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

Embolism from a left ventricular myxoma presenting with acute limb ischaemia

Acute limb ischaemia (ALI) secondary to cardiac myxoma is uncommon. Embolic myxoma should be considered a differential diagnosis in young patients with ALI who do not have apparent cardiovascular risk factors. A multidisciplinary approach and comprehensive care can improve outcomes and optimise the collaborative treatment of ALI. Early referral to a hospital that can provide specialised treatment for ALI helps prevent significant tissue loss and surgical complications, such as amputation.A man in his 20s presented with bilateral ALI of both lower extremities, and an arterial duplex scan revealed a thrombus occluding all arterial segments of the bilateral lower extremities. An intracardiac mass adherent to the apical and anterior interventricular septum on two-dimensional echocardiography suggested a complex myxoma. The patient was diagnosed with ALI Rutherford category III, and bilateral hip disarticulation was performed. The patient was discharged with an anticoagulant.

SAMD1 attenuates antiphospholipid syndrome-induced pregnancy complications

OBJECTIVE

This study was intended to investigate the effect of SAMD1 on antiphospholipid syndrome (APS)-induced pregnancy complications in mice.

METHODS

The mRNA and protein expression of SAMD1 in APS patients and healthy controls was detected by qRT-PCR and western blot. Anti-B2 GPI and ACA levels were tested by ELISA, MMP-9, iNOS, ICAM-1 and MCP-1 mRNA and protein levels determined by qRT-PCR and western blot, cellular senescence detected by β-galactosidase staining, cell proliferation ability detected by CCK-8 assay, cell viability detected by trypan blue staining, cell mobility detected by Transwell, and cell angiogenesis ability detected by matrigel tube formation assay. An APS pregnant mouse model was constructed, and the embryo absorption rate was calculated.

RESULTS

SAMD1 expression was low in serum of APS patients, which was correlated with the history of thrombosis and the number of adverse pregnancies. Anti-B2 GPI and ACA levels were increased in APS. The expressions of MMP-9, iNOS, ICAM-1, and MCP-1 were also significantly upregulated in HUVECs treated with APS serum. APS promoted HUVEC senescence and inhibited cell proliferation, migration and angiogenesis. Overexpression of SAMD1 reversed the above results. Experiments on the APS pregnant mouse model confirmed that overexpression of SAMD1 reduced the rate of fetal loss.

CONCLUSION

SAMD1 may reduce APS-induced embryo loss by regulating cellular senescence, proliferation, migration, and angiogenesis.

Anti-β2-glycoprotein I and anti-phosphatidylserine/prothrombin antibodies interfere with cleavage of factor V(a) by activated protein C

BACKGROUND

The acquired thrombotic risk factor known as lupus anticoagulant (LA) interferes with laboratory clotting assays and can be caused by autoantibodies against β2-glycoprotein I (β2GPI) and prothrombin. LA is associated with activated protein C (APC) resistance, which might contribute to thrombotic risk in patients with antiphospholipid syndrome. How antibodies against β2GPI and prothrombin cause APC resistance is currently unclear.

OBJECTIVES

To investigate how anti-β2GPI and antiphosphatidylserine/prothrombin (PS/PT) antibodies induce APC resistance.

METHODS

The effects of anti-β2GPI and anti-PS/PT antibodies on APC resistance were studied in plasma (of patients with antiphospholipid syndrome) and with purified coagulation factors and antibodies.

RESULTS

APC resistance was observed in LA-positive patients with anti-β2GPI or anti-PS/PT antibodies and in normal plasma spiked with monoclonal anti-β2GPI or anti-PS/PT antibodies with LA activity. Analysis of factor (F)V cleavage patterns after APC incubation indicated that anti-β2GPI antibodies attenuated APC-mediated FV cleavage at R506 and R306. APC-mediated cleavage at R506 is required for FV cofactor activity during inactivation of FVIIIa. Assays with purified coagulation factors confirmed that anti-β2GPI antibodies interfered with the cofactor function of FV during FVIIIa inactivation but not with FVa inactivation. Anti-PS/PT antibodies attenuated APC-mediated FVa and FVIIIa inactivation. Analysis of FV(a) cleavage patterns after APC incubation indicated that anti-PS/PT antibodies interfere with APC-mediated cleavage of FV at positions R506 and R306.

