the other hand, kappa index for IgG aB2GPI was >0.89 in the three systems.

CONCLUSION

Some analytical methods to detect IgA aB2GPI are suboptimal as well as some ELISA-based diagnostic systems. It is important that the scientific community work to standardize analytical methods to determine IgA aB2GPI antibodies.

Antiphospholipid Syndrome and Kidney Involvement: New Insights

Antiphospholipid syndrome is an autoimmune disorder characterized by vascular thromboses and pregnancy morbidity associated with antiphospholipid antibodies: lupus anticoagulant, IgG or IgM anticardiolipin or anti-beta 2-glycoprotein I. The kidney is one of the major target organs in antiphospholipid syndrome (APS). However, beyond the known involvement of the kidney in primary and associated APS, we may be observing a new form of APS within the context of renal failure. This review describes the classical kidney manifestations of APS and provides new considerations to be taken into account.

Clinical significance and correlations between anti-β2 glycoprotein I IgA assays in antiphospholipid syndrome and/or systemic lupus erythematosus

BACKGROUND

The objective of this investigation was to examine the clinical significance of IgA anti-β2 glycoprotein I (anti-β2GPI) antibodies and the inter-assay relationships between kits for their determination.

METHODS

Serum samples from 269 patients with clinical diagnoses of systemic lupus erythematosus (SLE) and/or antiphospholipid syndrome (APS), individuals positive for antiphospholipid antibodies (aPL) with or without APS or SLE, and 182 controls were tested for anti-β2GPI IgA antibodies using kits from four manufacturers.

RESULTS

The positivity rates for the different IgA anti-β2GPI antibody kits varied in the disease groups; 7.8-14.7% (SLE only), 12.0-15.7% (SLE and APS/aPL), 14.7-58.8% (APS only), and 17.4-52.2% (aPL only). Kappa agreements between any 2 kits within disease groups were also variable and ranged from 0.25-1.00 (SLE), 0.18-1.00 (SLE and APS/aPL), 0.22-0.94 (APS only), and 0.32-0.91 (aPL only). Univariate analyses also showed variable relative risks for specific APS clinical manifestations with the different kits evaluated. Overall, diagnostic and predictive values for IgA anti-β2GPI antibodies are kit-dependent; therefore results are not interchangeable. While all 4 kits seem able to predict venous thrombosis tolerably well, there was a variable performance in predicting pregnancy related morbidity.

CONCLUSIONS

Efforts to standardize these assays are highly needed prior to their formal adoption in routine clinical evaluation.

The Significance of Anti-Beta-2-Glycoprotein I Antibodies in Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is a thrombophilic disorder that classically presents with vascular thrombosis and/or obstetric complications. APS is associated with antiphospholipid antibodies: a heterogeneous group of autoantibodies that are directed against membrane phospholipids in complex with phospholipid-binding proteins. Beta-2-glycoprotein I (B2GPI) binds anionic phospholipids and is considered to be the predominant antigen in APS and antibodies against B2GPI (anti-B2GPI) are recognised in the laboratory criteria for APS diagnosis. This review focuses on the part played by anti-B2GPI in the pathogenesis of APS, their associations with different clinical phenotypes of the disorder and new avenues for refining the diagnostic potential of anti-B2GPI testing.

Measuring IgA Anti-β2-Glycoprotein I and IgG/IgA Anti-Domain I Antibodies Adds Value to Current Serological Assays for the Antiphospholipid Syndrome

Introduction

Currently available clinical assays to detect antiphospholipid antibodies (aPL) test for IgG and IgM antibodies to cardiolipin (aCL) and β₂-glycoprotein I (aβ₂GPI). It has been suggested that testing for IgA aPL and for antibodies to Domain I (DI), which carries the key antigenic epitopes of β₂GPI, could add value to these current tests. We performed an observational, multicenter cohort study to evaluate the utility of IgG, IgM and IgA assays to each of CL, β₂GPI and DI in APS.

