Pathogenesis of antiphospholipid syndrome: understanding the antibodies

Atomistic characterization of β2-glycoprotein I domain V interaction with anionic membranes

BACKGROUND

Interaction of β2-glycoprotein I (β2GPI) with anionic membranes is crucial in antiphospholipid syndrome (APS), implicating the role of its membrane-binding domain, domain V (DV). The mechanism of DV binding to anionic lipids is not fully understood.

OBJECTIVES

This study aimed to elucidate the molecular details of β2GPI DV binding to anionic membranes.

METHODS

We utilized molecular dynamics simulations to investigate the structural basis of anionic lipid recognition by DV. To corroborate the membrane-binding mode identified in the highly mobile membrane mimetic simulations, we conducted additional simulations using a full membrane model.

RESULTS

The study identified critical regions in DV, namely the lysine-rich loop and the hydrophobic loop, which are essential for membrane association via electrostatic and hydrophobic interactions, respectively. A novel lysine pair contributing to membrane binding was also discovered, providing new insights into β2GPI's membrane interaction. Simulations revealed 2 distinct binding modes of DV to the membrane, with mode 1 characterized by the insertion of the hydrophobic loop into the lipid bilayer, suggesting a dominant mechanism for membrane association. This interaction is pivotal for the pathogenesis of APS, as it facilitates the recognition of β2GPI by antiphospholipid antibodies.

CONCLUSION

The study advances our understanding of the molecular interactions between β2GPI's DV and anionic membranes, which are crucial for APS pathogenesis. It highlights the importance of specific regions in DV for membrane binding and reveals a predominant binding mode. These findings have significant implications for APS diagnostics and therapeutics, offering a deeper insight into the molecular basis of the syndrome.

Impact of Antiphospholipid Syndrome on Reproductive Outcomes: Current Insights and Management Approaches

Antiphospholipid syndrome (APS) is a disease characterized by the presence of antiphospholipid (aPL) antibodies, thrombosis, and obstetric complications. While patients with APS can have successful pregnancies, many important considerations exist. APS can also cooccur with other systemic autoimmune diseases which can affect pregnancy, particularly systemic lupus erythematosus. This article reviews specific considerations for pregnancy and reproductive health in patients with APS. Similar to other autoimmune diseases, stable or quiescent disease and planning with a rheumatologist and obstetrician prior to conception are vital components of a successful pregnancy. Pregnancy management for patients with aPL antibodies or diagnosis of APS with aspirin and/or anticoagulation depending on disease profile is discussed, as well as the effects of physiologic changes during pregnancy in maternal and fetal outcomes for this population. Given the reproductive span lasts beyond conception through delivery, we include discussions on safe contraception options, the use of assistive reproductive technology, pregnancy termination, menopause, and male fertility. While APS is a relatively rare condition, the effects this disease can have on maternal and fetal outcomes even with available therapies demonstrates the need for more high-quality, evidence-based research.

Low-dose aspirin and heparin treatment improves pregnancy outcome in recurrent pregnancy loss women with anti-β2-glycoprotein I/HLA-DR autoantibodies: a prospective, multicenter, observational study

Introduction

Anti-β2-glycoprotein I (β2GPI)/human leukocyte antigen (HLA)-DR antibodies may be a risk factor for recurrent pregnancy loss (RPL). The therapeutic modality for women with RPL and anti-β2GPI/HLA-DR antibody positivity has not been evaluated. This prospective, multicenter, observational study aimed to assess whether low-dose aspirin (LDA) and/or heparin therapies improve pregnancy outcomes in women with RPL who tested positive for anti-β2GPI/HLA-DR antibodies.

Methods

Between August 2019 and December 2021, 462 women with RPL underwent anti-β2GPI/HLA-DR antibody measurements and risk assessments for RPL. Each attending physician decided the treatment modality for women with RPL who tested positive for anti-β2GPI/HLA-DR antibodies, and their pregnancy outcomes were followed up until December 2023. Finally, 47 pregnancies in 47 women with RPL and anti-β2GPI/HLA-DR antibody positivity were included in the analysis and were divided into two groups regarding whether they were treated with LDA and/or unfractionated heparin (UFH) (LDA/UFH group, n = 39) or with neither of them (non-LDA/non-UFH group, n = 8). The rates of live birth and pregnancy complications (i.e., preeclampsia and preterm delivery before 34 gestational weeks due to placental insufficiency) were compared between the two groups.

Results

The live birth rate in the LDA/UFH group was higher than that in the non-LDA/non-UFH group (87.2% vs 50.0%, p = 0.03). The pregnancy complication rate in the LDA/UFH group was significantly lower than that in the non-LDA/non-UFH group (5.9% vs 50.0%, p = 0.048). Among 21 women who tested positive for anti-β2GPI/HLA-DR antibodies and had no other risk factors for RPL, the live birth rate in the LDA/UFH group (n = 14) was much higher than that in the non-LDA/non-UFH group (n = 7) (92.9% vs 42.9%, p = 0.03).

Discussion

This study, for the first time, demonstrated that LDA and/or UFH therapies are effective in improving pregnancy outcomes in women with RPL and aβ2GPI/HLA-DR antibody positivity.

Antibodies and complement are key drivers of thrombosis

Venous thromboembolism (VTE) is a common, deadly disease with an increasing incidence despite preventive efforts. Clinical observations have associated elevated antibody concentrations or antibody-based therapies with thrombotic events. However, how antibodies contribute to thrombosis is unknown. Here, we show that reduced blood flow enabled immunoglobulin M (IgM) to bind to FcμR and the polymeric immunoglobulin receptor (pIgR), initiating endothelial activation and platelet recruitment. Subsequently, the procoagulant surface of activated platelets accommodated antigen- and FcγR-independent IgG deposition. This leads to classical complement activation, setting in motion a prothrombotic vicious circle. Key elements of this mechanism were present in humans in the setting of venous stasis as well as in the dysregulated immunothrombosis of COVID-19. This antibody-driven thrombosis can be prevented by pharmacologically targeting complement. Hence, our results uncover antibodies as previously unrecognized central regulators of thrombosis. These findings carry relevance for therapeutic application of antibodies and open innovative avenues to target thrombosis without compromising hemostasis.

The role of complement in kidney disease: conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference

Uncontrolled complement activation can cause or contribute to glomerular injury in multiple kidney diseases. Although complement activation plays a causal role in atypical hemolytic uremic syndrome and C3 glomerulopathy, over the past decade, a rapidly accumulating body of evidence has shown a role for complement activation in multiple other kidney diseases, including diabetic nephropathy and several glomerulonephritides. The number of available complement inhibitor therapies has also increased during the same period. In 2022, Kidney Diseases: Improving Global Outcomes (KDIGO) convened a Controversies Conference, "The Role of Complement in Kidney Disease," to address the expanding role of complement dysregulation in the pathophysiology, diagnosis, and management of various glomerular diseases, diabetic nephropathy, and other forms of hemolytic uremic syndrome. Conference participants reviewed the evidence for complement playing a primary causal or secondary role in progression for several disease states and considered how evidence of complement involvement might inform management. Participating patients with various complement-mediated diseases and caregivers described concerns related to life planning, implications surrounding genetic testing, and the need for inclusive implementation of effective novel therapies into clinical practice. The value of biomarkers in monitoring disease course and the role of the glomerular microenvironment in complement response were examined, and key gaps in knowledge and research priorities were identified.

Catastrophic Antiphospholipid Syndrome: A Review of Current Evidence and Future Management Practices

Antiphospholipid syndrome (APS) is an autoimmune disorder characterized by blood clots and pregnancy complications due to antiphospholipid antibodies. Catastrophic APS (CAPS), a severe variant, leads to multiorgan failure and is often fatal. Pathogenesis involves antiphospholipid antibodies, particularly anti-beta-2-glycoprotein I (aβ2GPI), which trigger endothelial cell (EC) activation, cytokine release, and a prothrombotic state. Infections, surgeries, and other triggers can precipitate CAPS, leading to widespread microthromboses and systemic inflammatory responses. CAPS predominantly affects younger patients and those with systemic lupus erythematosus (SLE), with a high mortality rate, though recent treatment advances have improved survival. Diagnosing CAPS involves identifying clinical manifestations, including rapid organ involvement and small vessel occlusions, confirmed by histopathology and high antiphospholipid antibody levels. The CAPS registry data indicate that commonly affected organs include kidneys, lungs, central nervous system, and the heart, with a high prevalence of lupus anticoagulant and anticardiolipin antibodies (aCL). Current management strategies focus on therapeutic anticoagulation, immunosuppressive therapies like corticosteroids, and adjunct treatments such as plasmapheresis and intravenous immunoglobulin (IVIG). Early use of glucocorticoids and combination therapy has significantly improved outcomes. In life-threatening cases, especially with microangiopathy, experts recommend performing plasma exchange (PE). Patients with associated autoimmune conditions or refractory cases may receive cyclophosphamide (CY) and rituximab while considering PE for treatment. Maintenance of anticoagulation with an appropriate international normalized ratio (INR) is crucial to prevent recurrence. This article reviews the pathogenesis and epidemiology of CAPS. It also examines the current management strategies, and discusses the challenges and controversies associated with these strategies. It hereafter offers recommendations for future management and outlines directions for further research.

