Antiphospholipid syndrome: laboratory detection, mechanisms of action and treatment

Connective tissue disease as a challenge in heart failure: Three case reports

RATIONALE

Connective tissue disease (CTD) is a heterogeneous group of chronic inflammatory autoimmune disorders derived from a systemically auto-immunological deregulation. CTD may affect cardiac structures through multiple pathophysiological mechanisms, and subclinical cardiac injury is common. Heart failure (HF) is one of the common complications in these patients.

PATIENT CONCERNS

Patients with CTD suffer an increased risk of cardiovascular disease and may have chest pain and shortness of breath.

DIAGNOSIS

HF is characterized by dyspnea or exertional limitation due to impaired ventricular filling and/or blood ejection. HF can be caused by other systemic diseases, not only by cardiovascular disorders but CTD. CTD may cause HF due to diffuse myocardial damage, heart valve damage, coronary ischemia, and so on.

INTERVENTIONS

The patient with catastrophic antiphospholipid syndrome take prednisone and warfarin. The patient with anti-synthetase syndrome was treated with immunoglobulin, followed by long-term oral medicines of prednisone, methotrexate, and folic acid.

OUTCOMES

The symptoms of chest pain and shortness of breath for patients with CTD improved.

LESSONS

HF is one of the common complications in these patients with CTD, which has poor prognosis and severe aggravation. Once such patients experience chest pain, chest tightness, shortness of breath, etc, we should consider the possibility of HF. Early identification and correct treatment can delay the progression of HF, improve the prognosis, and enhance the quality of life for patients. Therefore, we should pay more attention to patients with CTD combined with HF.

Lupus Anticoagulant Detection under the Magnifying Glass

Diagnosis of antiphospholipid syndrome (APS) requires the presence of a clinical criterion (thrombosis and/or pregnancy morbidity), combined with persistently circulating antiphospholipid antibodies (aPL). Lupus anticoagulant (LA) is one of the three laboratory parameters (the others being antibodies to either cardiolipin or β2-glycoprotein I) that defines this rare but potentially devastating condition. For the search for aCL and aβ2-GP-I, traditionally measured with immunological solid-phase assays (ELISA), several different assays and detection techniques are currently available, thus making these tests relatively reliable and widespread. On the other hand, LA detection is based on functional coagulation procedures that are characterized by poor standardization, difficulties in interpreting the results, and interference by several drugs commonly used in the clinical settings in which LA search is appropriate. This article aims to review the current state of the art and the challenges that clinicians and laboratories incur in the detection of LA.

SARS-CoV-2 infection and SLE: endothelial dysfunction, atherosclerosis, and thrombosis

An increased risk of atherosclerotic and thrombotic complications characterizes connective tissue diseases. Endothelial dysfunction is the basis for the initiation and progression of atherosclerosis and thrombosis. We present systemic lupus erythematosus (SLE) as a model rheumatic disease with endothelial dysfunction and discuss its mechanisms, factors that influence the early onset and rapid progression of atherosclerosis, and the increased risk of thromboembolic events. We focus on established methods to improve endothelium function, including statins, antiplatelet, and antithrombotic therapy. Hypercoagulable and hypofibrinolitic states and a hyperinflammatory response characterize severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Several pathogenic mechanisms are typical for an acute phase of Covid-19 post-Covid syndrome and connective tissue diseases: endothelial dysfunction, elevated antiphospholipid antibody titer, activation of the complement system, and formation of extracellular neutrophil traps (NET). The current review discusses the mechanisms underlying SLE and the COVID-19 in the context of endothelial function, atherosclerosis, and thrombosis (Graphical abstract). Key Points • The pathophysiology of systemic lupus erythematosus (SLE) and Covid-19 shows some similarities, such as endothelial cell activation and dysfunction, the activation of complementary systems, the presence of antiphospholipid antibodies, and the formation of extracellular neutrophil traps. • Autoimmunity in both diseases creates the basis for hyperinflammatory, hypercoagulable, and hypofibrinolitic states and their thromboembolic complications. • This paper presents our perspective on the mechanisms behind the cardiovascular manifestations of SLE and COVID-19, with a particular emphasis on endothelial dysfunction. Covid-19 and systemic lupus erythematosus-potential similarities in pathophysiology. Figures of the panel illustrate the clinical manifestations of endothelial dysfunction, atherosclerosis, and thromboembolism, including coronary artery disease ([A] coronary angiography with left anterior descending artery stenosis and [B] scintigraphy with reduced perfusion in the myocardial apical segments), stroke ([C] carotid angiography, left carotid artery occlusion) and pulmonary embolism ([D]computed tomography with thrombus in the right pulmonary artery).

Thromboplastin calibration revisited to look for possible revision of the World Health Organization recommendations

BACKGROUND

Thromboplastin calibration is essential to determine the international sensitivity index required to calculate the international normalized ratio (INR). The procedure for calibration recommended by the World Health Organization (WHO) calls for the selection of patients on stable anticoagulation in the range of 1.5 to 4.5 INR. These patients are difficult to be recruited as the conventional therapeutic interval for warfarin is 2.0 to 3.0. A possible solution could be including patients with less intense anticoagulation in the calibration.

OBJECTIVES

We sought to investigate the impact of this amended procedure on the parameters of calibration.

METHODS

Eight data sets from previous calibrations of a rabbit thromboplastin that included patients on anticoagulation as required by WHO were used for this pilot study. Parameters of calibration as determined by the full data sets are identified as "full calibrations" and are considered reference. Each of the data sets were used to recalculate the calibration parameters after including patients with INRs of <4.0, <3.5, or <3.0, which were identified as "trimmed calibrations" and compared with those from the full calibrations.

RESULTS

There was marginal variation of the international sensitivity index, CV, and INR that can be hardly of practical significance. CV was the most affected parameter, which increased from the full to the trimmed <3.0 calibration, but never exceeded the 3% cutoff value recommended by WHO.

CONCLUSIONS

Should the results of this pilot study be confirmed for the calibration of other thromboplastins, revision of the WHO recommendations to include patients with INR from 1.5 to 4.0 is warranted.

Arterial stiffness and atherosclerosis in systemic lupus erythematosus patients

Introduction

Systemic lupus erythematosus (SLE) is characterized by early atherothrombosis. Pulse wave velocity (PWV) is a promising tool for the diagnosis of early vascular remodelling and initial atherosclerotic plaque formation. Our objective was to evaluate PWV and its relationship with coronary atherosclerosis and thrombotic biomarkers in patients with SLE.

Material and methods

In 26 patients with SLE with stable clinical conditions, mean age of 39.1 ±11.7 years and without a history of coronary artery disease, multidetector computed tomography (MDCT)-based coronary calcium scoring (CACS) was performed and PWV measured.

Laboratory evaluation included serum levels of anticardiolipin and anti-β2-glycoprotein antibodies (anti-β2-GPI), lupus anticoagulant (LA), D-dimers, thrombin–antithrombin complexes (TAT), and von Willebrand factor (vWF).