Methods

Serum from 230 patients with APS (n = 111), SLE but not APS (n = 119), and 200 healthy controls were tested for IgG, IgM and IgA aCL, aβ₂GPI and aDI activity. Patients with APS were further classified into thrombotic or obstetric APS. Logistic regression and receiver operator characteristic analyses were employed to compare results from the nine different assays.

Results

All assays displayed good specificity for APS; IgG aCL and IgG aβ₂GPI assays however, had the highest sensitivity. Testing positive for IgA aβ₂GPI resulted in a higher hazard ratio for APS compared to IgM aβ₂GPI. Positive IgG, IgM or IgA aDI were all associated with APS, and in subjects positive for aCL and/or aβ₂GPI, the presence of aDI raised the hazard ratio for APS by 3–5 fold. IgG aCL, aβ₂GPI, aDI and IgA aDI were associated with thrombotic but not obstetric complications in patients with APS.

Conclusion

Measuring IgG aDI and IgA aβ₂GPI and aDI may be useful in the management of patients with APS, particularly thrombotic APS.

Laboratory testing for antiphospholipid syndrome

This is a practical report on laboratory tests for the diagnosis of antiphospholipid syndrome (APS). After a general definition of APS, this study deals with appropriateness and timing in requesting the determination of antiphospholipid (aPL) antibodies. Lupus anticoagulant (LAC), anticardiolipin (aCL), and anti β2-glycoprotein I (aβGPI) are the mandatory tests to be performed, while other tests are not yet validated for clinical use. Interpretation of results is an important discussed issue that implies a close liaison between clinical pathologists and clinicians. Finally, a personal definition of APS according to aPL antibody profile closes the manuscript.

Circulating Immune Complexes of IgA Bound to Beta 2 Glycoprotein are Strongly Associated with the Occurrence of Acute Thrombotic Events

Aim: Antiphospholipid syndrome (APS) is characterized by recurrent thrombosis and/or gestational morbidity in patients with antiphospholipid autoantibodies (aPL). Over recent years, IgA anti-beta2-glycoprotein I (B2GPI) antibodies (IgA aB2GPI) have reached similar clinical relevance as IgG or IgM isotypes. We recently described the presence of immune complexes of IgA bounded to B2GPI (B2A-CIC) in the blood of patients with antecedents of APS symptomalology. However, B2A-CIC's clinical associations with thrombotic events (TEV) have not been described yet.

Methods: A total of 145 individuals who were isolate positive for IgA aB2GPI were studied: 50 controls without any APS antecedent, 22 patients with recent TEV (Group-1), and 73 patients with antecedents of old TEV (Group-2).

Results: Mean B2A-CIC levels and prevalence in Group-1 were 29.6 ± 4.1 AU and 81.8%, respectively, and were significantly higher than those of Group-2 and controls (p < 0.001). In a multivariable analysis, positivity of B2A-CIC was an independent variable for acute thrombosis with a 22.7 odd ratio (confidence interval 5.1 –101.6, 95%, p < 0.001). Levels of B2A-CIC dropped significantly two months after the TEV. B2A-CIC positive patients had lower platelet levels than B2A-CIC-negative patients (p < 0.001) and more prevalence of thrombocytopenia (p < 0.019). Group-1 had no significant differences in C3 and C4 levels compared with other groups.

Conclusion: B2A-CIC is strongly associated with acute TEV. Patients who did not develop thrombosis and were B2A-CIC positive had lower platelet levels, which suggest a hypercoagulable state. This mechanism is unrelated to complement-fixing aPL. B2A-CIC could potentially select IgA aB2GPI-positive patients at risk of developing a thrombotic event.

