Vimentin/cardiolipin complex as a new antigenic target of the antiphospholipid syndrome

Non-criteria and criteria antiphospholipid antibodies and their association with pregnancy outcomes in women with a history of miscarriage: A retrospective study

INTRODUCTION

The objective of this study was to investigate both antiphospholipid antibodies (aPLs) and non-criteria aPLs (NC-aPLs) in relation with pregnancy outcomes.

METHODS

We retrospectively analyzed 1574 pregnant women with experienced at least one miscarriage who were tested for aPLs and NC-aPLs, and compared their clinical characteristics, immune biomarkers, and pregnancy outcomes. The χ2 test or Fisher's exact test compared pregnancy outcomes among patients negative for all aPLs, positive for NC‑aPLs subtypes, and positive for criteria aPLs subtypes.

RESULTS

Multivariate logistic regression analysis indicated that positive aPLs (OR = 2.216, 95 % CI 1.381-3.558), and positive NC-aPLs (OR = 1.619, 95 % CI 1.245-2.106) are linked to adverse outcomes. For fetal loss, positive aPLs (OR = 2.354, 95 % CI 1.448-3.829), NC-aPLs (OR = 1.443, 95 % CI 1.076-1.936) were significant. Premature delivery was associated with positive NC-aPLs (OR = 2.102, 95 % CI 1.452-3.043). In the NC-aPLs positive group, the rate of adverse outcomes was higher in the multiple-positive subgroup (77.8 %) compared to the double-positive (52.3 %) and single-positive (37.0 %) subgroups. The rates of fetal loss and premature delivery were also higher in the multiple-positive NC-aPLs subgroup compared to the single-positive subgroup (48.1 % vs. 22.6 % for fetal loss and 57.1 % vs. 16.5 % for premature delivery).

DISCUSSION

Our findings suggest that both aPLs and NC-aPLs are associated with an increased incidence of adverse pregnancy outcomes, and patients presenting with multiple NC-aPLs positivity were found to have a higher incidence of adverse outcomes compared to their single-positive counterparts.

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.

Complement biomarkers in the antiphospholipid syndrome - Approaches to quantification and implications for clinical management

Complement is a major driver of antiphospholipid syndrome (APS) and a promising therapeutic target in refractory and catastrophic APS. Complement testing in APS is largely limited to research settings, and reliable, rapid-turnaround biomarkers are needed to predict those at risk for adverse clinical outcomes and most likely to benefit from complement inhibition. We review complement biomarkers and their association with thrombosis and obstetric outcomes, including: (i) complement proteins and activation fragments in the fluid phase; (ii) assays that evaluate complement on cell membranes (e.g. in vivo cell-bound complement fragments, hemolytic assays, and ex vivo 'functional' cell-based assays, and (iii) sequencing of complement genes. Current studies highlight the inconsistencies in testing both between studies and various aPL/APS subgroups, suggesting that either cell-based testing or multiplex panels employing a combination of biomarkers simultaneously may be most clinically relevant. Standardization of complement assays is needed to ensure reproducibility and establish clinically relevant applications.

Activation of Platelet mTORC2/Akt Pathway by Anti-β2GP1 Antibody Promotes Thrombosis in Antiphospholipid Syndrome

BACKGROUND

Anti-β2GP1 (β2-glycoprotein 1) antibodies are the primary pathogenic antibody to promote thrombosis in antiphospholipid syndrome (APS), yet the underlying mechanism remains obscure. We aimed to explore the intracellular pathway that mediated platelet activation.

METHODS

Platelets were isolated from patients with APS and subjected to RNA sequencing. Platelet aggregation, the release of platelet granules, platelet spreading, and clot retraction were detected to evaluate platelet activation. We purified anti-β2GP1 antibodies from patients with APS and the total IgG from healthy donors to stimulate platelets with/without FcγRIIA (Fcγ receptor IIA) blocking antibody or Akt (protein kinase B) inhibitor. Platelet-specific Sin1 (stress-activated protein kinase-interacting protein) deficiency mice were established. The thrombus model of inferior vena cava flow restriction, ferric chloride-induced carotid injury model, and laser-induced vessel wall injury in cremaster arterioles model were constructed after administration of anti-β2GP1 antibodies.

RESULTS

Combined RNA sequencing and bioinformatics analysis suggested that APS platelets exhibited increased levels of mRNA associated with platelet activation, which was in line with the hyperactivation of APS platelets in response to stimuli. Platelet activation in APS platelets was accompanied by upregulation of the mTORC2 (mammalian target of the rapamycin complex 2)/Akt pathway and increased levels of SIN1 phosphorylation at threonine 86. Anti-β2GP1 antibody derived from patients with APS enhanced platelet activation and upregulated the mTORC2/Akt pathway. Moreover, the Akt inhibitor weakened the potentiating effect of the anti-β2GP1 antibody on platelet activation. Notably, Sin1 deficiency suppresses anti-β2GP1 antibody-enhanced platelet activation in vitro and thrombosis in all 3 models.