Results

Multidetector computed tomography revealed coronary calcifications in 8 (30.8%) patients and the median CACS was 52.4 HU (range 2–843.2). The mean PWV was 9.0 ±3.2 m/s and was higher in patients aged > 50 years (+33.7% vs. < 50 years), those with positive LA (+28.2% vs. LA negative), TAT ≥ 10 μg/l (+18.1% vs. < 10 μg/l), vWF ≥ 200 IU/dl (+51.8% vs. < 200 IU/dl) and with coronary atherosclerosis (CACS > 0; +21.4% vs. CACS = 0).

In contrast, the duration of the disease, D-dimers, anticardiolipin, and anti-β2-GPI antibodies did not influence PWV. In the group without atherosclerosis (CACS = 0, n =18), patients with vWF ≥ 200 IU/dl had a 19.3% higher PWV compared to the rest.

Conclusions

In patients with SLE, PWV was associated with the presence of coronary atherosclerotic lesions in MDCT. Furthermore, arterial stiffness was higher in patients with markers of endothelial dysfunction and a prothrombotic state, suggesting their contribution to the early stages of arterial remodelling in SLE.

Direct oral anticoagulants versus vitamin K antagonists in patients with antiphospholipid syndrome: systematic review and meta-analysis

Background

Despite vitamin K antagonists (VKA) being the gold standard in the prevention of thromboembolic events in antiphospholipid syndrome (APS), non-vitamin K antagonists oral anticoagulants/direct oral anticoagulants (DOACs) have been used off-label.

Objective

We aimed to perform a systematic review comparing DOACs to VKA regarding prevention of thromboembolic events, occurrence of bleeding events and mortality in patients with APS.

Methods

An electronic database search was performed through MEDLINE, CENTRAL and Web of Science. After data extraction, we pooled the results using risk ratio (RR) and 95% CI. Heterogeneity was assessed using the I². The outcomes considered were all thromboembolic events as primary, and major bleeding, all bleeding events and mortality as secondary. Evidence confidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation methodology.

Results

We included 7 studies and a total of 835 patients for analyses. Thromboembolic events were significantly increased in DOACs arm, compared with VKA—RR 1.69, 95% CI 1.09 to 2.62, I²—24%, n=719, 6 studies. In studies using exclusively rivaroxaban, which was the most representative drug in all included studies, the thromboembolic risk was increased threefold (RR 3.36, 95% CI 1.53 to 7.37). The risks of major bleeding, all bleeding events and mortality were not significantly different from control arm. The grade of certainty of our results is very low.

Conclusions

Current evidence suggests DOACs use, particularly rivaroxaban, among patients with APS, is less effective than VKA since it is associated with 69% increased risk of thromboembolic events.

Trial registration number

CRD42020216178.

Diagnostic Challenges on the Laboratory Detection of Lupus Anticoagulant

Lupus anticoagulant (LA) is one of the three laboratory parameters (the others being antibodies to either cardiolipin or β2-glycoprotein I) which defines the rare but potentially devastating condition known as antiphospholipid syndrome (APS). Testing for LA is a challenging task for the clinical laboratory because specific tests for its detection are not available. However, proper LA detection is paramount for patients’ management, as its persistent positivity in the presence of (previous or current) thrombotic events, candidate for long term anticoagulation. Guidelines for LA detection have been established and updated over the last two decades. Implementation of these guidelines across laboratories and participation to external quality assessment schemes are required to help standardize the diagnostic procedures and help clinicians for appropriate management of APS. This article aims to review the current state of the art and the challenges that clinical laboratories incur in the detection of LA.

Anti-phospholipid syndrome and COVID-19 thrombosis: connecting the dots

As the coronavirus disease 2019 (COVID-19) pandemic, which is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is spreading rapidly worldwide, it has emerged as a leading cause of mortality, resulting in >1 million deaths over the past 10 months. The pathophysiology of COVID-19 remains unclear, posing a great challenge to the medical management of patients. Recent studies have reported an unusually high prevalence of thromboembolic events in COVID-19 patients, although the mechanism remains elusive. Several studies have reported the presence of aPLs in COVID-19 patients. We have noticed similarities between COVID-19 and APS, which is an autoimmune prothrombotic disease that is often associated with an infective aetiology. Molecular mimicry and endothelial dysfunction could plausibly explain the mechanism of thrombogenesis in acquired APS. In this review, we discuss the clinicopathological similarities between COVID-19 and APS, and the potential role of therapeutic targets based on the anti-phospholipid model for COVID-19 disease.

Combined brain/heart magnetic resonance imaging in antiphospholipid syndrome-two sides of the same coin

Antiphospholipid syndrome (APS) is an autoimmune disorder characterized by arterial, venous, and/or small vessel thrombosis, pregnancy morbidity, and persistently elevated levels of antiphospholipid antibodies (aPL). Cardiovascular disease (CVD) in APS can present as heart valvular disease (HVD), macro-micro-coronary artery disease (CAD), myocardial dysfunction, cardiac thrombi, or pulmonary hypertension. Brain disease presents as stroke or transient ischemic attack (TIA) and less frequently as cerebral venous thrombosis, seizures, cognitive dysfunction, multiple sclerosis (MS)-like syndrome, or chorea. Infarcts and focal white matter hyperenhancement are the commonest brain (MRI) abnormalities, while myocardial ischemia/fibrosis, valvular stenosis/regurgitation, or cardiac thrombi are the main abnormalities detected by cardiovascular magnetic resonance. This review aims to present the existing evidence on brain/heart involvement and their interrelationship in APS and the role of brain/heart MRI in their evaluation. Embolic brain disease, due to HVD, CAD, and/or cardiac thrombus, or brain hypo-perfusion, due to myocardial dysfunction, are among the main brain/heart interactions in APS and they are considered determinants of morbidity and mortality. Currently, there is no evidence to support the use of combined brain/heart MRI in asymptomatic APS patients. Until more data will be available, this approach may be considered in APS patients at high risk for CVD/stroke, such as systemic lupus erythematosus with high-risk aPL profile or high scores in CVD risk prediction models; APS patients with HVD/thrombus, CAD, or heart failure; those with classic and non-criteria neurologic APS manifestations (seizures, cognitive dysfunction, MS-like syndrome); or with aggressive multi-organ disease. Key Points • Cardiovascular disease (CVD) in antiphospholipid syndrome (APS) can present as heart valvular disease (HVD), macro-micro-coronary artery disease (CAD), myocardial dysfunction, cardiac thrombi, or pulmonary hypertension. • Brain disease presents as stroke or transient ischemic attack (TIA), and less frequently as cerebral venous thrombosis, seizures, cognitive dysfunction, and multiple sclerosis (MS). • A combined brain/heart MRI may be considered in APS patients at high risk for CVD/stroke, such as systemic lupus erythematosus with high-risk aPL profile or high scores in CVD risks; APS patients with HVD/thrombus, CAD, or heart failure; those with classic and non-criteria neurologic APS manifestations (seizures, cognitive dysfunction, MS-like syndrome); or with aggressive multi-organ disease.