Autoantibodies in SLE: Specificities, Isotypes and Receptors

Systemic Lupus Erythematosus (SLE) is characterized by a wide spectrum of auto-antibodies which recognize several cellular components. The production of these self-reactive antibodies fluctuates during the course of the disease and the involvement of different antibody-secreting cell populations are considered highly relevant for the disease pathogenesis. These cells are developed and stimulated through different ways leading to the secretion of a variety of isotypes, affinities and idiotypes. Each of them has a particular mechanism of action binding to a specific antigen and recognized by distinct receptors. The effector responses triggered lead to a chronic tissue inflammation. DsDNA autoantibodies are the most studied as well as the first in being characterized for its pathogenic role in Lupus nephritis. However, others are of growing interest since they have been associated with other organ-specific damage, such as anti-NMDAR antibodies in neuropsychiatric clinical manifestations or anti-β2GP1 antibodies in vascular symptomatology. In this review, we describe the different auto-antibodies reported to be involved in SLE. How autoantibody isotypes and affinity-binding to their antigen might result in different pathogenic responses is also discussed.

Clinical characterization of antiphospholipid syndrome by detection of IgG antibodies against β2 -glycoprotein i domain 1 and domain 4/5: ratio of anti-domain 1 to anti-domain 4/5 as a useful new biomarker for antiphospholipid syndrome

OBJECTIVE

It has been suggested that only antibodies against domain 1 (D1) of β2 -glycoprotein I (β2 GPI) are pathogenic and diagnostic. The role of antibodies against other β2 GPI domains is still debated. This study was undertaken to evaluate the clinical relevance of domain specificity profiling of anti-β2 GPI IgG antibodies in antiphospholipid syndrome (APS) patients and in control groups of patients with systemic autoimmune rheumatic diseases and in asymptomatic antiphospholipid antibody (aPL) carriers.

METHODS

We evaluated 159 subjects with persistently positive, medium or high-titer anti-β2 GPI IgG, including 56 patients with thrombotic (obstetric or nonobstetric) primary APS, 31 women with obstetric primary APS, 42 aPL-positive patients with systemic autoimmune rheumatic diseases, and 30 asymptomatic aPL carriers. One hundred healthy donors were included. Anti-β2 GPI D1 and D4/5 IgG were tested on research enzyme-linked immunosorbent assays containing recombinant β2 GPI domains.

RESULTS

As compared to other groups, aPL carriers displayed higher frequency/titer of anti-D4/5 IgG. Unlike anti-D4/5, anti-D1 IgG antibodies were more frequent and at higher titer in triple than in single or double aPL-positive subjects. An anti-D1 to anti-D4/5 ratio of ≥1.5 was predictive of systemic autoimmunity (odds ratio 3.25 [95% confidence interval 1.45-7.49], P = 0.005). Neither anti-D1 nor anti-D4/5 antibodies were associated with APS clinical criteria.

CONCLUSION

Anti-D1 IgG is the preferential specificity not only in vascular and obstetric primary APS, but also in patients with systemic autoimmune rheumatic disease with no clinical features of APS. Conversely, aPL carriers do not have a polarized profile toward D1. Combined testing for anti-β2 GPI IgG with different domain specificity allows a more accurate aPL profiling, with polarization toward anti-D1 IgG as a possible fingerprint of systemic autoimmunity.

Differential assay reactivity of immunglobulin A anti-ß2 glycoprotein I antibodies: implications for the clinical interpretation of antiphospholipid antibody testing

OBJECTIVE

The routine measurement of IgA anticardiolipin (aCL) and IgA anti-β₂ glycoprotein I (anti-β₂ GPI) antibodies remain controversial despite several studies demonstrating an association with thromboembolic disease in patients with systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS). This controversy may be a contributing factor for the current under use of IgA antiphospholipid antibodies. We aimed to investigate the nature of discrepant IgA anti-β₂ GPI reactivity to help define the diagnostic value of IgA antiphospholipid antibodies.

MATERIAL AND METHODS

Four sera selected from SLE/APS patients and positive for antiphospholipid antibodies but having discrepant IgA anti-β₂ GPI reactivity on two commercial assays were studied. IgA antibodies were affinity purified to investigate anti-β₂ GPI reactivity. Column wash through and eluent fractions were tested on both IgA anti-β₂ GPI assays. Results were normalized to total protein. Assay conjugates and standards from the discrepant assays were interchanged.