CONCLUSIONS

This study elucidated the novel mechanism involving the mTORC2/Akt pathway, which mediates the promotion of platelet activation and induction of thrombosis by the anti-β2GP1 antibody. The findings suggest that SIN1 may be a promising therapeutic target for the treatment of APS.

Trophoblast Cell Function in the Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is a complex thrombo-inflammatory autoimmune disease characterized by the presence of antiphospholipid antibodies (aPL). Women with APS are at high risk of recurrent early pregnancy loss as well as late obstetrical complications-premature birth due to placental insufficiency or severe preeclampsia. Accumulating evidence implies that vascular thrombosis is not the only pathogenic mechanism in obstetric APS, and that the direct negative effect of aPL on the placental cells, trophoblast, plays a major role. In this review, we summarize the current findings regarding the potential mechanisms involved in aPL-induced trophoblast dysfunction. Introduction on the APS and aPL is followed by an overview of the effects of aPL on trophoblast-survival, cell function and aPL internalization. Finally, the implication of several non-coding RNAs in pathogenesis of obstetric APS is discussed, with special emphasis of their possible role in trophoblast dysfunction and the associated mechanisms.

Modulation of the activation of endothelial nitric oxide synthase and nitrosative stress biomarkers by aspirin triggered lipoxins: A possible mechanism of action of aspirin in the antiphospholipid syndrome

PROBLEM

Antiphospholipid syndrome (APS) is characterized by the clinical manifestation of vascular thrombosis (VT) or pregnancy morbidity (PM) and antiphospholipid antibodies (aPL) that can modify the nitric oxide production. Low-dose aspirin is used in the prevention and treatment of diverse alterations of pregnancy. One of the mechanisms of action of aspirin is to induce the production of aspirin-triggered-lipoxins (ATL). The aim of this study was to evaluate the modulatory effect of ATL over the activation of endothelial nitric oxide synthase (eNOS) and nitrosative stress biomarkers induced by aPL.

METHODS

We used polyclonal IgG and sera from women with aPL and PM/VT or VT only, and from women with PM only and positive for non-criteria aPL (SN-OAPS). In these sera, biomarkers of nitrosative stress (nitrites and nitrotyrosine) were measured. The protein expression of nitrotyrosine and the phosphorylation of eNOS (at Ser1177) were estimated in human umbilical vein endothelial cells (HUVECs) stimulated with polyclonal IgG with or without ATL.

RESULTS

Women with SN-OAPS showed increased circulating levels of nitrites and nitrotyrosine. Likewise, polyclonal IgG from either SN-OAPS or VT patients stimulated nitrotyrosine expression in HUVECs. ATL decreased the nitrotyrosine expression induced by polyclonal IgG from the SN-OAPS group. ATL also recovered the reduced eNOS phosphorylation at Ser1177 in HUVECs stimulated with polyclonal IgG from women with PM/VT or SN-OAPS.

CONCLUSIONS

Increased nitrosative stress present in serum of women with SN-OAPS is associated with IgG-mediated impaired endothelial NO synthesis in endothelial cells. ATL prevent these cellular changes.

High-throughput sequencing technology facilitates the discovery of novel biomarkers for antiphospholipid syndrome

Antiphospholipid syndrome (APS) is characterized by arterial and venous thrombosis and/or morbid pregnancy, accompanied by persistent antiphospholipid antibody (aPL) positivity. However, due to the complex pathogenesis of APS and the large individual differences in the expression of aPL profiles of patients, the problem of APS diagnosis, prognosis judgment, and risk assessment may not be solved only from the antibody level. It is necessary to use new technologies and multiple dimensions to explore novel APS biomarkers. The application of next-generation sequencing (NGS) technology in diseases with a high incidence of somatic mutations, such as genetic diseases and tumors, has been very mature. Thus, we try to know the research and application progress of APS by NGS technology from genome, transcriptome, epigenome and other aspects. This review will describe the related research of NGS technology in APS and provide more reference for the deep understanding of APS-related screening markers and disease pathogenesis.