Lupus anticoagulant detection in anticoagulated patients. Guidance from the Scientific and Standardization Committee for lupus anticoagulant/antiphospholipid antibodies of the International Society on Thrombosis and Haemostasis

BACKGROUND

The laboratory detection of lupus anticoagulants (LA) in anticoagulated patients represents a challenge and there is no consensus on the types of assays/procedures to be adopted.

OBJECTIVES

This communication of the International Society on Thrombosis and Haemostasis (ISTH), Scientific and Standardization Committee (SSC) aims to give guidance on the procedures to be adopted.

METHODS

Members of the ISTH-SSC on Lupus Anticoagulant/Antiphospholipid Antibodies reviewed the literature to search for evidence on the most appropriate assays/procedures to be adopted.

RESULTS

Anticoagulants are able to interfere with the tests used for LA detection, giving rise to occasional false-positive or false-negative LA. Some commercial tests include in their composition heparin-neutralizers able to quench unfractionated or low molecular weight heparin up to 1.0 U/mL. LA tests are less affected by low molecular weight heparin, but caution is needed in the interpretation of results. Vitamin K antagonists (VKAs) may affect LA detection. Dilution of test plasma into pooled normal plasma is not a reliable solution as false-negative or false-positive LA may occur. Direct oral anticoagulants (DOACs) affect LA detection. Hence, it is not recommended to attempt LA detection in those patients. The use of DOAC adsorbents is a promising solution and should be further investigated on LA-positive and LA-negative patient populations. Taipan/Ecarin tests may be a solution for VKAs and anti-FXa DOACs, but independent evidence on their value and standardized kits is needed.

CONCLUSIONS

LA detection during anticoagulation remains a challenge, especially for VKAs. DOAC removal by in vitro addition to plasma of appropriate absorbents is promising.

Anticardiolipin from Periodontitis Patients Impact Fetal Loss and Annexin V

Anticardiolipin antibodies, found at elevated serum concentrations in 15% to 20% of individuals with periodontitis, are associated with adverse pregnancy outcomes, thrombotic conditions, and accelerated atherosclerosis in autoimmune disease such as the antiphospholipid syndrome. Our previous studies demonstrated that antibodies raised in mice against Porphyromonas gingivalis caused fetal loss in a mouse pregnancy model due to anticardiolipin antibodies. Such antibodies are induced via molecular mimicry with the serum protein β2-glycoprotein 1 (β2GP1), the target antigen of anticardiolipin. Furthermore, human anticardiolipin IgG is associated with increased serum markers of vascular inflammation, and IgG purified from periodontitis subjects with elevated anticardiolipin stimulates inflammatory cytokine production by endothelial cells and a trophoblastic cell line. Activation of the trophoblastic cells by anticardiolipin occurs through Toll-like receptor 4. In the present study, we observed that IgG anticardiolipin from periodontitis subjects also causes fetal loss in mice. Displacement of the protective 2-dimensional lattice formed by annexin V on trophoblast surfaces by anticardiolipin, via its interaction with its target antigen β2GP1, leading to fibrin clot formation due to exposure of anionic phospholipids to plasma, is a plausible pathogenic mechanism explaining adverse obstetrical outcomes in antiphospholipid syndrome. Therefore, we assessed such interactions in periodontitis. We observed that anticardiolipin from periodontitis subjects competes for annexin V on an artificial phosphatidylserine monolayer, replicating a key activity of autoantibodies found in patients with antiphospholipid syndrome. In addition, we found that anticardiolipin from periodontitis subjects increases annexin V levels on the BeWo choriocarcinoma cell line, consistent with mobilization of annexin V to the cell surface to facilitate repair following membrane damage. The data indicate that sera and IgG from periodontitis subjects with elevated anticardiolipin levels may influence pregnancy outcomes due to interactions with annexin V.

The effect of DOAC-Stop on lupus anticoagulant testing in plasma samples of venous thromboembolism patients receiving direct oral anticoagulants

Background

Direct oral anticoagulants (DOACs) cause false positive lupus anticoagulant (LA) results. We assessed the impact of DOAC-Stop, reversing in vitro effects of DOACs, on LA testing in anticoagulated patients.

Methods

We assessed 75 venous thromboembolism patients aged 44.5±14.6 years. Blood samples were collected 2–28 h since intake of DOACs, including 50 patients on rivaroxaban, 20 on dabigatran and five on apixaban. LA testing was performed at baseline and after DOAC-Stop treatment. Positive LA was defined as the normalized (patient/standard plasma clotting time) LA screening and screening (LA1)/confirmation (LA2) ratios exceeding 1.2.

Results

LA diluted Russell’s viper venom time (dRVVT) normalized screening test revealed abnormal results in 73 (97.3%) and activated partial thromboplastin time (APTT)-LA in 49 (65.3%) patients. In six (8%) patients, antiphospholipid syndrome (APS) was diagnosed. dRVVT LA1/LA2 was abnormal in 35 (50.7%) patients taking DOACs. The APTT ratio was normal in all studied subjects. DOAC-Stop completely removed dabigatran and reduced by 98% rivaroxaban and by 92.3% apixaban concentrations (all p<0.05). After DOAC-Stop screening dRVVT remained prolonged in 34 (49.3%) patients (p<0.001), while dRVVT LA1/LA2 was abnormal in six (8.7%) subjects, with no association with DOAC concentrations at baseline and after DOAC-Stop. The APTT-LA screening test remained prolonged in five (7.2%) patients, while the APTT LA1/LA2 ratio was normal in those subjects. DOAC-Stop did not influence LA testing in APS patients.

Conclusions

Application of DOAC-Stop effectively reduced plasma DOAC concentrations leading to appropriate dRVVT results in up to 97% of VTE patients.

Unfavourably altered plasma clot properties in patients with primary Raynaud's phenomenon: association with venous thromboembolism

Associations of Raynaud’s phenomenon (RP) with venous thromboembolism (VTE) are unclear. We investigated the occurrence of RP together with prothrombotic state markers and fibrin clot properties in VTE patients. In this prospective cohort study we enrolled 360 patients free of known autoimmune disease. D-dimer, von Willebrand factor (vWF), plasma clot permeability (K_s), clot lysis time (CLT) along with fibrinolysis activators and inhibitors were determined at least 3 months since the VTE event. The presence/absence of RP was diagnosed at least 6 months before VTE. Primary RP occurred in 57 subjects (17%) with a 3.6-fold higher prevalence among women. Patients with RP had 11% higher fibrinogen, 16% higher vWF, 5% lower K_s, and 10% longer CLT (all p < 0.05). Females with RP (21%) had 6.6% lower K_s, 11.2% longer CLT, and 18.5% higher vWF (all p < 0.05) compared with men. CLT was predicted by PAI-1 and vWF levels. Regression analysis showed that RP was a predictor of prolonged CLT in the whole patient group (OR 3.46, 95% CI 1.92–6.24) and in women following VTE (OR 2.75, 95% CI 1.31–5.78). Primary RP patients tend to form denser plasma fibrin clots displaying impaired lysability and increased endothelial damage. RP might be a novel risk factor for VTE, especially in women.