RESULTS

The diseased samples were strongly positive in one assay [144-388 IgA antiphospholipid (APL) units] and negative or weakly positive in another assay (9.9-53 APL units). IgA eluents from IgA anti-β₂ GPI positive samples reacted 10 times stronger on the reactive assay. When normalized to protein content, the eluents showed no cross-reactivity for IgG or IgM anti-β₂ GPI antibodies, confirming IgA isotype specificity. Conjugate interchange confirmed that both assays bound IgA anti-β₂ GPI antibodies, but the anti-IgA conjugate from the reactive assay was 4 times stronger, suggesting that its ability to detect IgA anti-β₂ GPI antibodies was partially dependent on the anti-IgA conjugate and calibration.

CONCLUSION

These results confirm not only the presence of IgA anti-β₂ GPI antibodies in the selected patient samples but also highlight an IgA conjugate issue for the unreactive assay, causing an underestimation of IgA anti-β₂ GPI. This finding may assist in the ongoing standardization efforts of APS antibody testing. In addition, conclusions from published clinical studies may need to be revised as some assays may understate IgA significance.

The role of the gut microbiota in the pathogenesis of antiphospholipid syndrome

Infectious triggers are associated with the induction of transient antiphospholipid antibodies. One therefore wonders if microbes that permanently colonize us play a role in the pathogenesis of antiphospholipid syndrome (APS). The microbiota represents the collection of all microorganisms colonizing humans and is necessary for normal host physiology. The microbiota, however, is a constant stress on the immune system, which is tasked with recognizing and eliminating pathogenic microbes while tolerating commensal populations. A growing body of literature supports a critical role for the commensal-immune axis in the development of autoimmunity against colonized barriers (e.g., gut or skin) and sterile organs (e.g., pancreas or joints). Whether these interactions affect the development and sustainment of autoreactive CD4(+) T cells and pathogenic autoantibodies in APS is unknown. This review provides an overview of the current understanding of the commensal-immune axis in autoimmunity with a focus on the potential relevance to APS. Additionally, we discuss emerging findings supporting the involvement of the gut microbiota in a spontaneous model of APS, the (NZW × BXSB)F1 hybrid, and formalize hypotheses to explain how interactions between the immune system and the microbiota may influence human APS etiopathogenesis.

IgA anticardiolipin and IgA anti-β2 glycoprotein I antibody positivity determined by fluorescence enzyme immunoassay in primary antiphospholipid syndrome

BACKGROUND

Primary antiphospholipid syndrome (PAPS) is an autoimmune disease characterized by thrombosis and/or pregnancy morbidity as well as blood antiphospholipid (aPL) antibodies such as anticardiolipin (aCL), anti-β2 glycoprotein I (anti-β2GPI) antibodies of the IgG/IgM isotype and lupus anticoagulant (LA). The clinical significance of aCL and anti-β2GPI antibodies of the IgA isotype in PAPS is still a controversial issue.

METHODS

Sera and plasma were collected from 84 PAPS patients (54 with thrombosis and/or pregnancy morbidity and 30 with pregnancy morbidity alone), 66 seronegative patients (subjects with clinical manifestations of PAPS although with negative results on conventional antiphospholipid antibody testing), and 78 healthy blood donors. IgA aCL and IgA anti-β2GPI were determined using fluorescence enzyme immunoassay (FEIA), (EliATM, Phadia AB, Uppsala, Sweden). For comparison purposes, the sera were also tested for IgG/IgM aCL/anti-β2GPI antibodies using the same immunoassay method. LA was assayed following internationally accepted guidelines.

RESULTS

Present respectively in 19% and 50% of the PAPS patients studied, IgA aCL and IgA anti-β2GPI antibody frequencies were both statistically significant (p=0.001 and p<0.001, respectively). The mean titers of both IgA aCL and IgA anti-β2GPI antibodies were higher in the thrombotic patients, but only the latter were significantly associated with thrombosis. Isolated IgA anti-β2GPI antibody positivity was significantly prevalent (p=0.04) in seven (10.6%) of the seronegative patients.