Determination of Thrombogenicity Levels of Various Antiphospholipid Antibodies by a Modified Thrombin Generation Assay in Patients with Suspected Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is a hypercoagulable state accompanied by the presence of heterogeneous antiphospholipid antibodies (aPL), which nonspecifically affect hemostasis by the presence of lupus anticoagulans (LA), anticardiolipin antibodies (aCL), antibodies against β2-glycoprotein-I (anti-β2GPI), but also non-criteria antibodies such as antibodies against β2-glycoprotein-I domain I (anti-DI), anti-phosphatidylserine/prothrombin (anti-PS/PT), anti-annexin V, and many others. The main target of the antibodies is the activated protein C (APC) system, the elimination of which can manifest itself as a thrombotic complication. The aim of this study was to determine the thrombogenicity of antibodies using a modified protein C-activated thrombin generation assay (TGA) on a group of 175 samples suspected of APS. TGA was measured with/without APC and the ratio of both measurements was evaluated (as for APC resistance), where a cut-off was calculated ≤4.5 (90th percentile) using 21 patients with heterozygous factor V Leiden mutation (FV Leiden heterozygous). Our study demonstrates the well-known fact that multiple positivity of different aPLs is a more severe risk for thrombosis than single positivity. Of the single antibody positivity, LA antibodies are the most serious (p value < 0.01), followed by aCL and their subgroup anti-DI (p value < 0.05). Non-criteria antibodies anti-annexin V and anti-PT/PS has a similar frequency occurrence of thrombogenicity as LA antibodies but without statistical significance or anti-β2GPI1 positivity. The modified TGA test can help us identify patients in all groups who are also at risk for recurrent thrombotic and pregnancy complications; thus, long-term prophylactic treatment is appropriate. For this reason, it is proving increasingly beneficial to include the determination antibodies in combination with modified TGA test.

Pathogenesis, Diagnosis and Management of Obstetric Antiphospholipid Syndrome: A Comprehensive Review

Antiphospholipid syndrome is an autoimmune disorder characterized by vascular thrombosis and/or pregnancy morbidity associated with persistent antiphospholipid antibody positivity. Cases fulfilling the Sydney criteria for obstetric morbidity with no previous thrombosis are known as obstetric antiphospholipid syndrome (OAPS). OAPS is the most identified cause of recurrent pregnancy loss and late-pregnancy morbidity related to placental injury. Cases with incomplete clinical or laboratory data are classified as obstetric morbidity APS (OMAPS) and non-criteria OAPS (NC-OAPS), respectively. Inflammatory and thrombotic mechanisms are involved in the pathophysiology of OAPS. Trophoblasts, endothelium, platelets and innate immune cells are key cellular players. Complement activation plays a crucial pathogenic role. Secondary placental thrombosis appears by clot formation in response to tissue factor activation. New risk assessment tools could improve the prediction of obstetric complication recurrences or thromboses. The standard-of-care treatment consists of low-dose aspirin and prophylactic low molecular weight heparin. In refractory cases, the addition of hydroxychloroquine, low-dose prednisone or IVIG improve pregnancy outcomes. Statins and eculizumab are currently being tested for treating selected OAPS women. Finally, we revisited recent insights and concerns about the pathophysiology, diagnosis and management of OAPS.

The Pathophysiology of The Antiphospholipid Syndrome: A Perspective From The Blood Coagulation System

The antiphospholipid syndrome (APS), a systemic autoimmune disease characterized by a hypercoagulability associated to vascular thrombosis and/or obstetric morbidity, is caused by the presence of antiphospholipid antibodies such as lupus anticoagulant, anti-β-2-glycoprotein 1, and/or anticardiolipin antibodies. In the obstetrical APS, antiphospholipid antibodies induce the production of proinflammatory cytokines and tissue factor by placental tissues and recruited neutrophils. Moreover, antiphospholipid antibodies activate the complement system which, in turn, induces a positive feedback leading to recruitment of neutrophils as well as activation of the placenta. Activation of these cells triggers myometrial contractions and cervical ripening provoking the induction of labor. In thrombotic and obstetrical APS, antiphospholipid antibodies activate endothelial cells, platelets, and neutrophils and they may alter the multimeric pattern and concentration of von Willebrand factor, increase the concentration of thrombospondin 1, reduce the inactivation of factor XI by antithrombin, increase the activation of factor XII, and reduce the activity of tissue plasminogen activator with the subsequent production of plasmin. All these effects result in less permeable clots, denser, thinner, and with more branched fibrin fibers which are more difficult to lysate. As a consequence, thrombosis, the defining clinical criterion of APS, complicates the clinical course of the patient.