Cardiac Manifestations of Antiphospholipid Syndrome With Focus on Its Primary Form

Antiphospholipid syndrome (APS) is a multisystem autoimmune disease most commonly associated with recurrent arterial and venous thromboembolism and recurrent fetal loss. Other possible antiphospholipid antibody (aPL)-related clinical manifestations include cardiac involvement. The heart can be involved through immune mediated and /or thrombotic mechanisms. Mortality due to cardiovascular problems is elevated in APS. However, the cardiovascular risk in patients with primary APS (PAPS) compared with lupus-related APS is yet to be established. Cardiac symptoms of APS include valve abnormalities (thickening and vegetations), coronary artery disease (CAD), myocardial dysfunction, pulmonary hypertension, and intracardiac thrombi. Heart valve lesions are the most common cardiac manifestation, observed in approximately one third of PAPS patients and usually do not cause hemodynamic significance. Deposits of immunoglobulins including anticardiolipin (aCL), and of complement components, are commonly observed in affected heart valves from these patients. This suggests that an inflammatory process is initiated by aPL deposition, eventually resulting in the formation of valvular lesion. aPL may have a direct role in the atherosclerotic process via induction of endothelial activation. Multiple traditional and autoimmune-inflammatory risk factors are involved in triggering an expedited atherosclerotic arterial disease evident in APS. It is imperative to increase the efforts in early diagnosis, control of risk factors and close follow-up, in the attempt to minimize cardiovascular risk in APS. Clinicians should bear in mind that a multidisciplinary therapeutic approach is of paramount importance in these patients. This article reviews the cardiac detriments of APS, including treatment recommendations for each cardiac complication.

Diagnosis, Development, and Treatment of Portal Vein Thrombosis in Patients With and Without Cirrhosis

Portal vein thrombosis unrelated to solid malignancy is common in patients with cirrhosis, but less frequently observed in patients without cirrhosis. Prompt diagnosis and management of acute symptomatic portal vein thrombosis are essential. Failure to detect and treat thromboses can result in mesenteric ischemia, chronic cavernous transformation, and complications of portal hypertension. In patients with cirrhosis, development of portal vein thrombosis is often insidious and remains undetected until its incidental detection. Management of portal vein thrombosis in patients with cirrhosis is more controversial. However, there are data to support treatment of specific patients with anticoagulation agents. We review the common and distinct features of portal vein thromboses in patients without liver tumors, with and without cirrhosis.

Understanding the Unique Role of Phospholipids in the Lubrication of Natural Joints: An Interfacial Tension Study

Some solid lubricants are characterized by a layered structure with weak (van der Waals) inter-interlayer forces which allow for easy, low-strength shearing. Solid lubricants in natural lubrication are characterized by phospholipid bilayers in the articular joints and phospholipid lamellar phases in synovial fluid. The influence of the acid–base properties of the phospholipid bilayer on the wettability and properties of the surface have been explained by studying the interfacial tension of spherical lipid bilayers based on a model membrane. In this paper, we show that the phospholipid multi-bilayer can act as an effective solid lubricant in every aspect, ranging from a ‘corrosion inhibitor’ in the stomach to a load-bearing lubricant in bovine joints. We present evidence of the outstanding performance of phospholipids and argue that this is due to their chemical inertness and hydrophilic–hydrophobic structure, which makes them amphoteric and provides them with the ability to form lamellar structures that can facilitate functional sliding. Moreover, the friction coefficient can significantly change for a given phospholipid bilayer so it leads to a lamellar-repulsive mechanism under highly charged conditions. After this, it is quickly transformed to result in stable low-friction conditions.

Anti-β2-glycoprotein I and anti-phosphatidylserine/prothrombin antibodies exert similar pro-thrombotic effects in peripheral blood monocytes and endothelial cells

Purpose

The introduction of the anti-phosphatidylserine/prothrombin (aPS/PT) antibodies among the routinely investigated anti-phospholipid (aPL) antibodies led to an improvement in anti-phospholipid syndrome (APS) laboratory diagnostic performance; however, their pathogenic mechanism is still substantially undefined. To support clinical data and future inclusion as possible new criteria antibodies, we designed a head-to-head study to directly compare the procoagulant effects sustained in vitro by aPS/PT to those sustained by anti-β2-glycoprotein I (aβ2GpI) domain 1-specific antibodies.

Methods

Blood donors-derived monocytes and endothelial cells (HUVEC) were stimulated with lipopolysaccharides (LPS) alone or in combination with the IgG fractions isolated from the serum of six APS patients, positive only for aβ2GpI or for aPS/PT antibodies. As control, cells were incubated with LPS plus the IgG isolated from blood donors. Tissue factor (TF) mRNA expression was measured after four hours incubation by real-time PCR. Nitric oxide (NO) levels were measured in cells supernatant after 16 h incubation by colorimetric assay.

Results

aPS/PT and aβ2GpI IgG antibodies fractions showed comparable ability to enhance LPS-induced TF mRNA expression, either in monocytes and in HUVEC. Compared to LPS alone, we found that NO levels are strongly overproduced in HUVEC treated with LPS plus aβ2GpI and aPS/PT IgG fractions.

Conclusions

Our data support the significant and independent role of aPS/PT in the pathogenesis of the thrombotic events in APS patients, possibly adding new light to the therapeutic management of cases characterized by the sole presence of aPS/PT IgG antibodies.

Electronic supplementary material

The online version of this article (10.1186/s13317-019-0113-9) contains supplementary material, which is available to authorized users.

Natural joints: Boundary lubrication and antiphospholipid syndrome (APS)

The paper shows that osteoporosis (OA) changes the SF content and the lipid profile substantially. To estimate the implication of the lipid environment in case the articular cartilage (AC) changes, we measured friction coefficient normal samples, with early and late stages of (OA). During joint inflammation and osteoarthritis, enzymatically activated β₂-Glycoprotein I is transformed into antibody conformation. Our hypothesis about cartilage degradation of PL bilayers by antibodies (β₂-Glycoprotein I) is considering antiphospholipid syndrome (APS), which was not discussed in the literature before. Deactivated PL molecule has no ability to form bilayers, lamellar phases, and liposomes. The phospholipid content in synovial fluid (SF) during joint inflammation, osteoarthritis, and rheumatoid arthritis is significantly higher (2-3 times) above the normal concentration of PL, and has a poor boundary-lubricating ability is deactivated.

Rivaroxaban vs warfarin in high-risk patients with antiphospholipid syndrome

Publisher's Note: There is a Blood Commentary on this article in this issue.