CONCLUSION

Anti-β2GPI antibodies with LA activity contribute to a procoagulant state by causing APC resistance via interference with the cofactor function of FV during FVIIIa inactivation. LA-causing anti-PS/PT antibodies interfere with the anticoagulant function of APC by preventing FV(a) cleavage.

Oxidative Stress as a Regulatory Checkpoint in the Production of Antiphospholipid Autoantibodies: The Protective Role of NRF2 Pathway

Oxidative stress is a well-known hallmark of Antiphospholipid Antibody Syndrome (APS), a systemic autoimmune disease characterized by arterial and venous thrombosis and/or pregnancy morbidity. Oxidative stress may affect various signaling pathways and biological processes, promoting dysfunctional immune responses and inflammation, inducing apoptosis, deregulating autophagy and impairing mitochondrial function. The chronic oxidative stress and the dysregulation of the immune system leads to the loss of tolerance, which drives autoantibody production and inflammation with the development of endothelial dysfunction. In particular, anti-phospholipid antibodies (aPL), which target phospholipids and/or phospholipid binding proteins, mainly β-glycoprotein I (β-GPI), play a functional role in the cell signal transduction pathway(s), thus contributing to oxidative stress and thrombotic events. An oxidation-antioxidant imbalance may be detected in the blood of patients with APS as a reflection of disease progression. This review focuses on functional evidence highlighting the role of oxidative stress in the initiation and progression of APS. The protective role of food supplements and Nuclear Factor Erythroid 2-Related Factor 2 (NRF2) activators in APS patients will be summarized to point out the potential of these therapeutic approaches to reduce APS-related clinical complications.

An Antiphospholipid Antibody Profile as a Biomarker for Thrombophilia in Systemic Lupus Erythematosus

Despite recent advances in treatment and significant improvements in prognosis, thrombosis remains the major cause of death in systemic lupus erythematosus (SLE). Antiphospholipid antibodies (aPL) are the main triggers of thrombosis in patients with SLE, with a frequency of approximately 30-40%. Lupus anticoagulant, anticardiolipin, and anti-β2-glycoprotein I antibodies, which are included in the criteria for antiphospholipid syndrome, and 'non-criteria' aPL such as anti-phosphatidylserine/prothrombin complex antibodies, are risk factors for thrombosis in patients with SLE. Multiple positivity for aPL is also associated with an increased risk of thrombosis, and scores calculated from aPL profiles can predict the risk of developing thrombosis. Although there is insufficient evidence for treatment, aPL-positive SLE patients should/may be treated with anticoagulants and/or low-dose aspirin as appropriate. This review summarises the evidence on the clinical significance of the aPL profile as a biomarker of thrombophilia in patients with SLE.

SAMD1 attenuates antiphospholipid syndrome-induced vascular injury and pregnancy complications

OBJECTIVE

This study was intended to investigate the effect of SAMD1 on antiphospholipid syndrome (APS)-induced vascular injury in human umbilical vein endothelial cells (HUVECs) and pregnancy complications in mice.

METHODS

The expression of SAMD1 in APS patients and healthy controls was detected by quantitative real-time polymerase chain reaction (qRT-PCR). Anti-B₂ GPI and anticardiolipin antibody (ACA) levels were tested by enzyme-linked immunosorbent assay, MMP-9, iNOS, ICAM-1, and MCP-1 mRNA and protein levels determined by qRT-PCR and Western blot, cellular senescence detected by β-galactosidase staining, cell proliferation ability detected by CCK-8 assay, cell viability detected by trypan blue staining, cell mobility detected by Transwell, and cell angiogenesis ability detected by matrigel tube formation assay. An APS pregnant mouse model was constructed, and the embryo absorption rate was calculated.

RESULTS

SAMD1 expression was low in serum of APS patients, which was correlated with the history of thrombosis and the number of adverse pregnancies. Anti-B₂ GPI and ACA levels were increased in APS. The expressions of MMP-9, iNOS, ICAM-1, and MCP-1 were also significantly upregulated in HUVECs treated with APS serum. APS promoted HUVEC senescence and inhibited cell proliferation, migration, and angiogenesis. Overexpression of SAMD1 reversed the above results. Experiments on the APS pregnant mouse model confirmed that overexpression of SAMD1 reduced the rate of fetal loss.