Pathophysiology of the Antiphospholipid Antibody Syndrome

The antiphospholipid syndrome is characterized by antibodies directed against phospholipid-binding proteins and phospholipids attached to cell membrane receptors, mitochondria, oxidized lipoproteins, and activated complement components. When antibodies bind to these complex antigens, cells are activated and the coagulation and complement cascades are triggered, culminating in thrombotic events and pregnancy morbidity that further define the syndrome. The phospholipid-binding proteins most often involved are annexins II and V, β2-glycoprotein I, prothrombin, and cardiolipin. A distinguishing feature of the antiphospholipid syndrome is the "lupus anticoagulant". This is not a single entity but rather a family of antibodies directed against complex antigens consisting of β2-glycoprotein I and/or prothrombin bound to an anionic phospholipid. Although these antibodies prolong in vitro clotting times by competing with clotting factors for phospholipid binding sites, they are not associated with clinical bleeding. Rather, they are thrombogenic because they augment thrombin production in vivo by concentrating prothrombin on phospholipid surfaces. Other antiphospholipid antibodies decrease the clot-inhibitory properties of the endothelium and enhance platelet adherence and aggregation. Some are atherogenic because they increase lipid peroxidation by reducing paraoxonase activity, and others impair fetal nutrition by diminishing placental antithrombotic and fibrinolytic activity. This plethora of destructive autoantibodies is currently managed with immunomodulatory agents, but new approaches to treatment might include vaccines against specific autoantigens, blocking the antibodies generated by exposure to cytoplasmic DNA, and selective targeting of aberrant B-cells to reduce or eliminate autoantibody production.

Proteomics and enriched biological processes in Antiphospholipid syndrome: A systematic review

Identification of differentially expressed proteins in antiphospholipid syndrome (APS) is a developing area of research for unique profiles of this pathology. Advances in technologies of mass spectrometry brings improvements in proteomics and results in assessment of soluble or cellular proteins which could be candidates for clinical biomarkers of primary APS. The use of blood as a source of proteins ease the acquisition of samples for proteomics analyses and later for disease diagnosis. We performed a systematic review to explore the proteomics studies carried out in circulating released proteins (serum, plasma) or cellular proteins (monocytes and platelets) of APS patients. The study groups differentiate among clinical APS cases with the aim to translate molecular findings to disease stratification and to improve APS diagnosis and prognosis. These studies also include the unravelling of new autoantibodies in non-criteria APS or how post-translational protein modifications provides clues about the pathological mechanisms of antigen-autoantibody recognition. Herein, we identified 82 proteins that were dysregulated in APS across eleven studies. Enrichment analysis revealed its connection to cellular activation and degranulation that eventually leads to thrombosis as the main biological process highlighted by these studies. Validation of APS-relevant proteins by functional and mechanistic studies will be essential for patient stratification and the development of targeted therapies for every clinical subtype of APS.

Effect of heparanase inhibitor on tissue factor overexpression in platelets and endothelial cells induced by anti-β2-GPI antibodies

BACKGROUND

Anti-phospholipid syndrome (APS) is characterized by arterial and/or venous thrombosis and pregnancy morbidity associated with the presence of "anti-phospholipid antibodies." Thrombosis may be the result of a hypercoagulable state related to activation of endothelial cells and platelets by anti-β2-glycoprotein I (β2-GPI) antibodies. Anti-β2-GPI antibodies induce a proinflammatory and procoagulant phenotype in these cells that, after activation, express tissue factor (TF), the major initiator of the clotting cascade, playing a role in thrombotic manifestations. Moreover, TF expression may also be induced by heparanase, an endo-β-D-glucuronidase, that generates heparan sulfate fragments, regulating inflammatory responses.

OBJECTIVES

In this study we analyzed, in human platelets and endothelial cells, the effect of a new symmetrical 2-aminophenyl-benzazolyl-5-acetate derivative (RDS3337), able to inhibit heparanase activity, on signal transduction pathways leading to TF expression triggered by anti-β2-GPI.

METHODS

Platelets and endothelial cells were incubated with affinity purified anti-β2-GPI after pretreatment with RDS3337. Cell lysates were analyzed for phospho-interleukin-1 receptor-associated kinase 1 (IRAK1), phospho-p65 nuclear factor kappa B (NF-κB) and TF by western blot. In addition, platelet activation and secretion by ATP release dosage were evaluated.

RESULTS

IRAK phosphorylation and consequent NF-κB activation, as well as TF expression triggered by anti-β2-GPI treatment were significantly prevented by previous pretreatment with RDS3337. In the same vein, pretreatment with RDS3337 prevented platelet aggregation and ATP release triggered by anti-β2-GPI antibodies.

CONCLUSION

These findings support the view of heparanase involvement in a prothrombotic state related to APS syndrome, suggesting a novel target to regulate overexpression of procoagulant protein(s).