CONCLUSIONS

Positivity to IgA anti-β2GPI antibody detected using FEIA was found to be clinically relevant in PAPS patients. Moreover the prevalence of isolated IgA anti-β2GPI antibody positivity was significant in the seronegative patients.

Role of autoantibody testing

Autoantibodies are the serological hallmark of autoimmune disease. Though their pathogenic role is debatable, they play an important role in the management of a patient with rheumatic disease. However, due to their presence in the general population as well as in multiple autoimmune diseases, the presence of an autoantibody alone does not make a diagnosis; the result has to be interpreted along with clinical findings. Similarly, the absence of autoantibody does not exclude a disease. The common autoantibodies used in clinical practice include rheumatoid factor, anti-CCP antibodies, antinuclear antibodies (ANAs), anti-neutrophil cytoplasmic antibodies (ANCA) and anti-phospholipid antibodies. Once an autoantibody to a broad antigen is detected in a patient, sub-specificity analysis can improve the utility of the antibody. Autoantibodies are detected in the serum using different assays and results of which can vary; thus, it is important for a clinician to know the method used, its sensitivity and specificity to help in the proper interpretation of the laboratory results. This review will address these issues.

Detection of circulating immune complexes of human IgA and beta 2 glycoprotein I in patients with antiphospholipid syndrome symptomatology

BACKGROUND

Patients with antiphospholipid syndrome (APS) have a hypercoagulable condition associated with the presence of antiphospholipid autoantibodies (aPL). Consensus antibodies for diagnosis are lupus anticoagulant, anti-beta2 glycoprotein I (B2GPI) and anticardiolipin (IgG or IgM). Circulating immunocomplexes (CIC) of B2GPI associated with IgM or IgG were reported. Isolated IgA aB2GPI antibodies have achieved high diagnostic value although specific CIC of B2GPI bounded to IgA (B2A-CIC) has still not been described. CIC detection assays are mainly based on interaction with complement and are not appropriate to detect B2A-CIC because IgA does not fix complement using the classical pathway.

PATIENTS AND METHODS

Sera from healthy blood donors (N= 247) and from patients with thrombosis background and isolate positive for IgA aB2GPI (N = 68) were studied in a case-control study. Two methods were applied, these being a capture ELISA to quantify specific B2A-CIC and quantification of total IgA anti-B2GPI after dissociating CIC.

RESULTS

B2A-CIC values in APS-patients were 19.27 ± 2.6 AU vs 6.1 ± 0.4 AU in blood donors (p < 0.001). There were 36.4% B2A-CIC positive patients (cutoff 21 AU) versus 5.5% in blood donors (p < 0.001). Dissociated IgA aB2GPI levels (total IgA aB2GPI) were 146.8 ± 10.8 IU/mL in patients vs. 22.4 IU/mL in controls (p < 0.001). B2A-CIC was independent of B2GPI and autoantibodies IgA aB2GPI serum levels.

CONCLUSION

B2A-CIC can be identified and quantified in an easy and reproducible manner using two complement-independent methods. The use of these tests in prospective studies will allow better understanding of the prognosis and outcome of patients.

The coexistence of antiphospholipid syndrome and systemic lupus erythematosus in Colombians

OBJECTIVES

To examine the prevalence and associated factors related to the coexistence of antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE) in a cohort of Colombian patients with SLE, and to discuss the coexistence of APS with other autoimmune diseases (ADs).

METHOD

A total of 376 patients with SLE were assessed for the presence of the following: 1) confirmed APS; 2) positivity for antiphospholipid (aPL) antibodies without a prior thromboembolic nor obstetric event; and 3) SLE patients without APS nor positivity for aPL antibodies. Comparisons between groups 1 and 3 were evaluated by bivariate and multivariate analysis.