Diagnostics and treatment of thrombotic antiphospholipid syndrome (APS): A personal perspective

Antiphospholipid Syndrome (APS) is a condition characterized by the occurrence of thromboembolic events and/or pregnancy loss combined with one laboratory criterion among Lupus Anticoagulant- LAC, anticardiolipin -aCL, and anti β2-Glycoprotein I -aβ2GPI antibodies. Several hypotheses were put forward to explain the causal role of antibodies in the clinical events but none is fully convincing. Current laboratory diagnosis is based on three tests (LAC, IgG/IgM aβ2GPI and IgG/IgM aCL antibodies). The triple-positive profile (all the three tests positive, same isotype) is associated with a higher risk for thrombosis. The mainstay of therapy in thrombotic APS is anticoagulation, with VKAs being the cornerstone. Low dose aspirin in combination or alone may have a role in arterial thrombosis, and in primary thromboprophylaxis. The Non-Vitamin K Antagonists Oral Anticoagulants (NOACs) role in the therapy of APS is under investigation but not verified. Alternative treatment options including rituximab and eculizumab have been successfully reported in few cases of catastrophic APS.

Classical and additional antiphospholipid antibodies in blood samples of ischemic stroke patients and healthy controls

Classical antiphospholipid antibodies (aPLa) are found in 6-25% of blood samples from stroke patients. The frequency of novel aPLa antibodies in blood samples of CVA patients is not known. Enzyme-linked immunosorbent assays (ELISA) were performed on blood samples from 209 CVA patients (170 samples were obtained during the acute phase and 39 samples were from patients with complete carotid stenosis) and compared to 54 healthy controls. Subjects were tested for the presence of the classical aPL antibodies anticardiolipin (aCL) and anti-beta2-glycoprotein (aβ2gI), in addition to antiphosphatidylethanolamine (aPE), anti-phosphatidylserine (aPS), and Annexin V. All antibodies were tested for both IgM and IgG subclasses. Numeric analysis of the antibody titer levels (μ/ml) revealed a significantly higher subclinical titer by two standard deviations of many aPL autoantibodies among CVA patients (Pv < 0.05). However, according to the kit manufacturer's cutoff value, no positive antibodies were found except a trend toward higher percentage of positive aPS IgG titer in the CVA group compared to controls (6.2 vs. %0; P = 0.077). According to the manufacturer's cutoff, significantly higher levels of positive antibodies were not found among stroke patients. However, the absolute ELISA values of stroke patients were significantly higher. These results suggest that lower cutoff values than those used for APS diagnosis should be used for risk stratification of CVA among healthy individuals.

Anti-phospholipid syndrome: Current opinion on mechanisms involved, laboratory characterization and diagnostic aspects

Anti-phospholipid syndrome is a complex and severe clinical situation, associated with symptoms such as recurrent thrombosis, arterial or venous, at any site, pregnancy loss, and other related syndromes. These clinical burdens, are highly variable from patient to patient, and are associated with biological abnormalities, such as the presence of the Lupus Anticoagulant or phospholipid dependent antibodies, confirmed on two occasions at least 12 weeks apart. From the diagnosis standpoint, both, functional (clotting) or immunological assays, are difficult to standardize and to optimize, due to the absence of reference material, or a characteristic clinical group, and international reference preparations. Large cohort studies are necessary for defining the usefulness of each assay, in terms of specificity, sensitivity, accuracy and for following-up the disease evolution. Clotting assays are based on Activated Partial Thromboplastin Time (APTT) and diluted Russell Viper Venom Time (dRVVT), performed at low and high phospholipid concentration, or on 1:1 mixtures of tested sample and a normal plasma pool. They allow evaluation of the paradoxal effects of LAs, which are pro-thrombotic in vivo, and anticoagulant in vivo. Use of synthetic phospholipids improves assay specificities and sensitivities, especially in patients treated with anticoagulants. Immunoassays can also be used for testing phospholipid dependent antibodies, first identified and measured as anti-cardiolipin antibodies, but now characterized as targeted to phospholipid cofactor proteins: mainly β2GP1 (which exposes cryptic epitopes upon binding to phospholipids), and in some cases prothrombin, and more rarely Protein S, Factor XIII, Protein Z or Annexin V. Use of optimized assays designed with well-characterized anionic phospholipids, then complexed with highly purified phospholipid cofactor protein (mainly β2GP1), offers a better link between reactivity and clinical associations, than the former assays which were empirically designed with cardiolipin. Standardization also remains complicated due to the absence of international standards and harmonized quantitation units. Validation on large cohorts of negative and positive patients remains the key approach for defining assay performance and clinical usefulness. Laboratory practice for all these methods is now greatly facilitated thanks to the use of automated instruments and dedicated software. Along with clinical criteria, laboratory assays are of great usefulness for identification and confirmation of the anti-phospholipid syndrome and they allow disease follow-up when appropriate patient management is in place.

Clinical and Prognostic Significance of Lupus Anticoagulant Measurement in Patients With Lung Cancer

Lupus anticoagulants is related to both recurrent thrombosis and cancer. Thrombotic complications occur more frequently in patients with lung cancer. The aim of this study is to investigate the association of lupus anticoagulants with hypercoagulability and thrombotic complications, as well as prognostic significance of lupus anticoagulants for patients with lung cancer. The study comprised 205 patients with non–small cell lung cancer. Plasma normalized LAC ratio, D-dimer, fibrinogen, activities of antithrombin, and FVIII before treatment were analyzed by coagulation analyzer, and routine hematologic and biochemical parameters were also evaluated. In patients, normalized LAC ratio, D-dimer, fibrinogen, and procoagulant activity of coagulating factor VIII levels significantly increased, whereas antithrombin activity significantly decreased compared with healthy controls (P < .001). Normalized LAC ratio was positively correlated with D-dimer, fibrinogen, and procoagulant activity of coagulating factor VIII, and negatively correlated with antithrombin activity, respectively (P < .01). D-dimer, procoagulant activity of coagulating factor VIII, and antithrombin levels revealed statistical difference in non–deep venous thrombosis patients with elevated or normal normalized LA ratio (P < .05). The incidence of deep venous thrombosis and tumor metastasis was higher, and 1-year survival rate was lower in elevated normalized LAC ratio patients than in normal ones, respectively (P < .01). There was higher normalized LAC ratio level in patients with deep venous thrombosis and/or metastasis (P < .05). In 1-year deceased patients, normalized LAC ratio level and the incidence of deep venous thrombosis and metastasis were higher than those in survivors, respectively (P < .05). Hazard regression analysis demonstrated normalized LAC ratio was independently associated with short survival time in patients with non–small cell lung cancer (hazard regression: 2.871, 95%confidence interval: 1.704-4.835; χ²: 19.130; P < .01). Our study suggests that lupus anticoagulants is a useful marker to predict thrombotic complications and prognosis in patient with lung cancer.

Variability of cut-off values for the detection of lupus anticoagulants: results of an international multicenter multiplatform study

Essentials Between-lab variations of cut-off values in lupus anticoagulant detection are unknown. Cut-off values were calculated in 11 labs each testing plasma from 120 donors with 3 platforms. Major variation was observed even within the same platform. Cut-off values determined in different labs are not interchangeable.