Comparative assessment of the diagnostic performances of particle-based multianalyte technology and commercial ELISA for antiphospholipid autoantibody testing

BACKGROUND

Diagnosing Antiphospholipid Syndrome (APS) relies heavily on laboratory findings, particularly the detection of specific antibodies like lupus anticoagulant (LA), IgG and/or IgM anti-cardiolipin (aCL), and IgG and/or IgM anti-β2 glycoprotein 1 (aB2GP1). Although ELISA is widely used in the US for this purpose, standardization between different assay methodologies remains challenging, leading to significant variability across laboratories. Particle-based multi-analyte technology (PMAT) offers a streamlined one-step detection for all six antiphospholipid (aPL) autoantibodies, covering aCL and aB2GP1 of IgA, IgG, and IgM isotypes.

METHODS

In this study involving 224 subjects, including 34 clinically diagnosed with APS, alongside 160 non-APS patients and 30 healthy donors, PMAT's performance was evaluated against commercial ELISA in detecting aPL antibodies.

RESULTS

At the manufacturer's suggested cutoff, PMAT exhibited sensitivity comparable to ELISA, albeit with a low to moderate decrease in specificity for certain antibodies. With anti-CL IgM alone, PMAT displayed a 17.7% decrease in sensitivity, accompanied by a corresponding 31.1% increase in specificity compared to ELISA. However, applying a stricter cutoff (88-90% specificity), IgA and IgM antibodies yielded 5.9-17.6% higher sensitivities with PMAT, and IgG antibodies displayed similar sensitivity.

CONCLUSIONS

In this study cohort, PMAT demonstrated higher or comparable sensitivity to that of commercial ELISA for all six aPL antibodies at a specificity cutoff near 90%. Notably, PMAT demonstrated superior sensitivity and specificity overall in detecting IgA aCL and aB2GP1 antibodies. This study highlights the potential of automated PMAT for detecting aPL antibodies in APS evaluation.

Antiphospholipid Antibody Testing in a Maximum Care Hospital: Method-Dependent Differences

Background: Antiphospholipid antibody (aPL) testing is critical for the classification of antiphospholipid syndrome. The 2023 ACR/EULAR classification criteria recommend the use of enzyme-linked immunosorbent assays (ELISAs) and specific thresholds for aPL positivity. Since non-ELISA methods are increasingly used, we compared and evaluated ELISA and non-ELISA aPL assays in a real-world maximum care hospital setting. Methods: Between January 2021 and June 2024, anticardiolipin (aCL; IgG and IgM) and anti-beta2 glycoprotein I (aß2GPI; IgG and IgM) antibodies were measured using ELISA (n = 5115) and a chemiluminescence-based automated immunoassay (CLIA) (n = 3820). Results of parallel testing were compared, and associations with clinical and laboratory characteristics were evaluated. Results: A total of 946 samples were tested using ELISA and CLIA in parallel. A total of 136 (14%) specimens were positive for at least one aPL, and 55 (6%) specimens were from patients diagnosed with APS. Among the latter, 47 (85%) and 41 (75%) patients were positive when ELISA- or CLIA-based aPL assays were used, respectively. After applying the >40 units threshold of the new classification criteria, the number of aPL-positive specimens was significantly lower. In the entire cohort, the agreement between ELISA and CLIA aPL assays was acceptable only for aß2GPI IgG; the results from the two methods did not agree for aCL IgG/IgM and aß2GPI IgM. In APS patients, the agreement between ELISA and CLIA aPL assays was acceptable for aß2GPI IgG and IgM but poor for aCL IgG and IgM. Antibody levels in APS patients were significantly higher using CLIA compared to ELISA. Conclusions: The method-dependent discrepancies between ELISA- and CLIA-based aPL assays regarding the quantitative and qualitative results are substantial. Both methods are suitable for APS classification, but the choice of aPL assay may influence the classification, and therefore, aPL results should be interpreted carefully in the clinical context.

Establishment of ELISA-comparable moderate and high thresholds for anticardiolipin and anti-β2 glycoprotein I chemiluminescent immunoassays according to the 2023 ACR/EULAR APS classification criteria and evaluation of their diagnostic performance

OBJECTIVES

Recently published 2023 ACR/EULAR APS classification criteria emphasize the importance of quantifying single-, double-, and triple-antiphospholipid antibody positivity, distinguishing between IgG and IgM isotypes, and delineating moderate/high levels of anticardiolipin (aCL) and anti-β2 glycoprotein I (anti-β2GPI) antibodies. We aimed to establish clinically important moderate/high thresholds for aCL and anti-β2GPI IgG/IgM chemiluminescent immunoassays (CLIA), in particular QUANTA Flash, comparable to our in-house ELISAs used for over two decades, and to evaluate their diagnostic performance.

METHODS

QUANTA Flash CLIA and in-house ELISAs were used to measure aCL and anti-β2GPI IgG/IgM. Moderate thresholds for QUANTA Flash CLIA were determined using a non-parametric approach, calculating a 99th percentile on serum samples from 139 blood donors, and by mirroring the diagnostic performance of in-house ELISA on 159 patient samples.

RESULTS

Thresholds for QUANTA Flash CLIA achieving diagnostic performance equivalent to in-house ELISAs were 40 CU for moderate and 80 CU for high levels for aCL and anti-β2GPI IgG and IgM. The assays showed good qualitative agreement, ranging from 76.10 to 91.19 %. When considering in-house ELISA results, 14 out of 80 (17.5 %) patients did not fulfill the new ACR/EULAR laboratory classification criteria, while 27 out of 80 (33.8 %) did not when considering QUANTA Flash CLIA results.

CONCLUSIONS

We determined moderate and high thresholds for aCL and anti-β2GPI IgG and IgM detected with QUANTA Flash CLIA, aligning with long-established in-house ELISA thresholds. These thresholds are crucial for seamlessly integrating of the new 2023 ACR/EULAR classification criteria into future observational clinical studies and trials.

Effect of smoking on thrombotic antiphospholipid syndrome: a 10-year prospective cohort study

OBJECTIVES

Cigarette smoking is an established risk factor for autoimmune diseases. However, whether smoking plays a clear role in thrombotic APS (TAPS) has not been determined. We aimed to investigate the effects of smoking on the clinical characteristics and prognosis of TAPS.

METHODS

This was a prospective cohort study from 2013 to 2022. During the study period, 297 patients were diagnosed with TAPS, including 82 smokers and 215 non-smokers. After propensity score matching, 57 smokers and 57 non-smokers matched by age and sex were analysed.

RESULTS

Overall, smokers with TAPS had more cardiovascular risk factors than non-smokers, including hypertension (36.59% vs 14.42%, P < 0.001), obesity (15.85% vs 7.44%, P = 0.029), dyslipidaemia (64.63% vs 48.37%, P = 0.012) and hyperhomocysteinaemia (62.20% vs 36.28%, P < 0.001). Arterial thrombotic events were more common in smokers at diagnosis (62.20% vs 46.05%, P = 0.013), especially myocardial infarction, visceral thrombosis and peripheral vascular thrombosis. After matching, smokers showed balanced cardiovascular risk factors with non-smokers at baseline, but retained a higher prevalence of arterial thrombosis (59.65% vs 33.33%, P = 0.005), mainly distributed in cerebral vascular, cardiovascula and retinal vascular territories. During follow-up, smokers presented a tendency for more recurrent arterial thrombosis and less recurrent venous thrombosis. Smokers had significantly poorer outcomes for organ damage with higher Damage Index for APS score (median 2.00 vs 1.00, P = 0.008), especially in the cardiovascular (26.32% vs 3.51%, P = 0.001), gastrointestinal (15.79% vs 1.75%, P = 0.016) and ophthalmologic (10.53% vs 00.00%, P = 0.027) systems.

CONCLUSION

Smoking is related to increased arterial events and poor prognosis in TAPS patients. Patients with TAPS should be fully encouraged to avoid smoking.

Biological markers of high risk of thrombotic recurrence in patients with antiphospholipid syndrome: A literature review

OBJECTIVES

This review aims to identify biological markers associated with the risk of recurrence of thrombotic and/or obstetric events in patients with antiphospholipid syndrome (APS).

METHODS

A comprehensive review of literature was conducted to evaluate established and potential novel biological markers associated with thrombosis in APS. To this end, a PubMed literature search was conducted for the last twenty years using the following keywords or their combinations: thrombotic risk, recurrence of thrombosis, risk stratification, severity, predictive value.