CONCLUSION

SAMD1 may reduce APS-induced vascular injury and embryo loss by regulating cellular senescence, proliferation, migration, and angiogenesis.

Seronegative autoimmune diseases: A challenging diagnosis

Autoimmune diseases (AID) are increasingly prevalent conditions which comprise more than 100 distinct clinical entities that are responsible for a great disease burden worldwide. The early recognition of these diseases is key for preventing their complications and for tailoring proper management. In most cases, autoantibodies, regardless of their potential pathogenetic role, can be detected in the serum of patients with AID, helping clinicians in making a definitive diagnosis and allowing screening strategies for early -and sometimes pre-clinical- diagnosis. Despite their undoubted crucial role, in a minority of cases, patients with AID may not show any autoantibody, a condition that is referred to as seronegative AID. Suboptimal accuracy of the available laboratory tests, antibody absorption, immunosuppressive therapy, immunodeficiencies, antigen exhaustion, and immunosenescence are the main possible determinants of seronegative AID. Indeed, in seronegative AID, the diagnosis is more challenging and must rely on clinical features and on other available tests, often including histopathological evaluation and radiological diagnostic tests. In this review, we critically dissect, in a narrative fashion, the possible causes of seronegativity, as well as the diagnostic and management implications, in several AID including autoimmune gastritis, celiac disease, autoimmune liver disease, rheumatoid arthritis, autoimmune encephalitis, myasthenia gravis, Sjögren's syndrome, antiphospholipid syndrome, and autoimmune thyroid diseases.

A systematic review of the association between anti-β-2 glycoprotein I antibodies and APS manifestations

Anti-β-2 glycoprotein I antibodies (anti-B2GPI) are often cited as the major pathogenically relevant antibody in antiphospholipid syndrome (APS), but it is unclear if there is clinical evidence to support this theory. We performed a systematic review to determine if immunoglobulin G anti-B2GPI positivity was independently associated with thrombotic and/or obstetric manifestations of APS. We searched MEDLINE, EMBASE, The Cochrane Library, and clinicaltrials.gov electronic databases through April 2020 for prospective studies that met prespecified design criteria. Of 4758 articles identified through computer-assisted search, 4 studies examining obstetric outcomes and 2 studies examining thrombotic outcomes were included for qualitative assessment. The presence of anti-B2GPI had only a weak independent association with thrombosis and was, at best, inconsistently associated with obstetric complications. A quantitative assessment could not be performed because of study heterogeneity. The overall quality of the evidence was very low. Although anti-B2GPI are commonly thought to mediate APS manifestations, clinical evidence is lacking with very low-quality data to support a weak association with thrombosis.

Major complications of dural venous sinus stenting for idiopathic intracranial hypertension: case series and management considerations

BACKGROUND

Venous sinus stenting (VSS) is a safe, effective, and increasingly popular treatment option for selected patients with idiopathic intracranial hypertension (IIH). Serious complications associated with VSS are rarely reported.

METHODS

Serious complications after VSS were identified retrospectively from multicenter databases. The cases are presented and management strategies are discussed.

RESULTS

Six major acute and chronic complications after VSS were selected from a total of 811 VSS procedures and 1466 venograms for IIH. These included an acute subdural hematoma from venous extravasation, cases of both intraprocedural and delayed stent thrombosis, an ultimately fatal cerebellar hemorrhage resulting in acute obstructive hydrocephalus, venous microcatheter perforation during venography and manometry, and a patient who developed subarachnoid hemorrhage and subdural hematoma after cerebellar cortical vein perforation. The six cases are reviewed and learning points regarding complication avoidance and management are presented.

CONCLUSION

We report on six rare, major complications after VSS for IIH. Familiarity with these potential complications and appropriate timely management may allow for good clinical outcomes.

Development of a certified reference material for anti-β2-glycoprotein I IgG - commutability studies

Objectives

In this paper, we describe the steps followed for the development of a certified reference material for immunoglobulin G antibodies against β2-glycoprotein I (also known as apolipoprotein H). These steps include processing of the material, commutability, the impact of dilution, the appropriate reconstitution conditions, homogeneity and stability during transport and storage.