Anti-vimentin/cardiolipin IgA in the anti-phospholipid syndrome: A new tool for 'seronegative' diagnosis

Anti-phospholipid syndrome (APS) is a systemic autoimmune disorder defined by the simultaneous presence of vascular clinical events, pregnancy morbidity and anti-phospholipid antibodies (aPL). In clinical practice, it is possible to find patients with APS who are persistently negative for the routine aPL tests (seronegative APS; SN-APS). Recently, the identification of aPL immunoglobulin (Ig)A and/or anti-β2-glycoprotein-I (β2-GPI) IgA was shown to represent a further test in SN-APS patients. In this study we analyzed the presence of anti-vimentin/cardiolipin (aVim/CL) IgA in a large cohort of patients with SN-APS, evaluating their possible association with clinical manifestations of the syndrome. This study includes 60 consecutive SN-APS patients, 30 patients with APS and 40 healthy donors. aVim/CL IgA were detected by enzyme-linked immunosorbent assay (ELISA). Results show that 12 of 30 APS patients (40%) and 16 of 60 SN-APS patients (26.7%) resulted positive for aVim/CL IgA. Interestingly, SN-APS patients who tested positive for aVim/CL IgA showed a higher prevalence of arterial thrombosis (p = 0.017, likelihood positive ratio = 5.7). This study demonstrates for the first time, to our knowledge, the presence of aVim/CL IgA in sera of patients with APS. In particular, they revealed a potential usefulness in identification of a significant proportion of SN-APS patients. Moreover, as patients tested positive for aVim/CL IgA reported a high likelihood ratio to have the clinical features of APS, this test may be considered a suitable approach in the clinical evaluation of SN-APS.

"Non-criteria antiphospholipid antibodies": bridging the gap between seropositive and seronegative Antiphospholipid Syndrome

OBJECTIVE

We aimed to analyze the prevalence of non-criteria anti-phospholipid (aPL) antibodies and their role in the diagnosis, treatment and prognosis in a cohort of patients with clinical features consistent with a diagnosis of antiphospholipid syndrome (APS), but persistently negative for criteria aPL-anti-cardiolipin antibodies (aCL), anti-β2-glycoprotein I antibodies (aβ2-GPI), and lupus anticoagulant (LA) - named seronegative APS (SN-APS).

METHODS

Sera from SN-APS patients were tested for aCL by TLC-immunostaining, anti-vimentin/cardiolipin (aVim/CL) and anti-phosphatidylserine/prothrombin (anti-PS/PT) by ELISA. Control groups of our study were APS patients and healthy controls.

RESULTS

We enrolled 114 consecutive SN-APS patients, 69 (60.5%) resulted positive for at least one non-criteria test in two occasions 12 weeks apart. Among the persistently positive patients to these tests, 97% resulted positive for aCL by TLC-immunostaining, 52.3% for aVim/CL and 17.4% for aPS/PT. SN-APS patients with double positivity (aCL by TLC-immunostaining and aVim/CL) showed a likelihood positive ratio of 8 to present mixed thrombotic and obstetrical features. Among SN-APS patients tested positive, after the therapeutic changes, 3 cases of recurrent thrombosis were observed [median follow-up 41 months (IQR 39.5)]. Twenty pregnancies were recorded in 17 SN-APS patients after the detection of unconventional aPL and 12 of them (60%) experienced a good outcome under conventional treatment for APS.

CONCLUSIONS

This is the largest monocentric study demonstrating that aCL tested by TLC-immunostaining and aVim/CL can detect aPL positivity in SN-APS. It may encourage clinicians to monitoring and providing adequate targeted therapy, which improve SN-APS prognosis.

Antiphospholipid syndrome: the need for new international classification criteria

Introduction: As soon as the association of lupus anticoagulant (LAC) and anticardiolipin antibodies (aCL) with thrombosis and miscarriages was described in the 1980s, the definition of the antiphospholipid syndrome (APS) became a need. Early descriptions of the disease by members of the Graham Hughes team included broad categories and unexplained laboratory inclusions. Over time, new clinical and experimental data refined the criteria, especially the obstetric manifestations, as well as the laboratory criteria.Areas covered: The authors performed a review of the literature using the PubMed database, and the following keywords were used: 'antiphospholipid antibody', 'antiphospholipid syndrome', and 'criteria of antiphospholipid'. The history of antiphospholipid criteria, clinical and experimental advancements, and other expert opinions were included in this paper.Expert opinion: It has been 14 years since an international congress on antiphospholipid antibodies has generated new classification based on the recent extensive research performed in the field. Currently, there is a need to update the international APS classification taking into consideration the inclusion of new clinical criteria such as aPL-related nephropathy as well as new standardized antibody specificities (e.g., anti-phosphatidylserine/prothrombin antibodies) with the adoption of a standardized scoring system that can stratify APS patients.