RESULTS

Previous studies showed that multiple aPL positivity correlates with an increased risk of thrombosis in APS. Moreover, the analysis of N-glycosylation of antiphospholipid antibodies (aPL) revealed that low levels of IgG sialylation, fucosylation or galactosylation increases the pro-inflammatory activity of aPL, predisposing to thrombosis. In addition, quantification of neutrophil extracellular traps (NETs) and antibodies directed against NETs (anti-NETs) in serum demonstrates promising prognostic utility in assessing APS severity. Oxidative stress plays a role in the pathogenicity of APS and paraoxonase 1 (PON1) activity emerges as a promising biomarker of thrombotic risk in APS. Furthermore, identification of novel antigenic targets involved in the pathophysiology of APS, such as lysobisphosphatidic acid (LBPA), had led to the discovery of unconventional aPL, antibodies directed against the LBPA (aLBPA), whose clinical value could make it possible to identify APS patients at high risk of thrombotic recurrence.

CONCLUSION

The immunological profile of aPL, N-glycosylation of aPL, quantification of NETs and anti-NETs, analysis of biomarkers of oxidative stress and the discovery of aLBPA offer potential prognostic tools for risk stratification in APS patients.

Clinical and Laboratory Diagnosis of Antiphospholipid Syndrome: A Review

The antiphospholipid syndrome (APS) manifests through venous or arterial thrombosis, with or without pregnancy complication alongside the continuous presence of antiphospholipid antibodies (aPL). APS classification relies on three aPL subtypes: anticardiolipin (aCL), anti-β2-glycoprotein I antibodies (anti-β2GPI), and lupus anticoagulants (LA) antibodies. Given that thrombosis and pregnancy issues are not unique to APS, the precise and reliable identification of aPL forms the basis for diagnosis. Semi-quantitative solid-phase assays identify two antibodies, aCL and anti-β2GPI, while LA detection occurs through various phospholipid-dependent coagulation assays that are based on antibody behaviour. LA, specifically, is conclusively associated with thrombosis, prompting discussions around the serological criteria for APS. Despite advancements in LA detection, the standardisation of all aPL detection assays remains imperative. The combined presence of aCL and anti-β2GPI with thrombosis inconsistently triggers concern. Initial presentations by APS patients commonly exhibit a heightened risk of stroke, miscarriages in the later stages of pregnancy, positive results of LA tests, and widespread thrombosis across multiple organs, often leading to adverse outcomes. Correctly diagnosing this condition is pivotal to avoid unnecessary long-term secondary thromboprophylaxis.

[Obstetric Antiphospholipid Syndrome: Insights on the Diagnosis, Treatment, and Hot Issues]

Obstetric antiphospholipid syndrome (OAPS) is an autoimmune disorder associated with various pathological pregnancies, such as recurrent miscarriage, stillbirth, severe pre-eclampsia and severe placental insufficiency. The persistent presence of antiphospholipid antibodies (aPLs) is the most important laboratory characteristic of OAPS. OAPS severely affects the reproductive health of women of childbearing age in China. Reports indicate that approximately 9.6% stillbirths, 11.5% severe pre-eclampsia, and 54% recurrent miscarriages are associated with OAPS or aPLs. However, the pathogenesis of OAPS remains unclear. Previously, thrombosis at the maternal-fetal interface (MFI) was considered the main mechanism of OAPS-related pathological pregnancies. Consequently, the use of low molecular weight heparin and aspirin throughout pregnancy was recommended to improve outcomes in OAPS patient. In recent years, many studies have found that thrombosis in MFI is uncommon, but various inflammatory factors are significantly increased in the MFI of OAPS patients. Based on these findings, some clinicians have started using anti-inflammatory treatments for OAPS, which have preliminarily improved the pregnancy outcomes. Nevertheless, there is no consensus on these second-line treatments of OAPS. Another troubling issue is the clinical diagnosis of OAPS. Similar to other autoimmune diseases, there are only classification criteria for OAPS, and clinical diagnosis of OAPS depends on the clinicians' experience. The present classification criteria of OAPS were established for clinical and basic research purposes, not for patient clinical management. In clinical practice, many patients with both positive aPLs and pathological pregnancy histories do not meet the strict OAPS criteria. This has led to widespread issues of incorrect diagnosis and treatment. Timely and accurate diagnosis of OAPS is crucial for effective treatment. In this article, we reviewed the epidemiological research progress on OAPS and summarized its classification principles, including: 1) the persistent presence of aPLs in circulation; 2) manifestations of OAPS, excluding other possible causes. For the first point, accurate assessment of aPLs is crucial; for the latter, previous studies regarded only placenta-related pregnancy complications as characteristic manifestations of OAPS. However, recent studies have indicated that adverse pregnancy outcomes related to trophoblast damage, such as recurrent miscarriage and stillbirth, also need to be considered in OAPS. We also discussed several key issues in the diagnosis and treatment of OAPS. First, we addressed the definition of non-standard OAPS and offered our opinion on defining non-standard OAPS within the framework of the 2023 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) APS criteria. Then, we discussed the advantages and disadvantages of different aPL testing methods, emphasizing that harmonizing results across platforms and establishing specific reference values are keys to resolving controversies in aPL testing results. We also introduced the application of non-criteria aPLs, especially anti-phosphatidylserine/prothrombin antibody (aPS/PT) and anti-β2 glycoprotein Ⅰ domain Ⅰ antibody (aβ2GPⅠDⅠ). Additionally, we discussed aPL-based OAPS risk classification strategies. Finally, we proposed potential treatment methods for refractory OAPS. The goal is to provide a reference for the clinical management of OAPS.

Noncriteria antiphospholipid antibodies in antiphospholipid syndrome

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by thrombotic manifestations and/or obstetric complications in patients with persistently positive antiphospholipid antibodies (aPL). aPL are a heterogeneous group of autoantibodies, but only lupus anticoagulant, anticardiolipin (aCL), and antibeta2-glycoprotein I antibodies (aβ2GPI) IgG or IgM are included as laboratory classification criteria. Seronegative APS patients are usually defined as patients with the clinical symptoms of APS but who test negative for aPL. The negativity to classic aPL criteria does not exclude the presence of other aPL. Several noncriteria aPL have been identified. Some noncriteria aPL are well studied, such as IgA aCL and aβ2GPI, the antiphosphatidylserine-prothrombin (aPS/PT) antibodies, and the antibodies against the domain I of beta2-glycoprotein I (aDI), both latter groups receiving more attention for their role in thrombotic events and pregnancy complications. Other noncriteria aPL that have been studied are antibodies against annexin V, prothrombin, phosphatidylethanolamine, phosphatidic acid, phosphatidylserine, phosphatidylinositol, vimentin-cardiolipin complex, anti-protein S/protein C. Measurement of some of these noncriteria aPL (aPS/PT, aDI) is useful in the laboratory work-out of APS in specific situations. We have to differentiate between patients who are positive for noncriteria aPL only, and patients who have both criteria and noncriteria aPL to enable us to study their role in the diagnosis or risk stratification of APS. The research on noncriteria aPL is continually developing as the clinical relevance of these antibodies is not yet fully clarified.

Antiphospholipid syndrome, thrombosis, and vaccination in the COVID-19 pandemic

Thrombosis is one of the many signs of antiphospholipid syndrome (APS) and COVID-19 infection. Although the mechanisms contributing to thrombosis in APS and COVID-19 are relatively similar, this remains an open subject. Even now (when the COVID-19 pandemic has subsided), there is no conclusive solution to APS and COVID-19 co-occurrence. The presence of newly generated antiphospholipid antibodies (aPLs) in COVID-19 infection may or may not be connected to the diagnosis of APS. The prevalence of aPLs is substantial in severe COVID-19 but not related to thrombosis or a worse outcome. Adequate monitoring of antibody positivity over time is recommended for APL diagnosis. On the other hand, thrombosis and thrombocytopenia can rarely occur with vaccination with mRNA vaccines. Some studies have shown that COVID-19 immunization is well tolerated among APS patients who are triple-positive for aPL, which may comfort patients and referring physicians and lessen hesitation in unvaccinated APS/aPL-positive patients. In this narrative review, we will give an overview of the interaction between aPL-APS-COVID-19-thrombosis and related diagnostic insights learned during the pandemic.

New method to differentiate between lupus anticoagulants, progressive coagulation inhibitors and coagulation factor deficiencies in the mixing tests

INTRODUCTION

Mixing tests in activated partial thromboplastin time (APTT) are used for the differentiation between lupus anticoagulants (LA), coagulation inhibitors, and factor deficient samples with APTT prolongation. However, the indexes for the differentiation have not been established. The present study aimed to develop new mixing test indexes for the differentiation.

METHODS

Twenty-six LA-positive, 8 progressive coagulation factor VIII inhibitor, and 35 coagulation deficient samples were employed. APTT were measured for normal plasma, patient plasma, and mixing plasma prepared at a ratio of 1:1 proportion in both without incubation and 2 h-incubation. New two parameters named as ALD50 and mixture plasma-patient plasma after Warming change rate Subtraction (WaS) calculated from the clotting times of normal, 1:1 mixing and patient samples with/without 2 h-incubation were established. In the samples with WaS result of <10.2%, ALD50 of ≥87.8%, and < 87.8% were defined as LA and coagulation factor deficiency, respectively, and WaS of ≥10.2% defined progressive coagulation factor inhibitors.