RESULTS

Although the prevalence of aPL antibodies was 54%, APS was present in just 9.3% of SLE patients. In our series, besides cardiovascular disease (AOR 3.38, 95% CI 1.11-10.96, p = 0.035), pulmonary involvement (AOR 5.06, 95% CI 1.56-16.74, p = 0.007) and positivity for rheumatoid factor (AOR 4.68, 95%IC 1.63-14.98, p = 0.006) were factors significantly associated with APS-SLE. APS also may coexist with rheumatoid arthritis, Sjögren's syndrome, autoimmune thyroid diseases, systemic sclerosis, systemic vasculitis, dermatopolymyositis, primary biliary cirrhosis and autoimmune hepatitis.

CONCLUSIONS

APS is a systemic AD that may coexist with other ADs, the most common being SLE. Awareness of this polyautoimmunity should be addressed promptly to establish strategies for controlling modifiable risk factors in those patients.

Association of early kidney allograft failure with preformed IgA antibodies to β2-glycoprotein I

In the current immunosuppressive therapy era, vessel thrombosis is the most common cause of early graft loss after renal transplantation. The prevalence of IgA anti-β2-glycoprotein I antibodies (IgA-aB2GPI-ab) in patients on dialysis is elevated (>30%), and these antibodies correlate with mortality and cardiovascular morbidity. To evaluate the effect of IgA-aB2GPI-ab in patients with transplants, we followed all patients transplanted from 2000 to 2002 in the Hospital 12 de Octubre prospectively for 10 years. Presence of IgA-aB2GPI-ab in pretransplant serum was examined retrospectively. Of 269 patients, 89 patients were positive for IgA-aB2GPI-ab (33%; group 1), and the remaining patients were negative (67%; group 2). Graft loss at 6 months post-transplant was significantly higher in group 1 (10 of 89 versus 3 of 180 patients in group 2; P=0.002). The most frequent cause of graft loss was thrombosis of the vessels, which was observed only in group 1 (8 of 10 versus 0 of 3 patients in group 2; P=0.04). Multivariate analysis showed that the presence of IgA-aB2GPI-ab was an independent risk factor for early graft loss (P=0.04) and delayed graft function (P=0.04). There were no significant differences regarding patient survival between the two groups. Graft survival was similar in both groups after 6 months. In conclusion, patients with pretransplant IgA-aB2GPI-ab have a high risk of early graft loss caused by thrombosis and a high risk of delayed graft function. Therefore, pretransplant IgA-aB2GPI-ab may have a detrimental effect on early clinical outcomes after renal transplantation.

Antiphospholipid antibodies in women undergoing in vitro fertilization treatment: clinical value of IgA anti-β2glycoprotein I antibodies determination

Implantation failure could be related to antiphospholipid antibodies (aPL). We retrospectively analyzed the usefulness of aPL determination in women undergoing IVF. Conventional aPL of the antiphospholipid syndrome, lupus anticoagulant (LA), anticardiolipin antibodies (aCL), anti-β2glycoprotein I (aβ2GPI) antibodies, and IgG and IgM isotypes as well as IgA isotype were analyzed in women presenting with at least two implantation failures after in vitro fertilization (IVF). In a population of 40 IVF patients, a total prevalence of 20% (8/40) of aPL was found, significantly different from that of the control population (100 healthy blood donors, P < 0.0005). Among the panels of aPL tested, aβ2GPI IgA antibodies were the most prevalent (62.5% 5/8), significantly higher in IVF patients (12.5%, 5/40) than in controls (1%, 1/100) (P = 0.01). No difference according to the numbers of IVF attempts and success of embryo implantation was found between aPL positive and negative IVF patients. In contrast, no accomplished pregnancy with full-term live birth was observed in aPL positive IVF patients. Altogether our data led us to propose aPL assessment, in particular aβ2GPI IgA antibodies, in support of IVF treated women. In a perspective way, an early aPL detection could be the basis for defining novel therapeutic strategy.