SUMMARY

Background Cut-off values for interpretation of lupus anticoagulant (LA) detection are poorly investigated. Aims (i) To assess whether results from healthy donors were normally distributed and (ii) the between-laboratories differences in cut-off values for screening, mixing and LA confirmation when calculated as 99th or 95th centiles, and (iii) to assess their impact on the detection rate for LA. Methods Each of 11 laboratories using one of the three widely used commercial platforms for LA detection was asked to collect plasmas from 120 healthy donors and to perform screening, mixing and LA confirmation with two methods (activated partial thromboplastin time [APTT] and dilute Russell viper venom [dRVV]). A common set of LA-positive or LA-negative freeze-dried plasmas was used to assess the LA detection rate. Results were centralized (Milano) for statistical analysis. Results and conclusions (i) Clotting times or ratios for healthy subjects were not normally distributed in the majority of cases. The take-home message is that cut-off values should be determined preferably by the non-parametric method based on centiles. (ii) There were relatively large inter-laboratory cut-off variations even within the same platform and the variability was marginally attenuated when results were expressed as ratios (test-to-normal pooled plasma). The take-home message is that cut-off values should be determined locally. (iii) There were differences between cut-off values calculated as 99th or 95th centiles that translate into a different LA detection rate (the lower the centile the greater the detection rate). The take-home message is that cut-off values determined as the 95th centile allow a better LA detection rate.

Fibrin structure in organized thrombotic material removed during pulmonary artery endarterectormy: the effect of vessel calibre

Pulmonary endarterectomy (PEA) is a curative therapeutic approach in patients with chronic thromboembolic pulmonary hypertension (CTEPH). The location-dependent structural differences of thrombotic material found in pulmonary arteries in CTEPH are poorly investigated. We present the case of a 47-year-old woman with antiphospholipid syndrome, diabetes mellitus and abnormal fibrin phenotype, who underwent PEA for CTEPH. Intravascular material removed bilaterally during PEA (from lobar, segmental and sub-segmental arteries) has been studied using light and scanning electron microscopy (SEM). Light microscopy showed tighter fibrous network in the portions of intraluminal thrombotic material facing the vessel wall, which contained collagen and fibrin fibers, and abundant cells. Cells, evaluated by immunostaining, were present in the whole removed material. Tissue factor expression was also observed with the highest values in the portions of intravascular material facing the vessel wall. In the main pulmonary arteries, SEM images revealed thick fibers of fibrous proteins loosly meshed and few erythrocytes and platelets between them (both dysmorphic "wedged" and fresh cells were present). In the fibrotic layers, containing mainly collagen and fibrin, removed from the lobar/segmental pulmonary arteries we found a stepwise increase in fiber density with decreasing vessel calibre, followed by denser fibrous networks composed of thinner fibers. Elastic fibers in the lobar and segmental arteries were aligned along the blood flow vector. These findings demonstrate differences in the structure of endarterectomized PEA material dependent on the vessel calibre and might contribute to understanding of CTEPH pathophysiology.

Potential influences of complement factor H in autoimmune inflammatory and thrombotic disorders

Complement system homeostasis is important for host self-protection and anti-microbial immune surveillance, and recent research indicates roles in tissue development and remodelling. Complement also appears to have several points of interaction with the blood coagulation system. Deficiency and altered function due to gene mutations and polymorphisms in complement effectors and regulators, including Factor H, have been associated with familial and sporadic autoimmune inflammatory - thrombotic disorders, in which autoantibodies play a part. These include systemic lupus erythematosus, rheumatoid arthritis, atypical haemolytic uremic syndrome, anti-phospholipid syndrome and age-related macular degeneration. Such diseases are generally complex - multigenic and heterogeneous in their symptoms and predisposition/susceptibility. They usually need to be triggered by vascular trauma, drugs or infection and non-complement genetic factors also play a part. Underlying events seem to include decline in peripheral regulatory T cells, dendritic cell, and B cell tolerance, associated with alterations in lymphoid organ microenvironment. Factor H is an abundant protein, synthesised in many cell types, and its reported binding to many different ligands, even if not of high affinity, may influence a large number of molecular interactions, together with the accepted role of Factor H within the complement system. Factor H is involved in mesenchymal stem cell mediated tolerance and also contributes to self-tolerance by augmenting iC3b production and opsonisation of apoptotic cells for their silent dendritic cell engulfment via complement receptor CR3, which mediates anti-inflammatory-tolerogenic effects in the apoptotic cell context. There may be co-operation with other phagocytic receptors, such as complement C1q receptors, and the Tim glycoprotein family, which specifically bind phosphatidylserine expressed on the apoptotic cell surface. Factor H is able to discriminate between self and nonself surfaces for self-protection and anti-microbe defence. Factor H, particularly as an abundant platelet protein, may also modulate blood coagulation, having an anti-thrombotic role. Here, we review a number of interaction pathways in coagulation and in immunity, together with associated diseases, and indicate where Factor H may be expected to exert an influence, based on reports of the diversity of ligands for Factor H.

Lupus Anticoagulant Testing: Activated Partial Thromboplastin Time (APTT) and Silica Clotting Time (SCT)

Actvated partial thromboplastin time and its congener test Silica clotting time are used for the laboratory detection of lupus anticoagulants. Their performance consists of mixing test plasma with activators of the contact coagulation factors, phospholipids and calcium chloride, and recording the clotting time. Here we describe the principle, performance and extensive practical details of the two methods, the problems that may be encountered and how they can be identified and overcome.

Antiphospholipid Syndrome and Kidney Involvement: New Insights

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

Soluble analog of ApoER2 targeting beta2-glycoprotein I in immune complexes counteracts hypertension in lupus-prone mice with spontaneous antiphospholipid syndrome

Essentials (NZWxBXSB)F1 male mice develop antibodies beta2-glycoprotein I (β2GPI) and hypertension. A1-A1 is a soluble analogue of ApoE receptor 2 with a high affinity for β2GPI/antibody complexes. A1-A1 improved blood pressure and arterial elastance in (NZWxBXSB)F1 male mice. A1-A1 had no adverse effects on the hemodynamics of healthy mice.

SUMMARY

Background Antiphospholipid syndrome (APS) is diagnosed based on the presence of antiphospholipid antibodies and clinical thrombosis or fetal loss during pregnancy. Lupus-prone (NZWxBXSB)F1 male mice are the mouse model of spontaneous APS. They develop anti-β2GPI antibodies, microinfarcts and hypertension. ApoER2 is a receptor that contributes to anti-β2GPI-dependent thrombosis in APS by down-regulating endothelial nitric oxide synthase activation. Objectives A1-A1 is a small protein constructed from two identical ligand-binding modules from ApoER2, containing the binding site for β2GPI. We studied how treatment with A1-A1 affects the development of hypertension in (NZWxBXSB)F1 male mice. Methods We treated (NZWxBXSB)F1 male mice with A1-A1 for up to 4 weeks and examined changes in hemodynamics by left ventricular pressure-volume loop measurements. Results We observed improvements in blood pressure in the A1-A1 treated mice. A1-A1 prevented the deterioration of arterial elastance by decreasing systemic resistance and improving vessel compliance. We did not detect any adverse effects of the treatment in either male mice or in apparently healthy female (NZWxBXSB)F1 mice. Conclusions We demonstrated that A1-A1, which is a soluble analog of ApoER2 that binds pathological β2GPI/anti-β2GPI complexes, has a positive impact on hemodynamics in lupus-prone mice with spontaneous anti-β2GPI antibodies and hypertension.