Current Promising Biomarkers and Methods in the Diagnostics of Antiphospholipid Syndrome: A Review

Antiphospholipid syndrome (APS) is a hypercoagulation condition associated with the incidence of heterogenic antiphospholipid antibodies (aPLs), which non-specifically affect hemostasis processes. APS is clinically manifested by recurrent arterial and venous thromboses and reproduction losses. The aPL antibodies, which may induce clinical manifestations of APS, include criteria antibodies anti-cardiolipin, anti-β2-glycoprotein-I, and lupus anticoagulant, but also non-criteria antibodies, for example anti-β2-glycoprotein-I domain I, anti-phosphatidylserine/prothrombin, anti-annexin V, and many others. APS occurs mostly in patients of younger and middle age, most frequently in females. Laboratory diagnostics of APS are quite difficult, as they include a wide spectrum of examining methods, which are based on various principles of detection and are performed using various laboratory techniques. The objective of the review is to describe the current state of potentially examined biomarkers and methods in APS diagnostics. The aforementioned biomarkers are lupus anticoagulant, anti-β2-glycoprotein-I, anti-cardiolipin, anti-β2-glycoprotein-I domain I, anti-phosphatidylserine/prothrombin, anti-β2-glycoprotein-I IgA, anti-cardiolipin IgA, anti-annexin V and II, anti-prothrombin, anti-cardiolipin/vimentin, anti-protein S/protein C, and antibodies against phospholipid antigens for whose diagnostics we may use some of the methods established for a long time and some of the modern methods—the coagulation method for the determination of lupus anticoagulant (LA), enzyme-linked imunosorbent assay (ELISA), chemiluminescence analysis (CLIA), multiplex fluorescence flow immunoassay (MFFIA), fluorescence enzyme immunoassay (EliA), line immunoassay (LIA), multiline dot assay (MLDA), and thin-layer chromatography (TLC). Conclusion: Antibodies against phosphatidylethanolamine, phosphatidic acid, phosphatidylserine, phosphatidylinositol, cardiolipin/vimentin complex, and annexin V are currently the most studied new markers. However, these assays have not been standardized until now, both from the laboratory and clinical point of view. In this review we summarize the evidence of the most studied aPL markers and their potential clinical significance in seronegative APS (SN-APS).

Molecular Mechanisms of "Antiphospholipid Antibodies" and Their Paradoxical Role in the Pathogenesis of "Seronegative APS"

Antiphospholipid Syndrome (APS) is an autoimmune disease characterized by arterial and/or venous thrombosis and/or pregnancy morbidity, associated with circulating antiphospholipid antibodies (aPL). In some cases, patients with a clinical profile indicative of APS (thrombosis, recurrent miscarriages or fetal loss), who are persistently negative for conventional laboratory diagnostic criteria, are classified as "seronegative" APS patients (SN-APS). Several findings suggest that aPL, which target phospholipids and/or phospholipid binding proteins, mainly β-glycoprotein I (β-GPI), may contribute to thrombotic diathesis by interfering with hemostasis. Despite the strong association between aPL and thrombosis, the exact pathogenic mechanisms underlying thrombotic events and pregnancy morbidity in APS have not yet been fully elucidated and multiple mechanisms may be involved. Furthermore, in many SN-APS patients, it is possible to demonstrate the presence of unconventional aPL ("non-criteria" aPL) or to detect aPL with alternative laboratory methods. These findings allowed the scientists to study the pathogenic mechanism of SN-APS. This review is focused on the evidence showing that these antibodies may play a functional role in the signal transduction pathway(s) leading to thrombosis and pregnancy morbidity in SN-APS. A better comprehension of the molecular mechanisms triggered by aPL may drive development of potential therapeutic strategies in APS patients.

Vimentin as a Multifaceted Player and Potential Therapeutic Target in Viral Infections

Vimentin is an intermediate filament protein that plays key roles in integration of cytoskeletal functions, and therefore in basic cellular processes such as cell division and migration. Consequently, vimentin has complex implications in pathophysiology. Vimentin is required for a proper immune response, but it can also act as an autoantigen in autoimmune diseases or as a damage signal. Although vimentin is a predominantly cytoplasmic protein, it can also appear at extracellular locations, either in a secreted form or at the surface of numerous cell types, often in relation to cell activation, inflammation, injury or senescence. Cell surface targeting of vimentin appears to associate with the occurrence of certain posttranslational modifications, such as phosphorylation and/or oxidative damage. At the cell surface, vimentin can act as a receptor for bacterial and viral pathogens. Indeed, vimentin has been shown to play important roles in virus attachment and entry of severe acute respiratory syndrome-related coronavirus (SARS-CoV), dengue and encephalitis viruses, among others. Moreover, the presence of vimentin in specific virus-targeted cells and its induction by proinflammatory cytokines and tissue damage contribute to its implication in viral infection. Here, we recapitulate some of the pathophysiological implications of vimentin, including the involvement of cell surface vimentin in interaction with pathogens, with a special focus on its role as a cellular receptor or co-receptor for viruses. In addition, we provide a perspective on approaches to target vimentin, including antibodies or chemical agents that could modulate these interactions to potentially interfere with viral pathogenesis, which could be useful when multi-target antiviral strategies are needed.