14th International Congress on Antiphospholipid Antibodies Task Force. Report on antiphospholipid syndrome laboratory diagnostics and trends

Current classification criteria for definite Antiphospholipid Syndrome (APS) require the use of three laboratory assays to detect antiphospholipid antibodies (aCL, anti-β2GPI and LA) in the presence of at least one of the two major clinical manifestations (i.e. thrombosis or pregnancy morbidity) of the syndrome. However, several other autoantibodies shown to be directed to other proteins or their complex with phospholipids have been proposed to be relevant to APS but their clinical utility and their diagnostic value remains elusive. This report summarizes the findings, conclusions and recommendations of the "APS Task Force 3-Laboratory Diagnostics and Trends" meeting that took place during the 14th International Congress on Antiphospholipid Antibodies (APLA 2013, September 18-21, Rio de Janeiro, RJ, Brazil).

High expression of beta2-glycoprotein I is associated significantly with the earliest stages of hepatitis B virus infection

Human beta2-glycoprotein I (beta2-GPI) binds to recombinant hepatitis B surface antigen (rHBsAg) and can bind specifically to annexin II, which is located on the cell membrane of human hepatoma SMMC-7721 cells. Viral envelope proteins are essential for mediating cellular entry. The aim of this study was to investigate the role of beta2-GPI in the early stages of hepatitis B virus (HBV) infection. Western blot and qRT-PCR analyses revealed that beta2-GPI expression was upregulated in HepG2.2.15 cells at both the mRNA and protein level and was almost non-existent in 293T and CHO cells. Furthermore, annexin II was expressed at lower levels in HepG2.2.15 cells compared to L02, HepG2, and SMMC-7721 cells. Additionally, ELISA analyses demonstrated that beta2-GPI enhanced the ability of HBsAg to bind to cell surfaces, and there was differential adhesion to L02, HepG2, HepG2.2.15, and 293T cells. Western blot and ELISA were then performed to assess the effects of HBV and the HBsAg domain on beta2-GPI expression in co-transfected 293T cells. This study revealed that HBV and the large HBV envelope protein increased beta2-GPI expression. Further investigation indicated that beta2-GPI colocalized with HBsAg in the cytosol of HepG2.2.15 cells, with sodium taurocholate co-transporting polypeptide (NTCP) on the cell membrane in NTCP-complemented HepG2 cells, and with annexin II in the cytosol of HepG2 and HepG2.2.15 cells. These data suggest that high expression of beta2-GPI enhances HBsAg binding to cell surfaces, thus contributing to virus particle transfer to the NTCP receptor and interaction with annexin II for viral membrane fusion.

Renal transplantation dramatically reduces IgA anti-beta-2-glycoprotein I antibodies in patients with endstage renal disease

IgA anti-beta-2-glycoprotein I (aB2GPI) antibodies have been related to vascular pathology in the general population and mainly in hemodialyzed patients (prevalence 33%) in whom an elevated incidence of thrombosis and mortality is found. In this paper we have studied the presence of IgA aB2GPI antibodies at pretransplant and their evolution after transplantation with a cross-sectional-based follow-up study of a cohort of 288 endstage renal disease (ESRD) patients treated with kidney transplantation. Pretransplant IgA aB2GPI levels were elevated 31.7 ± 4.2 U/mL without differences in age or type of dialysis. Patients with different etiologies of ESRD showed higher levels of IgA aB2GPI than blood donors, except the groups of non-IgA glomerular disease and systemic erythematosus lupus, whose nonsignificant differences were observed. IgA aB2GPI antibodies dropped immediately after transplantation (10.7 ± 1.0 U/mL, P < 0.0001), coinciding with a high degree of immunosuppression, and remained significantly lower than that observed in pretransplant status. Prevalence of patients with elevated antibodies was also less in transplanted patients (8.9% versus 30.4%, P < 0.0001). Among, positivity for IgA aB2GPI was higher than in patients who had received their first transplant that those were retransplanted. This finding could have important clinical implications and can suggest new therapeutic strategies in patients with IgA aB2GPI antibodies.