Methods

We analysed 69 clinical samples from patients suffering from antiphospholipid syndrome with several commercial enzyme-linked immunosorbent assays (ELISA) purchased from in vitro diagnostic manufacturers.

Results

Analysis of the results indicated that the candidate reference material can be safely freeze-dried, and that the user should carefully follow the reconstitution instructions as small changes in e.g. temperature may have unwanted effects. The statistical analysis of the commutability studies indicated that the analytical response of the reference material upon dilution is similar to that of clinical samples, and that correlation between results may differ from assay to assay. Finally yet importantly, the presented and developed candidate reference material is commutable for most assays tested, homogeneous and stable.

Conclusions

Immunoglobulin G antibodies against β2-glycoprotein I are associated with a higher risk of thrombosis and pregnancy complications. Their measurement is essential for the diagnosis and monitoring of antiphospholipid syndrome. These antibodies are detected by specific immunoassays, routinely used in clinical diagnostics, but various of these methods show enormous variability, in part due to the lack of a reference material.

Seronegative antiphospholipid syndrome: refining the value of "non-criteria" antibodies for diagnosis and clinical management

Antiphospholipid syndrome (APS) is a systemic autoimmune disease characterized by arterial and venous thrombotic manifestations and/or pregnancy-related complications in patients with persistently high antiphospholipid antibodies (aPL), the most common being represented by anticardiolipin antibodies (aCL), anti-beta 2 glycoprotein-I (aβ2GPI), and lupus anticoagulant (LAC). A growing number of studies have showed that, in some cases, patients may present with clinical features of APS but with temporary positive or persistently negative titers of aPL. For these patients, the definition of seronegative APS (SN-APS) has been proposed. Nevertheless, the negativity to classic aPL criteria does not imply that other antibodies may be present or involved in the onset of thrombosis. The diagnosis of SN-APS is usually made by exclusion, but its recognition is important to adopt the most appropriate anti-thrombotic strategy to reduce the rate of recurrences. This research is in continuous development as the clinical relevance of these antibodies is far from being completely clarified. The most studied antibodies are those against phosphatidylethanolamine, phosphatidic acid, phosphatidylserine, phosphatidylinositol, vimentin/cardiolipin complex, and annexin A5. Moreover, the assays to measure the levels of these antibodies have not yet been standardized. In this review, we will summarize the evidence on the most studied non-criteria aPL, their potential clinical relevance, and the antithrombotic therapeutic strategies available in the setting of APS and SN-APS.

The anti-thrombotic effects of vitamin D and their possible relationship with antiphospholipid syndrome

The importance of the immunomodulatory effects of vitamin D has recently been associated with autoimmune and chronic inflammatory diseases. Vitamin D deficiency has been linked to the development of autoimmune conditions. Antiphospholipid syndrome is an autoimmune disease characterized by thrombotic events and obstetric complications in patients with antiphospholipid antibodies. Current data show that patients with antiphospholipid syndrome have a high prevalence of vitamin D deficiency even without classic risk factors. Several studies have suggested vitamin D may have anti-thrombotic functions. In antiphospholipid syndrome, low vitamin D serum levels have been associated with thrombotic manifestations, suggesting a possible protective role of vitamin D in antiphospholipid syndrome. This literature review presents current evidence on the haemostatic functions of vitamin D and their possible relationship with the clinical manifestations of antiphospholipid syndrome.

The Wolf Hidden behind the Clots: Catastrophic Antiphospholipid Antibody Syndrome

Catastrophic antiphospholipid syndrome (CAPS) is a rare but highly fatal clinical syndrome that occurs in up to 1% of patients with antiphospholipid syndrome (APS). The diagnosis of CAPS is often delayed because its presentation with multiple organ thromboses can be confused with other thrombotic microangiopathies and severe sepsis. We report a case of CAPS in a patient with APS and systemic lupus erythematosus (SLE) presenting with thrombotic storm precipitated by trauma, cytomegalovirus (CMV) infection, and noncompliance with anticoagulation therapy. Our case reflects the "two-hit hypothesis" of APS in which the presence of antiphospholipid antibodies (first hit) increases the thrombophilic risk, and thromboses take place in the presence of another thrombophilic condition such as CMV infection in our case. In this case review, we discuss the diagnostic challenges and management of CAPS. In clinical practice, we aim to stress the importance of thorough evaluation and management of precipitating events such as infections in addition to timely diagnosis and treatment of this catastrophic clinical entity.