RESULTS

Sensitivity and specificity to LA were 80.8% and 93.0% for ALD50, and sensitivity and specificity to progressive coagulation factor inhibitor were 100.0% and 100.0% for WaS, respectively. The agreement between sample classification and WaS-ALD50 was 88.4% (61/69).

CONCLUSIONS

ALD50 and WaS showed acceptable sensitivity and specificity to LA and progressive coagulation factor inhibitor, respectively. These indexes would be useful for the differentiation between LA, factor deficiency, and progressive coagulation factor inhibitor in the mixing tests.

Antiphospholipid antibody-related hepatic vasculitis in a juvenile after non-severe COVID-19: a case report and literature review

Antiphospholipid antibodies (aPL) are both laboratory evidence and causative factors for a broad spectrum of clinical manifestations of antiphospholipid syndrome (APS), with thrombotic and obstetric events being the most prevalent. Despite the aPL-triggered vasculopathy nature of APS, vasculitic-like manifestations rarely exist in APS and mainly appear associated with other concurrent connective tissue diseases like systemic lupus erythematous. Several studies have characterized pulmonary capillaritis related to pathogenic aPL, suggesting vasculitis as a potential associated non-thrombotic manifestation. Here, we describe a 15-year-old girl who develops hepatic infarction in the presence of highly positive aPL, temporally related to prior non-severe COVID-19 infection. aPL-related hepatic vasculitis, which has not been reported before, contributes to liver ischemic necrosis. Immunosuppression therapy brings about favorable outcomes. Our case together with retrieved literature provides supportive evidence for aPL-related vasculitis, extending the spectrum of vascular changes raised by pathogenic aPL. Differentiation between thrombotic and vasculitic forms of vascular lesions is essential for appropriate therapeutic decision to include additional immunosuppression therapy. We also perform a systematic review to characterize the prevalence and clinical features of new-onset APS and APS relapses after COVID-19 for the first time, indicating the pathogenicity of aPL in a subset of COVID-19 patients.

An immunogenomic exome landscape of triple positive primary antiphospholipid patients

Primary antiphospholipid syndrome is characterized by thrombosis and autoantibodies directed against phospholipids or associated proteins. The genetic etiology of PAPS remains unknown. We enrolled 21 patients with thromboembolic events associated to lupus anticoagulant, anticardiolipin and anti β2 glycoprotein1 autoantibodies. We performed whole exome sequencing and a systematic variant-based analysis in genes associated with thrombosis, in candidate genes previously associated with APS or inborn errors of immunity. Data were compared to public databases and to a control cohort of 873 non-autoimmune patients. Variants were identified following a state-of-the-art pipeline. Enrichment analysis was performed by comparing with the control cohort. We found an absence of significant HLA bias and genetic heterogeneity in these patients, including when testing combinations of rare variants in genes encoding for proteins involved in thrombosis and of variants in genes linked with inborn errors of immunity. These results provide evidence of genetic heterogeneity in PAPS, even in a homogenous series of triple positive patients. At the individual scale, a combination of variants may participate to the breakdown of B cell tolerance and to the vessel damage.

Atomistic Characterization of Beta-2-Glycoprotein I Domain V Interaction with Anionic Membranes

Background

Interaction of beta-2-glycoprotein I ( β 2 GPI) with anionic membranes is crucial in antiphospholipid syndrome (APS), implicating the role of it's membrane bind-ing domain, Domain V (DV). The mechanism of DV binding to anionic lipids is not fully understood.

Objectives

This study aims to elucidate the mechanism by which DV of β 2 GPI binds to anionic membranes.

Methods

We utilized molecular dynamics (MD) simulations to investigate the struc-tural basis of anionic lipid recognition by DV. To corroborate the membrane-binding mode identified in the HMMM simulations, we conducted additional simulations using a full mem-brane model.

Results

The study identified critical regions in DV, namely the lysine-rich loop and the hydrophobic loop, essential for membrane association via electrostatic and hydrophobic interactions, respectively. A novel lysine pair contributing to membrane binding was also discovered, providing new insights into β 2 GPI's membrane interaction. Simulations revealed two distinct binding modes of DV to the membrane, with mode 1 characterized by the insertion of the hydrophobic loop into the lipid bilayer, suggesting a dominant mechanism for membrane association. This interaction is pivotal for the pathogenesis of APS, as it facilitates the recognition of β 2 GPI by antiphospholipid antibodies.

Conclusion

The study advances our understanding of the molecular interactions be-tween β 2 GPI's DV and anionic membranes, crucial for APS pathogenesis. It highlights the importance of specific regions in DV for membrane binding and reveals a predominant bind-ing mode. These findings have significant implications for APS diagnostics and therapeutics, offering a deeper insight into the molecular basis of the syndrome.

Profile and clinical relevance of non-criteria antiphospholipid antibodies in patients diagnosed with or highly suspected of APS

OBJECTIVE

This study investigates the positivity and relevance of non-criteria aPLs with clinical phenotypes in patients highly suspected of or diagnosed with APS.

METHODS

Outpatient cases were included from a prospectively maintained database, and patients were grouped into APS (n = 168), seronegative APS (SNAPS, n = 9), those meeting the diagnostic criteria for clinical events without laboratory results (only-event, n = 15), those that had aPL positivity without clinical manifestations (asymptomatic APA, n = 39), and healthy controls (n = 88). Criteria aPL results and APS-related clinical features were extracted. Sixteen non-criteria aPLs were tested and analysed.

RESULTS

LA, aCL and anti-β2 glycoprotein-I were positive in 84.5%, 61.3% and 74.4% of APS patients, and 61.5%, 59.0% and 74.4% of asymptomatic APA patients, respectively. In patients negative for criteria serological tests, 23 out of 24 were positive for at least one non-criteria aPL. Triple-positive patients also had significantly higher tests of some aPLs in comparison with other groups. Stroke was associated with anti-phosphatidyl-inositol (aPI) IgG and anti-phosphatidyl-glycerol (aPG) IgG. Late embryonic loss correlated with aPI IgM, and premature birth/eclampsia was associated with aPI IgG and aPG IgG. There were also positive associations between heart valve lesions and anti-phosphatidylserine-prothrombin (aPS/PT) IgM, APS nephropathy and anti-phosphatidyl-choline IgG or aPS/PT IgG, and livedo reticularis and anti-phosphatidyl-ethanolamine IgM.

CONCLUSION

The prevalence of non-criteria aPLs differed from diagnostic biomarkers in patients diagnosed with or suspected of APS. Detection of aPLs provided additive value in the evaluation of APS-related clinical manifestations.

Are Antiphospholipid Antibodies a Surrogate Risk Factor for Thrombosis in Sepsis?

Antiphospholipid syndrome (APS) is a hypercoagulable state caused by antiphospholipid antibodies (aPL). APS clinically manifests with arterial or venous or microvascular thrombi and/or pregnancy complications. It is well-known that the development of aPL can be a transient phenomenon and thus the current diagnostic criterion for APS requires repeat laboratory testing several weeks apart before a definitive diagnosis is made. However, transient presence of aPL may also be pathogenic. In this article, we attempt to give historical and clinical evidence for the importance of these antibodies, even when transient, and call for further research into mechanisms by which these antibodies may promote thrombosis and pregnancy morbidities.

Damage measured by Damage Index for Antiphospholipid Syndrome (DIAPS) in antiphospholipid antibody-positive patients included in the APS ACTION registry

OBJECTIVES

Our primary objective was to quantify damage burden measured by Damage Index for Antiphospholipid Syndrome (DIAPS) in aPL-positive patients with or without a history of thrombosis in an international cohort (the APS ACTION cohort). Secondly, we aimed to identify clinical and laboratory characteristics associated with damage in aPL-positive patients.

METHODS

In this cross-sectional study, we analysed the baseline damage in aPL-positive patients with or without APS classification. We excluded patients with other autoimmune diseases. We analysed the demographic, clinical and laboratory characteristics based on two subgroups: (i) thrombotic APS patients with high vs low damage; and (ii) non-thrombotic aPL-positive patients with vs without damage.