β2GP1, Anti-β2GP1 Antibodies and Platelets: Key Players in the Antiphospholipid Syndrome

Anti-beta 2 glycoprotein 1 (anti-β2GP1) antibodies are commonly found in patients with autoimmune diseases such as the antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE). Their presence is highly associated with increased risk of vascular thrombosis and/or recurrent pregnancy-related complications. Although they are a subtype of anti-phospholipid (APL) antibody, anti-β2GP1 antibodies form complexes with β2GP1 before binding to different receptors associated with anionic phospholipids on structures such as platelets and endothelial cells. β2GP1 consists of five short consensus repeat termed "sushi" domains. It has three interchangeable conformations with a cryptic epitope at domain 1 within the molecule. Anti-β2GP1 antibodies against this cryptic epitope are referred to as 'type A' antibodies, and have been suggested to be more strongly associated with both vascular and obstetric complications. In contrast, 'type B' antibodies, directed against other domains of β2GP1, are more likely to be benign antibodies found in asymptomatic patients and healthy individuals. Although the interactions between anti-β2GP1 antibodies, β2GP1, and platelets have been investigated, the actual targeted metabolic pathway(s) and/or receptor(s) involved remain to be clearly elucidated. This review will discuss the current understanding of the interaction between anti-β2GP1 antibodies and β2GP1, with platelet receptors and associated signalling pathways.

Signs of impaired immunoregulation and enhanced effector T-cell responses in the primary antiphospholipid syndrome

INTRODUCTION

We investigated whether primary antiphospholipid syndrome (PAPS) is characterized by a deficiency in immunoregulatory pathways, a phenomenon recently implicated in the pathogenesis of autoimmune diseases.

METHODS

Serum levels of immunoregulatory (e.g., IL-10 and TGF-β1) and proinflammatory (e.g., IL-17A) cytokines were measured in PAPS, systemic lupus erythematosus (SLE) with secondary APS (SAPS), or without APS, and in healthy controls (n = 40 in each group). In a subgroup of PAPS patients we also compared phenotype and function (flow cytometry) of regulatory T-cells (Treg) and cytokine production by effector T-cells.

RESULTS

Our major finding was decreased levels of TGF-β1 in PAPS and SAPS as compared to SLE without APS and controls. TGF-β1 was the lowest in PAPS patients showing high levels of aPL IgG with significant negative correlation with the titer. SLE patients were characterized by lower serum levels of IL-2 and increased IL-17A, as compared to the other groups. The numbers of circulating Treg cells and their phenotype (e.g., FoxP3 isoforms) were not disturbed in PAPS. However, surface expression of latency associated peptide (binds TGF-β) in activated FoxP3 + cells and in vitro production of TGF-β1 were decreased in PAPS patients with high titers of aPL IgG. Moreover, frequencies of cytokine producing effector T-helper cells (including Th17) were significantly elevated in this group.

CONCLUSIONS

PAPS patients with high titers of aPL IgG antibodies were characterized by decreased systemic levels of TGF-β1 and its impaired production in vitro, suggesting impaired immunoregulation and enhanced adaptive autoimmune responses leading to the production of aPL antibodies.

The transcription, translation, transport-trail and autoimmunity: Guilt by association

The autoimmune connective tissue diseases (ACTD) are a group of diseases which share clinical features and genetic inheritance. They are characterized by systemic autoimmunity and autoantibody production with a striking predilection for cellular components involved in transcription, translation and cellular transport. Although multiple triggers of autoimmunity have been proposed for this group of diseases including microbial agents such as viruses and bacteria, drugs, ultraviolet light, environmental toxins, stress, hormones and heavy metals, the prominence of autoantibodies to components of the transcription, translation, cellular transport-trail (TTTT) suggests that the agent(s) triggering the autoimmune response potentially utilize the TTTT. For the ACTD, viruses and viral agents are the likely triggers of autoimmunity as a result of aberrant viral latency with the production of autoantibodies to the components of the cellular TTTT machinery through multiple mechanisms, perhaps including molecular mimicry, bystander activation and epitope spreading.

An A1-A1 mutant with improved binding and inhibition of β2GPI/antibody complexes in antiphospholipid syndrome

β2 glycoprotein I (β2GPI) is the most common antigen for autoimmune antibodies in antiphospholipid syndrome (APS). Thrombosis is a clinical feature of APS. We created a molecule (A1-A1) that consists of two identical β2GPI-binding modules from ApoE receptor 2 (ApoER2). A1-A1 binds to β2GPI/antibody complexes, preventing their association with ApoER2 and anionic phospholipids, and reducing thrombus size in the mouse model of APS. Here, we describe a mutant of A1-A1 (mA1-A1ND) with improved affinity for β2GPI. mA1-A1ND inhibits the binding of β2GPI to cardiolipin in the presence of anti-β2GPI antibodies, and inhibits the binding to phospholipids in plasma samples of APS patients, affecting the clotting time. Reduction of the clotting time demonstrates the presence of soluble β2GPI/antibody complexes in patients' plasma. These complexes either already exist in patients' plasma or form rapidly in the proximity to phospholipids. All members of the low-density lipoprotein receptor family bind β2GPI. Modeling studies of A1 in a complex with domain V of β2GPI (β2GPI-DV) revealed two possible modes of interaction of a ligand-binding module from lipoprotein receptors with β2GPI-DV. In both orientations, the ligand-binding module interferes with binding of β2GPI to anionic phospholipids; however, it interacts with two different but overlapping sets of lysine residues in β2GPI-DV, depending on the orientation.

An approach to differential diagnosis of antiphospholipid antibody syndrome and related conditions

The antiphospholipid antibody syndrome is a systemic, acquired, immune-mediated disorder characterized by episodes of venous, arterial, or microcirculation thrombosis and/or pregnancy abnormalities, associated with the persistent presence of autoantibodies, confirmed at least in two occasions 12 weeks apart, directed to molecular complexes consisting of phospholipids and proteins. Antiphospholipid antibody syndrome should always be considered as a potential diagnosis especially for young patients presenting with a history of thrombotic events, in particular when they occur without any obvious external trigger or any inherited thrombophilic mutation (even if 2006 criteria do not exclude antiphospholipid antibody syndrome in patients with other inherited or acquired prothrombotic conditions), or for women with recurrent pregnancy losses or later fetal deaths. Many other disorders are able to mimic antiphospholipid antibody syndrome, so a broad range of alternative diagnoses should be investigated and ruled out during clinical workup.