Isolated IgA anti- β2 glycoprotein I antibodies in patients with clinical criteria for antiphospholipid syndrome

Seronegative antiphospholipid syndrome (SNAPS) is an autoimmune disease present in patients with clinical manifestations highly suggestive of Antiphospholipid Syndrome (APS) but with persistently negative consensus antiphospholipid antibodies (a-PL). IgA anti-β2 Glycoprotein I (aB2-GPI) antibodies are associated with APS. However, they are not currently considered to be laboratory criteria due to the heterogeneity of published works and the use of poor standardized diagnostic systems. We have aimed to assess aPL antibodies in a group of patients with clinical manifestations of APS (C-APS) to evaluate the importance of the presence of IgA aB2GPI antibodies in APS and its relation with other aPL antibodies. Only 14% of patients with C-APS were positive for any consensus antibody, whereas the presence of isolated IgA aB2GPI antibodies was found in 22% of C-APS patients. In patients with arterial thrombosis IgA aB2GPI, antibodies were the only aPL antibodies present. Serologic profile in primary APS (PAPS) is different from systemic autoimmune disorders associated APS (SAD-APS). IgA aB2GPI antibodies are more prevalent in PAPS and IgG aB2GPI antibodies are predominant in SAD-APS. The analysis of IgA aB2GPI antibodies in patients with clinical manifestations of PAPS might avoid underdiagnosed patients and provide a better diagnosis in patients with SAD-APS. Laboratory consensus criteria might consider including analysis of IgA aB2GPI for APS diagnosis.

Antiphospholipid syndrome in 2014: more clinical manifestations, novel pathogenic players and emerging biomarkers

The clinical spectrum of the anti-phospholipid syndrome (APS) is not limited to vascular thrombosis or miscarriages but includes additional manifestations that cannot be explained solely by a thrombophilic state. Anti-cardiolipin, anti-beta₂ glycoprotein I (anti-β₂GPI) and lupus anticoagulant (LA) assays are not only the formal diagnostic and classification laboratory tools but also parameters to stratify the risk to develop the clinical manifestations of the syndrome. In particular, anti-β₂GPI antibodies reacting with an immunodominant epitope on domain I of the molecule were reported as the prevalent specificity in APS patients, correlating with a more aggressive clinical picture. Several laboratory assays to improve the diagnostic and predictive power of the standard tests have been proposed. Plates coated with the phosphatidylserine-prothrombin complex for detecting antibodies represent a promising laboratory tool correlating with LA and with clinical manifestations. Anti-phospholipid antibodies can be found in patients with full-blown APS, in those with thrombotic events or obstetric complications only or in asymptomatic carriers. An inflammatory second hit is required to increase the presence of β₂GPI in vascular tissues, eventually triggering thrombosis. Post-transcriptional modifications of circulating β₂GPI, different epitope specificities or diverse anti-β₂GPI antibody-induced cell signaling have all been suggested to affect the clinical manifestations and/or to modulate their occurrence.

Heterogeneity between diagnostic tests for IgA anti-beta2 glycoprotein I: explaining the controversy in studies of association with vascular pathology

IgA antibeta 2 Glycoprotein I (β2GPI) antibodies test can identify some patients with antiphospholipid syndrome (APS) that are negative for other isotypes. Controversy exists because some studies have reported a strong association of these antibodies with vascular disease, while others have not confirmed this observation. Our hypothesis is that these contradictory results may be due to differences among commercial diagnostic kits. To answer this question, we have compared the results obtained with several of the most commonly used commercial IgA anti β2GPI antibodies (aβ2GPI) diagnostic assays on specimens from individuals suspected of having APS. Sera from 69 patients (37 positive and 32 negative for IgA aβ2GPI) were analyzed with seven different commercial ELISA kits for IgA aβ2GPI, following instructions and cutoffs provided by the manufacturer. Our results showed important differences in the sensitivity and specificity of the different assays. Two of the seven kits tested had a sensitivity level below 65% for IgA aβ2GPI, and three showed levels of specificity lower than 80%. Some commercial kits to detect IgA aβ2GPI are suboptimal. Variability between kits may account for the discrepancy in results obtained and for the lack of consensus concerning their clinical significance. It is important that the scientific community work to standardize assay performance so that the true clinical significance of this important clinical marker can be clearly established.