RESULTS

Of the 826 aPL-positive patients included in the registry as of April 2020, 586 with no other systemic autoimmune diseases were included in the analysis (412 thrombotic and 174 non-thrombotic). In the thrombotic group, hyperlipidaemia (odds ratio [OR] 1.82; 95% CI 1.05, 3.15; adjusted P = 0.032), obesity (OR 2.14; 95% CI 1.23, 3.71; adjusted P = 0.007), aβ2GPI high titres (OR 2.33; 95% CI 1.36, 4.02; adjusted P = 0.002) and corticosteroid use (ever) (OR 3.73; 95% CI 1.80, 7.75; adjusted P < 0.001) were independently associated with high damage at baseline. In the non-thrombotic group, hypertension (OR 4.55; 95% CI 1.82, 11.35; adjusted P = 0.001) and hyperlipidaemia (OR 4.32; 95% CI 1.37, 13.65; adjusted P = 0.013) were independent predictors of damage at baseline; conversely, single aPL positivity was inversely correlated with damage (OR 0.24; 95% CI 0.075, 0.77; adjusted P = 0.016).

CONCLUSIONS

DIAPS indicates substantial damage in aPL-positive patients in the APS ACTION cohort. Selected traditional cardiovascular risk factors, steroids use and specific aPL profiles may help to identify patients more prone to present with a higher damage burden.

Antiphospholipid syndrome pathogenesis in 2023: an update of new mechanisms or just a reconsideration of the old ones?

Antibodies against phospholipid (aPL)-binding proteins, in particular, beta 2 glycoprotein I (β2GPI), are diagnostic/classification and pathogenic antibodies in antiphospholipid syndrome (APS). β2GPI-aPL recognize their target on endothelium and trigger a pro-thrombotic phenotype which is amplified by circulating monocytes, platelets and neutrophils. Complement activation is required as supported by the lack of aPL-mediated effects in animal models when the complement cascade is blocked. The final result is a localized clot. A strong generalized inflammatory response is associated with catastrophic APS, the clinical variant characterized by systemic thrombotic microangiopathy. A two-hit hypothesis was suggested to explain why persistent aPL are associated with acute events only when a second hit allows antibody/complement binding by modulating β2GPI tissue presentation. β2GPI/β2GPI-aPL are also responsible for obstetric APS, being the molecule physiologically present in placental/decidual tissues. Additional mechanisms mediated by aPL with different characteristics have been reported, but their diagnostic/prognostic value is still a matter of research.

Pregnancy in antiphospholipid syndrome: what should a rheumatologist know?

This review focuses on the management of reproductive issues in women who have antiphospholipid syndrome (APS) or are carriers of antiphospholipid antibodies (aPL). The importance of aPL detection during preconception counselling relies on their pathogenic potential for placental insufficiency and related obstetric complications. The risk of adverse pregnancy outcomes can be minimized by individualized risk stratification and tailored treatment aimed at preventing placental insufficiency. Combination therapy of low-dose acetylsalicylic acid and heparin is the mainstay of prophylaxis during pregnancy; immunomodulation, especially with hydroxychloroquine, should be considered in refractory cases. Supplementary ultrasound surveillance is useful to detect fetal growth restriction and correctly tailor the time of delivery. The individual aPL profile must be considered in the stratification of thrombotic risk, such as during assisted reproduction techniques requiring hormonal ovarian stimulation or during the follow-up after pregnancy in order to prevent the first vascular event.

Clinical Evaluation and Management of Thrombotic Microangiopathy

Thrombotic microangiopathy (TMA) refers to a diverse group of diseases that share clinical and histopathologic features. TMA is clinically characterized by microangiopathic hemolytic anemia, consumptive thrombocytopenia, and organ injury that stems from endothelial damage and vascular occlusion. There are several disease states with distinct pathophysiological mechanisms that manifest as TMA. These conditions are associated with significant morbidity and mortality and require urgent recognition and treatment. Thrombotic thrombocytopenic purpura and hemolytic uremic syndrome are traditionally considered to be primary forms of TMA, but TMA more commonly occurs in association with a coexisting condition such as infection, pregnancy, autoimmune disease, or malignant hypertension, among others. Determining the cause of TMA is a diagnostic challenge because of limited availability of disease-specific testing. However, identifying the underlying etiology is imperative as treatment strategies differ. Our understanding of the conditions that cause TMA is evolving. Recent advances have led to improved comprehension of the varying pathogenic mechanisms that drive TMA. Development of targeted therapeutics has resulted in significant improvements in patient outcomes. In this article, we review the pathogenesis and clinical features of the different TMA-causing conditions. We outline a practical approach to diagnosis and management and discuss empiric and disease-specific treatment strategies.

A young woman with acute coronary syndrome and antiphospholipid syndrome. Is it the antiphospholipid syndrome or COVID-19 vaccination or classical risk as the risk factor? a case report

BACKGROUND

Acute coronary syndrome (ACS) in young women is poorly understood due to underdiagnosis and undertreatment. One of the possible risk factors for ACS in young women is antiphospholipid syndrome (APS). Coronavirus disease 2019 (COVID-19) vaccination also emerged as one of the possible risk factors for ACS during the COVID-19 pandemic.

CASE PRESENTATION

Our patient, a 39-year-old Batak woman with dyslipidemia and family history of cardiovascular disease, experienced chest pain slightly improved at rest accompanied by autonomic symptoms. She was diagnosed with non-ST-elevation myocardial infarction (NSTEMI) based on her clinical features, dynamic electrocardiogram changes, troponin elevation, and multislice computed tomography angiography confirmed with diagnostic catheterization. The patient was managed by percutaneous coronary intervention with implantation of drug-eluting stents. On follow-up, the patient was diagnosed with APS based on history of preeclampsia with severe features in the first and third pregnancy, spontaneous abortion in the second pregnancy, history of transient ischemic attack, moderately positive lupus anticoagulant on two occasions with an interval of 12 weeks, and ACS. Further investigation revealed a history of COVID-19 vaccination with Sinovac four and six weeks before presentation. The patient was recommended for lifelong warfarin and short-term dual antiplatelet (aspirin and ticagrelor).

CONCLUSIONS

Young women are not completely immune to ACS as evident in this case of ACS in a young woman with classical risk factors (dyslipidemia and family history of cardiovascular disease) and APS. Further studies are required to fill the knowledge gap on whether COVID-19 vaccination had any contribution to the ACS in the young woman.

Catastrophic Antiphospholipid Syndrome

Unlike classic APS, CAPS causes multiple microthrombosis due to an increased inflammatory response, known as a "thrombotic storm". CAPS typically develops after infection, trauma, or surgery and begins with the following symptoms: fever, thrombocytopenia, muscle weakness, visual and cognitive disturbances, abdominal pain, renal failure, and disseminated intravascular coagulation. Although the presence of antiphospholipid antibodies in the blood is one of the diagnostic criteria, the level of these antibodies can fluctuate significantly, which complicates the diagnostic process and can lead to erroneous interpretation of rapidly developing symptoms. Triple therapy is often used to treat CAPS, which includes the use of anticoagulants, plasmapheresis, and high doses of glucocorticosteroids and, in some cases, additional intravenous immunoglobulins. The use of LMWH is recommended as the drug of choice due to its anti-inflammatory and anticoagulant properties. CAPS is a multifactorial disease that requires not only an interdisciplinary approach but also highly qualified medical care, adequate and timely diagnosis, and appropriate prevention in the context of relapse or occurrence of the disease. Improved new clinical protocols and education of medical personnel regarding CAPS can significantly improve the therapeutic approach and reduce mortality rates.

Structural analyses of β2-glycoprotein I: is there a circular conformation?

BACKGROUND

Antiphospholipid antibodies targeting β2-glycoprotein I (β2GPI) cause thrombosis and pregnancy morbidity in antiphospholipid syndrome (APS) patients. How these antibodies recognize β2GPI remains controversial.

OBJECTIVES

This study aimed to elucidate the structure of β2GPI and evaluate how pathogenic anti-domain I (DI) antibodies recognize it in human plasma.

METHODS

β2GPI was made recombinant and purified from human plasma using different protocols. Structural and functional analyses were conducted using orthogonal techniques, namely, electron microscopy, size-exclusion chromatography, single-molecule Förster resonance energy transfer, and microfluidic diffusional sizing.

RESULTS

Electron microscopy and size-exclusion chromatography showed that the structure of β2GPI produced recombinantly and purified from plasma is elongated, even when subjected to conditions previously reported to favor circularization. Single-molecule Förster resonance energy transfer analyses of β2GPI labeled at positions 88 in DII and 278 in DV showed that these residues are located >90 Å apart, consistent with an elongated form. They also documented that the distance between these 2 residues did not change when the protein was reconstituted in human plasma. Microfluidic diffusional sizing documented that β2GPI binds with moderate affinity to a prototypical anti-DI antibody targeting the epitope G40-R43 despite being elongated.

CONCLUSION

Circulating β2GPI is elongated and, therefore, fully capable of binding to anti-DI antibodies. Binding of β2GPI to negatively charged phospholipids drives autoantibody recognition by increasing the local concentration of the antigen and not by dramatically changing its conformation. These findings clarify the structural properties of β2GPI, which have important implications for understanding APS pathogenesis and the development of APS diagnostics and therapeutics.

Comorbid association of obstructive sleep apnea (OSA) and thrombotic primary antiphospholipid syndrome (tPAPS): A more severe phenotype?