Standardization of autoimmune testing – is it feasible?

Correct measurement of autoantibodies is essential for the diagnosis of autoimmune diseases. However, due to the variability of autoantibody results and the heterogeneity of testing, wrong diagnosis is a reality. For this and more reasons, harmonization of testing is of the outmost importance. In this review we have summarized the factors contributing to this variability. The ways with which the working group on harmonization of autoantibody testing of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) has been trying to tackle the issue with the production and correct use of certified reference materials (CRMs), is discussed. Finally the advantages and the limitations of the use of CRMs are presented.

Pretransplant IgA-Anti-Beta 2 Glycoprotein I Antibodies As a Predictor of Early Graft Thrombosis after Renal Transplantation in the Clinical Practice: A Multicenter and Prospective Study

Background

Graft thrombosis is a devastating complication after renal transplantation. We recently described the association of anti-beta-2-glycoprotein-I (IgA-ab2GP1) antibodies with early graft loss mainly caused by thrombosis in a monocenter study.

Methods

Multicenter prospective observational cohort study.

Setting and participants

Seven hundred forty patients from five hospitals of the Spanish Forum Renal Group transplanted from 2000 to 2002 were prospectively followed-up for 10 years.

Outcomes

Early graft loss and graft loss by thrombosis.

Measurements

The presence of IgA anti-B2GP1 antibodies in pretransplant serum was examined using the same methodology in all the patients.

Results

At transplantation, 288 patients were positive for IgA-B2GP1 (39%, Group-1) and the remaining were negative (Group-2). Graft loss at 6 months was higher in Group-1 (12.5 vs. 4.2% p < 0.001), vessel thrombosis being the most frequent cause of early graft loss, especially in Group-1 (6.9 vs. 0.4% p < 0.001). IgA-aB2GP1 was the most important independent risk factor for graft thrombosis (hazard ratio: 13.83; 95% CI: 3.17-60.27, p < 0.001). Furthermore, the, presence of IgA-aB2GP1 was associated with early graft loss and delayed graft function. At 10 years, survival figures were also lower in Group-1: graft survival was lower compared with Group-2 (60.4 vs. 76.8%, p < 0.001). Mortality was significantly higher in Group-1 (19.8 vs. 12.2%, p = 0.005).

Limitations

Patients were obtained during a 3-year period (1 January 2000-31 December 2002) and kidneys were only transplanted from brain-dead donors. Nowadays, the patients are older and the percentage of sensitized and retransplants is high.

Conclusion

In a prospective observational multicenter study, we were able to corroborate that pretransplant presence of IgA-aB2GP1 was the main risk factor for graft thrombosis and early graft loss. Therefore, a prospective study is needed to evaluate the efficacy and safety of prophylactic anticoagulation to avoid this severe complication.

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.

Current Controversies in Lupus Anticoagulant Detection

Antiphospholipid syndrome is an autoimmune, acquired thrombophilia diagnosed when vascular thrombosis or pregnancy morbidity are accompanied by persistent antiphospholipid antibodies. Lupus anticoagulants (LA) are one of the criteria antibodies but calibration plasmas are unavailable and they are detected by inference based on antibody behaviour in a medley of coagulation-based assays. Elevated screening tests suggest the presence of a LA, which is confirmed with mixing tests to evidence inhibition and confirmatory tests to demonstrate phospholipid-dependence. At least two screening tests of different principle must be used to account for antibody heterogeneity and controversy exists on whether assays, in addition to dilute Russell's viper venom time and activated partial thromboplastin time, should be employed. A variety of approaches to raw data manipulation and interpretation attract debate, as does inclusion or exclusion of mixing studies in circumstances where the presence of a LA is already evident from other results. Therapeutic anticoagulation compromises coagulation-based assays but careful data interpretation and use of alternative reagents can detect or exclude LA in specific circumstances, and this aspect of LA detection continues to evolve. This review focuses on the main areas of debate in LA detection.