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

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

Altered fibrin clot structure/function in patients with antiphospholipid syndrome: association with thrombotic manifestation

We tested the hypothesis that plasma fibrin clot structure/function is unfavourably altered in patients with antiphospholipid syndrome (APS). Ex vivo plasma clot permeability, turbidity and susceptibility to lysis were determined in 126 consecutive patients with APS enrolled five months or more since thrombotic event vs 105 controls. Patients with both primary and secondary APS were characterised by 11% lower clot permeability (p<0.001), 4.8% shorter lag phase (p<0.001), 10% longer clot lysis time (p<0.001), and 4.7% higher maximum level of D-dimer released from clots (p=0.02) as compared to the controls. Scanning electron microscopy images confirmed denser fibrin networks composed of thinner fibres in APS. Clots from patients with "triple-antibody positivity" were formed after shorter lag phase (p=0.019) and were lysed at a slower rate (p=0.004) than in the remainder. Clots from APS patients who experienced stroke and/or myocardial infarction were 8% less permeable (p=0.01) and susceptible to lysis (10.4% longer clot lysis time [p=0.006] and 4.5% slower release of D-dimer from clots [p=0.01]) compared with those following venous thromboembolism alone. Multivariate analysis adjusted for potential confounders showed that in APS patients, lupus anticoagulant and "triple-positivity" were the independent predictors of clot permeability, while "triple-positivity" predicted lysis time. We conclude that APS is associated with prothrombotic plasma fibrin clot phenotype, with more pronounced abnormalities in arterial thrombosis. Molecular background for this novel prothrombotic mechanism in APS remains to be established.

Inhibition of thrombotic properties of persistent autoimmune anti-β2GPI antibodies in the mouse model of antiphospholipid syndrome

Antiphospholipid syndrome (APS) is an autoimmune disorder with increased risk for thrombosis and pregnancy losses. β2-glycoprotein I (β2GPI) is the major antigen for clinically relevant antibodies in APS. We engineered a molecule, A1-A1, which interferes with 2 prothrombotic mechanisms in APS: the binding of β2GPI to negatively charged cellular surfaces and ApoE receptor 2. We studied how A1-A1 affects arterial thrombosis in vivo in lupus-prone (NZW × BXSB)F1 male mice. For the first time, we demonstrated that A1-A1 efficiently reduces thrombus size in vivo in the presence of chronic autoimmune anti-β2GPI antibodies. We have shown that A1-A1 interferes with thrombotic properties of β2GPI/antibody complexes and does not affect normal thrombus formation in the absence of anti-β2GPI antibodies. A1-A1 inhibits prothrombotic properties of β2GPI/antibody complexes in wild-type mice after acute infusion with anti-β2GPI antibodies, as well as in mice expressing persistent autoimmune anti-β2GPI antibodies. A1-A1 reduced thrombus size in a mouse model of APS in the presence of lupus features, suggesting that A1-A1 might effectively interfere with thrombosis not only in primary APS but also in APS secondary to lupus. Our results suggest that A1-A1 could be a prototype for an antithrombotic drug in APS.

Serum anticardiolipin concentrations in patients with chronic periodontitis following scaling and root planing

BACKGROUND

Anticardiolipin antibodies (antiCl), present in some patients with autoimmune disease, are associated with thrombosis, fetal loss, and other conditions. A significant proportion of patients with chronic periodontitis (CP) test positive for antiCl, likely because some periodontal pathogens contain antigens homologous to the target antigen of antiCl on the serum protein β-2 glycoprotein-I (β2GPI) and thus can induce antiCl by molecular mimicry. The authors hypothesized that treatment of periodontitis by scaling and root planing (SRP) could therefore decrease serum titers of antiCl in patients with CP.

METHODS

Thirty patients with CP received complete periodontal examinations at baseline including assessment of probing depth, attachment loss, gingival index, and plaque index. SRP was performed in two sessions at 2-week intervals. Eight weeks later, patients were reexamined. Blood samples were taken at baseline, 2 weeks after the initial therapy appointment, and 8 weeks after the completion of treatment for assessment of immunoglobulin (Ig)G and IgM antiCl levels.

RESULTS

All periodontal parameters improved significantly. Consistent with previous observations, five (16.7%) of the 30 patients exhibited elevated levels of IgG or IgM antiCl at baseline. Following treatment, the concentrations of IgG and IgM antiCl remained unchanged for the entire cohort of 30 patients. However, in the five patients with elevated antiCl at baseline, IgM antiCl concentrations decreased significantly (P = 0.0008) owing to therapy, while IgG antiCl did not.

CONCLUSION

The oral microflora is a likely source of antigen inducing antiCl in CP, since IgM antiCl levels can be reduced in the short term with conservative therapy.

Anticardiolipin in porphyromonas gingivalis antisera causes fetal loss in mice

β2-glycoprotein I (β2GPI)-dependent anticardiolipin autoantibodies (aCl) are associated with thrombosis and fetal loss. Some microbial pathogens can induce pathogenic antibodies cross-reactive with β2GPI. Sera from a significant percentage of periodontitis patients contain aCl, and some periodontal pathogens contain antigens with peptide sequences having homology to β2GPI. We hypothesized that antibodies raised against P. gingivalis (aPg) contain pathogenic aCl that induce fetal resorption. We immunized mice with β2GPI, P. gingivalis W83, or an arg-gingipain-defective mutant of P. gingivalis (HF18). IgG fractions of aPg were immunoabsorbed to remove aCl-like antibodies (abs-aPg). IgG fractions were administered intravenously into tail veins of mated BALB/c females at day 0 of pregnancy. At day 15, the proportions of fetal resorptions were evaluated. The prevalence of fetal loss was significantly greater in the aPg group than in the control IgG group (21.2% vs. 5.3%, p = .001), and greater in the aPg group than in the abs-aPg group (21.2% vs. 12%, p < .05). There were no fetal resorptions observed in the aPgHF18 group (p = .0005 compared with aPg, p = .17 compared with control). aPg antibody contains activity consistent with pathogenic aCl, and the antigen inducing the antibodies that cause increased fetal loss may be on the arg-gingipain protease of P. gingivalis.

Identification of the binding site for fondaparinux on Beta2-glycoprotein I

Antiphospholipid syndrome (APS) is an autoimmune disease with clinical manifestations of thrombosis and pregnancy complications. Beta2-glycoprotein I (β2GPI) is the major antigen for the APS-related antibodies. Heparin, low-molecular weight heparin and the synthetic pentasaccharide fondaparinux are commonly used for prophylaxis and treatment of thrombosis in patients with antiphospholipid syndrome. These antithrombotic drugs bind and activate antithrombin III to inactivate blood clotting proteases. Heparin and heparin derivatives might have a direct beneficial effect in APS via binding to β2GPI and interfering with prothrombotic properties of β2GPI/antibody complexes. We compared fondaparinux to heparin regarding its ability to bind β2GPI and inhibit the binding of β2GPI/antibody complexes to negatively charged phospholipids and endothelial cells. Although heparin and fondaparinux bind β2GPI at therapeutically relevant doses, neither fondaparinux nor heparin was efficient in inhibition of the binding of β2GPI/antibody complexes to negatively charged phospholipids and endothelial cells. Our studies suggest that these drugs do not act on pathological properties of β2GPI/antibody complexes, emphasizing the need for a new treatment specific for β2GPI-related thrombosis in APS. We observed that the binding interface of fondaparinux on β2GPI does not include the lysine residues known to be critical for binding of heparin. The docking model of the β2GPI complex with fondaparinux is in agreement with multiple experimental observations.