OBJECTIVE

We aimed to evaluate the frequency of obstructive sleep apnea (OSA) in patients with thrombotic primary antiphospholipid syndrome (tPAPS), to investigate the performance of screening tools for OSA in this scenario and to compare clinical/laboratorial differences in tPAPS patients with and without OSA.

METHODS

We consecutively enrolled patients with tPAPS to undergo sleep studies using a portable monitor. OSA was defined as apnea-hypopnea index ≥15 events/h. Frequency of OSA in tPAPS was evaluated and compared with age-, gender-, and BMI-matched controls (1:3 ratio) from the Estudo Longitudinal de Saúde do Adulto (ELSA-Brasil). Next, we tested the performance of three different screening tools for assessing OSA in patients with tPAPS. Finally, patients with tPAPS were stratified according to OSA status comparing their clinical and laboratory characteristics (including damage burden measured by Damage Index for Antiphospholipid Syndrome [DIAPS] and biomarkers associated with thrombosis) using standard statistical procedures.

RESULTS

Fifty-two patients were included for analysis (females: 82.7%; mean age: 48 ± 14 years; body-mass index: 31.1 ± 6.5 Kg/m2; 25% with moderate-severe OSA). When compared to matched controls from ELSA-Brasil (n = 115), there was no significant differences in the frequencies of OSA (tPAPS: 12/42 [28.6%] vs. controls: 35/115 [30.4%], p = 0.821). Among screening tools, NoSAS had the highest area under ROC curve (AUC 0.806, CI 95% 0.672-0.939, p = 0.001), followed by STOP-Bang (AUC 0.772, CI 95% 0.607-0.938, p = 0.004). Patients with comorbid tPAPS and OSA presented higher levels of von Willebrand factor (vWF) (median 38.9 vs. 32.6, p = 0.038) and DIAPS (median 5 vs. 2, p = 0.020), when compared to those without OSA. OSA remained statistically associated with higher DIAPS, even after controlling for age, disease duration and BMI.

CONCLUSION

OSA is common in patients with tPAPS, with rates comparable to a non-referred population. Both NoSAS and STOP-Bang scores seems to be useful for screening OSA in these patients. Patients with tPAPS+OSA had higher damage burden and higher levels of vWF, which might suggest a more severe phenotype of tPAPS in this scenario.

Risk factors in antiphospholipid antibody-associated valvular heart disease: A 383-patient cohort study

Valvular heart disease (VHD) is a prevalent cardiac manifestation in antiphospholipid syndrome (APS) patients. However, risk factors and predictors for antiphospholipid antibody-associated VHD (aPL-VHD) remain vague. We aimed to assess the risk of developing aPL-VHD in aPL-positive patients, by establishing a clinical prediction model upon a cross-sectional cohort from APS-Shanghai database, including 383 APS patients and durable aPL carriers with transthoracic echocardiography investigation. The prevalence of aPL-VHD was 11.5%. Multivariate logistic regression analysis identified three independent risk factors for aPL-VHD: anti-β2GPI IgG (OR 5.970, P < 0.001), arterial thrombosis (OR 2.758, P = 0.007), and stratified estimated glomerular filtration rate levels (OR 0.534, P = 0.001). A prediction model for aPL-VHD, incorporating the three factors, was further developed, which demonstrated good discrimination with a C-index of 0.855 and 0.841 (after bootstrapping), and excellent calibration (P = 0.790). We provide a practical tool for assessing the risk of developing VHD among aPL-positive patients.

Beyond the classics: The emerging value of anti-phosphatidylserine/prothrombin antibodies in antiphospholipid syndrome

Antiphospholipid syndrome (APS) is an autoimmune disorder characterized by the presence of antiphospholipid antibodies (aPLs), which can lead to thrombosis and pregnancy complications. Within the diverse range of aPLs, anti-phosphatidylserine/prothrombin antibodies (aPS/PT) have gained significance in clinical practice. The detection of aPS/PT has proven valuable in identifying APS patients and stratifying their risk, especially when combined with other aPL tests like lupus anticoagulant (LA) and anti-β2-glycoprotein I (aβ2GPI). Multivariate analyses have confirmed aPS/PT as an independent risk factor for vascular thrombosis and obstetric complications, with its inclusion in the aPL score and the Global Anti-Phospholipid Syndrome Score (GAPSS) aiding in risk evaluation. However, challenges remain in the laboratory testing of aPS/PT, including the need for assay standardization and its lower sensitivity in certain patient populations. Further research is necessary to validate the clinical utility of aPS/PT antibodies in APS diagnosis, risk stratification, and management.

Prevalence, clinical significance, and persistence of autoantibodies in COVID-19

BACKGROUND

Interest in complications and sequelae following Coronavirus disease 2019 (COVID-19) is increasing. Several articles have reported COVID-19-associated autoimmune diseases and the association between autoantibodies and the severity of COVID-19. Thromboembolic complications are frequent in patients with COVID-19, and the anti-phospholipid antibodies (aPL) is frequently detected. We conducted this study to investigate the prevalence, clinical significance, and persistence of anti-nuclear antibodies (ANA) and aPLs in COVID-19.

METHODS

We enrolled patients diagnosed with COVID-19 with oxygen demand and admitted to a tertiary hospital in South Korea between July 2020 and March 2022. ANA and aPLs levels were assessed using an immunoassay kit.

RESULTS

A total of 248 patients were enrolled in the study. Among them, five patients were ANA-positive, and 41 were aPL-positive (IgM anti-cardiolipin (aCL) antibody in seven patients, IgG aCL in seven patients, IgM anti-β2Glycoprotein1 antibody (aβ2-GPI) in 32 patients, and IgG aβ2-GPI in one patient). Two of five ANA-positive patients, 13 of 32 IgM aβ2-GPI-positive patients, 5 of 7 IgM aCL-positive patients, and 2 of 7 IgG aCL-positive patients were eligible for follow-up analysis, and 100%, 69.2%, 40%, and 50% of the patients remained autoantibody-positive, respectively. There were no differences in clinical outcomes between the autoantibody-positive and autoantibody-negative groups, except for the IgG aCL group showing a tendency for worse outcomes.

CONCLUSION

A significant proportion of COVID-19 patients with oxygen demand were autoantibody-positive, and autoantibodies persisted for several months after symptom onset. Whether these autoantibodies are related to long-term sequelae in COVID-19 patients requires further investigation.

The pathogenesis of obstetric APS: a 2023 update

The antiphospholipid syndrome (APS) is an autoimmune disease characterized by the persistent presence of antibodies directed against phospholipids and phospholipid-binding proteins that are associated with thrombosis and pregnancy-related morbidity. The latter includes fetal deaths, premature birth and maternal complications. In the early 1990s, a distinct set of autoantibodies, termed collectively antiphospholipid antibodies (aPL), were identified as the causative agents of this disorder. Subsequently histological analyses of the placenta from APS pregnancies revealed various abnormalities, including inflammation at maternal-fetal interface and poor placentation manifested by reduced trophoblast invasion and limited uterine spiral artery remodeling. Further preclinical investigations identified the molecular targets of aPL and the downstream intracellular pathways of key placental cell types. While these discoveries suggest potential therapeutics for this disorder, definitive clinical trials have not been completed. This concise review focuses on the recent developments in the field of basic and translational research pursuing novel mechanisms underlying obstetric APS.

Thrombosis and Hyperinflammation in COVID-19 Acute Phase Are Related to Anti-Phosphatidylserine and Anti-Phosphatidylinositol Antibody Positivity

Antiphospholipid antibodies (APLA) are strongly associated with thrombosis seen in patients with antiphospholipid syndrome. In COVID-19, thrombosis has been observed as one of the main comorbidities. In patients hospitalised for COVID-19, we want to check whether APLA positivity is associated with COVID-19-related thrombosis, inflammation, severity of disease, or long COVID-19. We enrolled 92 hospitalised patients with COVID-19 between March and April 2020 who were tested for 18 different APLAs (IgG and IgM) with a single line-immunoassay test. A total of 30 healthy blood donors were used to set the cut-off for each APLA positivity. Of the 92 COVID-19 inpatients, 30 (32.61%; 95% CI [23.41-43.29]) tested positive for APLA, of whom 10 (33.3%; 95% CI [17.94-52.86]) had more than one APLA positivity. Anti-phosphatidylserine IgM positivity was described in 5.4% of inpatients (n = 5) and was associated with the occurrence of COVID-19-related thrombosis (p = 0.046). Anti-cardiolipin IgM positivity was the most prevalent among the inpatients (n = 12, 13.0%) and was associated with a recorded thrombosis in their clinical history (p = 0.044); however, its positivity was not associated with the occurrence of thrombosis during their hospitalisation for COVID-19. Anti-phosphatidylinositol IgM positivity, with a prevalence of 5.4% (n = 5), was associated with higher levels of interleukin (IL)-6 (p = 0.007) and ferritin (p = 0.034). Neither of these APLA positivities was a risk factor for COVID-19 severity or a predictive marker for long COVID-19. In conclusion, almost a third of COVID-19 inpatients tested positive for at least one APLA. Anti-phosphatidylserine positivity in IgM class was associated with thrombosis, and anti-phosphatidylinositol positivity in IgM class was associated with inflammation, as noticed by elevated levels of IL-6. Thus, testing for non-criteria APLA to assess the risk of clinical complications in hospitalised COVID-19 patients might be beneficial. However, they were not related to disease severity or long COVID-19.