Recommendations of the Spanish Rheumatology Society for Primary Antiphospholipid Syndrome. Part I: Diagnosis, Evaluation and Treatment

OBJECTIVE

The difficulty in diagnosis and the spectrum of clinical manifestations that can determine the choice of treatment for primary antiphospholipid syndrome (APS) has fostered the development of recommendations by the Spanish Society of Rheumatology (SER), based on the best possible evidence. These recommendations can serve as a reference for rheumatologists and other specialists involved in the management of APS.

METHODS

A panel of four rheumatologists, a gynaecologist and a haematologist with expertise in APS was created, previously selected by the SER through an open call or based on professional merits. The stages of the work were: identification of the key areas for drafting the document, analysis and synthesis of the scientific evidence (using the Scottish Intercollegiate Guidelines Network [SIGN] levels of evidence) and formulation of recommendations based on this evidence and formal assessment or reasoned judgement techniques (consensus techniques).

RESULTS

46 recommendations were drawn up, addressing five main areas: diagnosis and evaluation, measurement of primary thromboprophylaxis, treatment for APS or secondary thromboprophylaxis, treatment for obstetric APS and special situations. These recommendations also include the role of novel oral anticoagulants, the problem of recurrences or the key risk factors identified in these subjects. This document reflects the first 21, referring to the areas of: diagnosis, evaluation and treatment of primary APS. The document provides a table of recommendations and treatment algorithms.

CONCLUSIONS

An update of the SER recommendations on APS is presented. This document corresponds to partI, related to diagnosis, evaluation and treatment. These recommendations are considered tools for decision-making for clinicians, taking into consideration both the decision of the physician experienced in APS and the patient. A partII has also been prepared, which addresses aspects related to obstetric SAF and special situations.

[Seronegative antiphospholipid syndrome: Myth or reality?]

The antiphospholipid syndrome (APS) is a systemic autoimmune disease characterized by thrombosis and/or obstetrical manifestations and the persistent presence, at least 12 weeks apart, of antiphospholipid antibodies (aPL) such as lupus anticoagulant (LA) and/or anticardiolipin antibodies (ACL) and/or anti-β2 glycoprotein I antibodies (aβ2GPI). The finding of patients with clinical profile highly suggestive of APS but who are negative for conventional biological criteria has led to the concept of seronegative APS. In the last few years, new antigen targets and methodological approaches have been employed to more clearly identify this syndrome in patients with thrombosis or obstetrical complications without conventional aPL. Although seronegative APS is still controversial, there is increasing recognition of the existence of this subgroup. However, clinical relevance of non conventional aPL need to be confirmed by efforts toward standardizing new biological tools and longitudinal studies involving large cohort of patients.

"Non-criteria" antiphospholipid antibodies add value to antiphospholipid syndrome diagnoses in a large Chinese cohort

BACKGROUND

Despite expansion in the 2006 Sydney antiphospholipid syndrome (APS) classification criteria to include IgG/IgM anti-β2-glycoprotein (aβ2GPI) antibodies in addition to IgG/IgM anti-cardiolipin antibodies (aCL) and lupus anticoagulant (LAC), some individuals with clinical features of APS remain seronegative (seronegative APS or SNAPS) and are at risk of recurrent thrombosis and pregnancy morbidities. Our aim was to assess the value of "non-criteria" aPL antibodies to detect these SNAPS patients.

METHODS

One hundred ninety-two APS patients, 90 SNAPS patients, 193 autoimmune disease controls, and 120 healthy controls were evaluated. Ten antiphospholipid antibodies (aPLs) were tested using commercial kits, including 5 non-criteria aPLs: anti-phosphatidylserine/prothrombin antibodies (aPS/PT) IgG/IgM, aCL IgA, aβ2GPI IgA, and anti-β2GPI Domain 1 (aβ2GPI-D1) IgG.

RESULTS

Up to 60.9% of the SNAPS and 93.5% of APS patients were detected by at least one non-criteria aPL. aPS/PT IgG had the highest Youden index in classifying APS and SNAPS from controls. aPS/PT IgG and aβ2GPI Domain 1 IgG seem to be the most significant risk factors for thrombotic events and pregnancy morbidity, respectively. aPS/PT IgG/IgM and aβ2GPI-D1 IgG were detected in some SNAPS patients, while IgA isotypes of aCL/aβ2GPI tended to appear together with other biomarkers. The combined analysis showed enhanced diagnostic performance with the inclusion of non-criteria aPLs.