Antiphospholipid Syndrome: State of the Art of Clinical Management

Antiphospholipid syndrome (APS) is a systemic autoimmune disorder clinically characterized by recurrent arterial and venous thrombosis and/or pregnancy morbidity in the presence of antiphospholipid antibodies. Currently, treatment is mainly focused on anticoagulation, but therapies targeting mechanisms involved in APS autoimmune pathogenesis could play an important role in specific settings. An evidence-based therapeutic approach is limited by the broad clinical spectrum of the syndrome and the nature of a "rare disease" that makes it difficult to carry out well-designed prospective studies. Vitamin K antagonists (AVK), notably warfarin, are the standard treatment for preventing recurrent venous thrombosis and perhaps also arterial thrombosis. Direct oral anticoagulants (DOACs) are not recommended at least in patients with triple positivity APS. Treatment options for the prevention of pregnancy complications in obstetric APS, as combined use of aspirin and heparin, low-dose prednisolone, hydroxychloroquine, intravenous immunoglobulin (IVIG), may improve pregnancy outcome. The catastrophic antiphospholipid syndrome (CAPS) is the most severe form of APS with acute multiple organ involvement and small vessel thrombosis. Glucocorticoids, heparin, plasma exchange or IVIG, rituximab, or eculizumab must be added to concurrent treatment of precipitating factors (e.g. infections) as rescue therapies. Finally, it has been observed that SARS COV2 infection may produce vascular complications mimicking the clinical and pathophysiological features of APS and particularly of CAPS. From this point of view, attention has been focused on the "protective" role of anticoagulant therapy in preventing thrombotic complication when these clinical conditions coexist.

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.

Antibodies to Domain I β2-Glycoprotein 1 in Patients with Antiphospholipid Syndrome and Systemic Lupus Erythematosus

The role of antiphospholipid antibodies (aPL), which are not included in the Sydney diagnostic criteria, in antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE) is poorly understood. The aim of this study was to determine the clinical significance of IgG antibodies for domain 1 of β2-glycoprotein 1 (β2-GP1), IgG anti-β2-GP1DI, in patients with APS with and without SLE. The study included 187 patients with APS with or without SLE, 49 patients formed the comparison group, and 100 apparently healthy individuals formed the control group. IgG/IgM antibodies to cardiolipin (aCL) and IgG/IgM anti-β2-GP1 were determined by enzyme immunoassay (ELISA) in patients with or without APS, and IgG anti-β2-GP1DI was determined by chemiluminescence assay (CLA) in all patients and controls. IgG anti-β2-GP1DI was detected in 37 (71%) of 52 patients with primary APS (PAPS), in 6 (50%) of 12 patients with probable APS, in 42 (71%) of 59 patients with SLE + APS, in 17 (26%) of 64 patients with SLE, in 1 (2%) of the comparison group, and in none of the control group. IgG anti-β2-GP1DI was significantly associated with PAPS and SLE + APS compared with the patients with SLE (p = 0.0002 and 0.0001, respectively). The association of IgG anti-β2-GP1DI with clinical manifestations of APS (thrombosis (p = 0.001) and obstetric pathology (p = 0.04)) was detected. There was a significant association of IgG anti-β2-GP1DI with arterial thrombosis (p = 0.002) and with late gestational obstetric pathology (p = 0.01). High specificity of IgG anti-β2-GP1DI depending on the diagnosis and clinical manifestations of APS despite low sensitivity was noted: specificity was 84% for thrombosis, 94% for obstetric pathology, and 89% for APS. Isolated IgG anti-β2-GP1DI positivity was reported in 2% of 50 aPL-negative patients and was not associated with APS manifestations. The frequency of IgG anti-β2-GP1DI detection was higher in the patients with APS compared to the patients with SLE, comparison group, and control (p < 0.05). Positive IgG anti-β2-GP1DI values were significantly associated with thrombotic complications and with obstetric pathology (p = 0.002 and p = 0.01, respectively). Specificity of IgG anti-β2-GP1DI for APS and its clinical manifestations (thrombosis and obstetric pathology) was higher than sensitivity (89, 94, and 84%, respectively).

The Diagnostics and Treatment of Recurrent Pregnancy Loss

Recurrent pregnancy loss is a common problem in the reproductive age population of women. It can be caused by many different conditions. This problem is addressed in international guidelines that take a slightly different approach to its diagnosis and treatment. The guidelines used in this review mainly use the guidelines of the Royal College of Obstetricians and Gynaecologists (RCOG), American Society of Reproductive Medicine (ASRM) and European Society of Human Reproduction and Embryology (ESHRE). This review shows how much the approach to miscarriages has changed and how much more needs to be explored and refined. The review also addresses the topic of unexplained pregnancy loss, which continues to be a challenge for clinicians.

Antiphospholipid syndrome management: a 2023 update and practical algorithm-based approach

PURPOSE OF REVIEW

Antiphospholipid syndrome (APS) is an acquired thrombo-inflammatory disease that has morbid and sometimes devastating effects on patients and their families. This review will discuss the most recent international societal treatment guidelines and propose practical management algorithms for various APS sub-types.

RECENT FINDINGS

APS represents a disease spectrum. Although thrombosis and pregnancy morbidities are traditional hallmarks of APS, a variety of extra-criteria clinical phenotypes can often be seen, which makes clinical management more challenging. Primary APS thrombosis prophylaxis should take a risk-stratified approach. Although vitamin K antagonists (VKAs) or heparin/low molecular weight heparin (LMWH) remain the preferred treatment for secondary APS thrombosis prophylaxis, some international society guidelines support the use of direct oral anticoagulants (DOACs) in certain circumstances. Careful monitoring and individualized obstetric care with the use of aspirin and heparin/LMWH will improve pregnancy outcomes among pregnant individuals with APS. Treatment of microvascular and catastrophic APS remains challenging. While the addition of various immunosuppressive agents is often utilized, further systemic evaluations of their use are warranted before definitive recommendations can be made. Several new therapeutic strategies are on the horizon that might enable more personalized and targeted APS management in the near future.

SUMMARY

Although the knowledge of APS pathogenesis has grown in recent years, the management principles and strategies are largely unchanged. There is an unmet need for evaluating pharmacological agents, beyond anticoagulants, that target diverse thromboinflammatory pathways.

Lupus anticoagulant laboratory diagnosis by applying the 2020 ISTH-SSC guidelines

BACKGROUND

The ISTH-SSC guidelines for lupus anticoagulant (LA) testing recommend using in-house determined cut-off values, pooled normal plasma (PNP) for ratio normalization, and a ratio for the mixing test interpretation. They strongly support the mixing step role in the diagnostic process.

OBJECTIVES

To investigate and compare the LA testing results and interpretations obtained following the ISTH-SSC guidelines or the available alternatives.

PATIENTS/METHODS

Blood samples for LA testing from 462 consecutive patients were evaluated for screening, mixing and confirmatory tests. The analysis focused on the interpretation differences between using (1) the in-house cut-off values versus the manufacturer's cut-off values, (2) a normalized ratio calculated using PNP at each run versus the mean of the reference interval, (3) a normalized ratio versus the index of circulating anticoagulant to interpret the mixing step, and (4) a two-step versus three-step procedure.

RESULTS

LA testing outcomes were comparable when using the in-house and manufacturer's cut-off values. More positive dilute Russell's viper venom (DRVV) time results were obtained with the normalized ratio based on PNP than with the mean of the reference interval. Overall, the mixing test results obtained with the normalized ratio and the index of circulating anticoagulant showed a good agreement. Among the 97 DRVV Screen test-positive samples, 33 and 89 were classified as LA-positive with the 3-step and the 2-step procedure, respectively.

CONCLUSIONS

The cut-off value used and the way to normalize ratios had a limited impact. Conversely, it is important to understand the mixing test characteristics to maximize its diagnostic potential.

Evolution of Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is an autoimmune prothrombotic disease characterized by thrombosis and/or pregnancy complications caused by antiphospholipid antibodies (aPL). The history of APS can be traced back to observations made during screening programs for syphilis conducted in the mid-20th century, with identification of patients with the so-called biological false-positive serological reactions for syphilis. Initial observation linking aPL with recurrent miscarriages was first reported more than 40 years ago. Since then, our understanding of the pathogenesis and management of APS has evolved markedly. Although APS is an autoimmune disease, anticoagulation mainly with vitamin K antagonists (VKAs) rather than immunomodulation, is the treatment of choice for thrombotic APS. Direct acting oral anticoagulants are inferior to VKAs, especially those with triple-positive APS and arterial thrombosis. Inflammation, complement activation, and thrombosis in the placenta may contribute to pathogenesis of obstetric APS. Heparin, mainly low-molecular-weight heparin, and low-dose aspirin represent the treatments of choice for women with obstetric complications. Increasingly, immunomodulatory agents such as hydroxychloroquine for thrombotic and obstetric APS are being used, especially in patients who are refractory to present standard treatment.

B cell-derived anti-beta 2 glycoprotein I antibody mediates hyperhomocysteinemia-aggravated hypertensive glomerular lesions by triggering ferroptosis

Hyperhomocysteinemia (HHcy) is a risk factor for chronic kidney diseases (CKDs) that affects about 85% CKD patients. HHcy stimulates B cells to secrete pathological antibodies, although it is unknown whether this pathway mediates kidney injury. In HHcy-treated 2-kidney, 1-clip (2K1C) hypertensive murine model, HHcy-activated B cells secreted anti-beta 2 glycoprotein I (β₂GPI) antibodies that deposited in glomerular endothelial cells (GECs), exacerbating glomerulosclerosis and reducing renal function. Mechanistically, HHcy 2K1C mice increased phosphatidylethanolamine (PE) (18:0/20:4, 18:0/22:6, 16:0/20:4) in kidney tissue, as determined by lipidomics. GECs oxidative lipidomics validated the increase of oxidized phospholipids upon Hcy-activated B cells culture medium (Hcy-B CM) treatment, including PE (18:0/20:4 + 3[O], PE (18:0a/22:4 + 1[O], PE (18:0/22:4 + 2[O] and PE (18:0/22:4 + 3[O]). PE synthases ethanolamine kinase 2 (etnk2) and ethanolamine-phosphate cytidylyltransferase 2 (pcyt2) were increased in the kidney GECs of HHcy 2K1C mice and facilitated polyunsaturated PE synthesis to act as lipid peroxidation substrates. In HHcy 2K1C mice and Hcy-B CM-treated GECs, the oxidative environment induced by iron accumulation and the insufficient clearance of lipid peroxides caused by transferrin receptor (TFR) elevation and down-regulation of SLC7A11/glutathione peroxidase 4 (GPX4) contributed to GECs ferroptosis of the kidneys. In vivo, pharmacological depletion of B cells or inhibition of ferroptosis mitigated the HHcy-aggravated hypertensive renal injury. Consequently, our findings uncovered a novel mechanism by which B cell-derived pathogenic anti-β₂GPI IgG generated by HHcy exacerbated hypertensive kidney damage by inducing GECs ferroptosis. Targeting B cells or ferroptosis may be viable therapeutic strategies for ameliorating lipid peroxidative renal injury in HHcy patients with hypertensive nephropathy.

Antiphospholipid Syndrome in Pregnancy: New and Old Pathogenetic Mechanisms

The antiphospholipid syndrome (APS) is a systemic autoimmune disorder characterized, according to the Sydney criteria, by the persistent presence of autoantibodies directed against phospholipid-binding proteins associated with thrombosis and/or obstetrical complications. The most frequent complications in obstetric antiphospholipid syndrome are recurrent pregnancy losses and premature birth due to placental insufficiency or severe preeclampsia. In recent years, vascular APS (VAPS) and obstetric APS (OAPS) have been described as two different clinical entities. In VAPS, antiphospholipid antibodies (aPL) interfere with the mechanisms of coagulation cascade and the 'two hit hypothesis' has been suggested to explain why aPL positivity does not always lead to thrombosis. OAPS seems to involve additional mechanisms, such as the direct action of anti-β2 glycoprotein-I on trophoblast cells that can lead to a direct placental functional damage. Furthermore, new actors seem to play a role in the pathogenesis of OAPS, including extracellular vesicles, micro-RNAs and the release of neutrophil extracellular traps. The aim of this review is to investigate the state-of-the-art antiphospholipid syndrome pathogenesis in pregnancy, in order to provide a comprehensive overview of both old and new pathogenetic mechanisms involved in this complex disease.

Antiphospholipid antibody-mediated NK cell cytotoxicity

Antiphospholipid syndrome (APS) is an autoimmune thrombophilia that is characterised by thrombosis and obstetric complications in the presence of antiphospholipid antibodies (aPL). Pregnancy complications remain a challenging problem for patients with APS, especially during the first trimester. Although natural killer (NK) cells constitute up to 70% of decidual lymphocytes during the first trimester, their contribution to early pregnancy loss in APS is largely unknown. We aimed to analyse whether aPL are able to recruit antibody-dependent cellular cytotoxicity (ADCC) of NK cells, with special emphasis on the differences in the effects of aPL containing anti-β2GPI domain 1 (anti-β2GPI-D1) antibodies (aPL+/D1+) and those that do not (aPL+/D1-). Our findings revealed a differential distribution of NK subsets in the presence of different aPL. Namely, aPL+/D1- IgGs increased CD56^dim/CD16^dim cells, while aPL+/D1 + IgGs increased the number of CD56^bright/CD16^dim cells. ADCC NK cell cytotoxicity was found to be higher in the presence of aPL+/D1- IgGs, as defined by an increased target cell death, degranulation and increased expression of CD11b, CD69 and NKG2D. Overall, our evidence showed that aPL are able to recruit ADCC, suggesting NK cells as candidate cells for APS-related obstetric complications.

Performance characteristics of 5 numerical indexes in mixing test interpretation under coexistence of lupus anticoagulant and coagulation factor deficiency

Background

The mixing test is useful to investigate the cause of unexpectedly prolonged activated partial thromboplastin time (APTT). Several indexes are available for distinguishing correction from non-correction (ie, factor deficiency from inhibitors), but their performance characteristics may differ because of their different formulas. Furthermore, it is unclear how each index performs under the coexistence of factor deficiency and inhibitors.

Objectives

The objective of this study was to examine the differences in indexes, depending on factor VIII activity (FVIII:C) levels and lupus anticoagulant (LA) titers in test samples.

Methods

APTT was measured in spiked samples with various FVIII:C levels and LA titers, normal pooled plasma (NPP), and their 4:1, 1:1, and 1:4 mixtures. The following 5 indexes were calculated: index of circulating anticoagulant, mixing test normalized ratio, 4:1 and 1:1 percent corrections, and an APTT difference between the 1:1 mixture and NPP. The samples with LA, showing correction, were measured for FVIII:C in a one-stage assay to check parallelism.

Results

All indexes showed correction under FVIII deficiency and non-correction under higher LA titers. However, under lower LA titers, some indexes showed non-correction but others showed correction because of dilution effects and variations in formulas and/or sample mix ratios. The differences among the indexes were more pronounced under coexistent FVIII deficiency and LA, even though LA titers were equal in the tested samples; samples with lower FVIII:C showed correction, whereas those with normal FVIII:C showed non-correction. The samples tested for FVIII:C showed non-parallelism.

Conclusion

Each index had different performance characteristics to LA samples, which were pronounced under low FVIII:C levels in test samples.

Advances in the Pathophysiology of Thrombosis in Antiphospholipid Syndrome: Molecular Mechanisms and Signaling through Lipid Rafts

The pathological features of antiphospholipid syndrome (APS) are related to the activity of circulating antiphospholipid antibodies (aPLs) associated with vascular thrombosis and obstetric complications. Indeed, aPLs are not only disease markers, but also play a determining pathogenetic role in APS and exert their effects through the activation of cells and coagulation factors and inflammatory mediators for the materialization of the thromboinflammatory pathogenetic mechanism. Cellular activation in APS necessarily involves the interaction of aPLs with target receptors on the cell membrane, capable of triggering the signal transduction pathway(s). This interaction occurs at specific microdomains of the cell plasma membrane called lipid rafts. In this review, we focus on the key role of lipid rafts as signaling platforms in the pathogenesis of APS, and propose this pathogenetic step as a strategic target of new therapies in order to improve classical anti-thrombotic approaches with "new" immunomodulatory drugs.

Antiphospholipid antibodies in chronic thromboembolic pulmonary hypertension

Acquired thrombophilia and in particular the presence of antiphospholipid antibodies (aPL) may play an important role in the development of chronic thromboembolic pulmonary hypertension (CTEPH). Young patients suffering from an episode of unprovoked pulmonary embolism (PE), or PE provoked by mild risk factors, should be tested for aPL. In case of a positive result, they should be closely followed up and lifelong anticoagulant treatment should be considered. Indeed, aPL-induced thrombophilia may favor PE recurrence with the consequence of possible CTEPH development. The aPL profiles play an important role in this pathway. Patients with PE and triple positivity (lupus anticoagulant, LAC, anti-cardiolipin, aCL, and anti-β2-glycoprotein I, aβ2GPI) are at the highest risk of recurrence and deserve maximum protection by anticoagulant treatment with warfarin.