CONCLUSIONS

Recognition of SNAPS patients is critical for clinical management and prevention of potential thrombotic and obstetric adverse events. The non-criteria antiphospholipid antibodies help to identify a considerable portion (60.9%) of these patients who otherwise may remain untreated and at clinical risk.

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

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

Multiple Arterial Thrombosis in Seronegative Antiphospholipid Syndrome: Need for New Diagnostic Criteria?

Background

Antiphospholipid syndrome (APS) is defined as thromboembolic complications and/or pregnancy morbidity in the presence of persistent increased titres of antiphospholipid antibodies. Nevertheless, some patients with clinical signs suggestive of APS are negative for diagnostic antibodies and may be classified as having seronegative-APS (SN-APS). Among the ‘non-diagnostic’ antibodies, a few studies have suggested that the IgG anti-vimentin/cardiolipin antibodies (AVA/CL) may be associated with risk of thrombosis.

Aims

The aim of this case report is to encourage the assessment of non-conventional antibodies in APS.

Patient and methods: We report the case of a 69-year-old male patient with rapid onset of apparently unexplained multiple exclusively arterial thrombotic events in both coronary and peripheral vascular beds.

Results

The patient did not meet the diagnostic criteria for APS but was positive for AVA/CL, which result persisted on further testing at 3 and 6 months.

Discussion

Ongoing research has revealed the existence of non-criteria antibodies which may be relevant for the diagnosis of SN-APS and should be included in the classification criteria for the disease.

LEARNING POINTS

Does seronegative obstetric APS exist? "pro" and "cons"

Antiphospholipid Syndrome (APS) is the commonest treatable cause of recurrent miscarriage and pharmacological treatment of pregnant patients with antiphospholipid antibodies (aPL) should aim at preventing obstetric complications and maternal thrombotic events. Conventional treatment for patients with an established diagnosis of obstetric APS (OAPS), generally resulting in over 70-80% successful pregnancies. Since seropositive (SP)-APS and seronegative (SN)-APS patients had shown similar clinical profiles, patients with SN- OAPS, as well as SP-OAPS, should receive combined treatment in order to improve the pregnancy prognosis; indeed, current standard of care increased good pregnancy outcome in SN-APS, with similar effect to confirmed APS. The above data suggest that there are patients with the clinical manifestations of OAPS but persistently negative to conventional aPL that need to be identified to ensure adequate therapy and therefore a better prognosis. The clinical utility of non-criteria aPL in the diagnosis of SN-APS is still a matter of debate. In the last decade more and more studies have reported the presence of patients suffering from SN-APS in which non-conventional ("non-criteria") aPL might be present or antibodies may be detected using methodological approaches different from the traditional assays. To improve test standardization large prospective, multicenter, and multinational studies are needed. Therefore, when assessing a patient with clinical manifestations consistent with OAPS but aPL negative using the conventional available assays, the clinician should consider the possibility that the patient is affected with SN-APS.

A Fit-for-Purpose Method for the Detection of Human Antibodies to Surface-Exposed Components of BMS-986263, a Lipid Nanoparticle-Based Drug Product Containing a siRNA Drug Substance

ND-L02-s0201/BMS-986263 is a lipid nanoparticle (LNP) drug product containing a heat shock protein 47 (HSP47)-specific small interfering ribonucleic acid (siRNA) and being developed for the treatment of liver and idiopathic pulmonary fibrosis. To address immunogenicity-related issues, we developed a robust, fit-for-purpose (FFP) three-tier electrochemiluminescent (ECL) anti-drug antibody (ADA) assay for the detection of antibodies (Abs) generated to surface-exposed components of BMS-986263. The drug was coated directly on plates, and several Abs specific for polyethylene glycol (PEG) and other surface components were tested for use as positive quality controls (QCs). Following selection of a rabbit monoclonal anti-PEG Ab, the assay was optimized, and various method development challenges specific to the modality and pseudo surrogate rabbit control were addressed. Screening, confirmatory, and titer cut points were validated following a statistical evaluation of 41 individual K₂EDTA human plasma samples at a minimum required dilution (MRD) of 100. Assay precision, sensitivity, selectivity, drug tolerance, and hook effect were determined for the rabbit Ab prepared in human K₂EDTA plasma matrix. The assay was used to interrogate anti-drug Ab (ADA) responses in normal human subjects who were administered 90 mg of the drug intravenously (IV) once every week for 3 weeks in phase I clinical trials. All pre- and post-dose samples were found to be negative for ADA. Based on these results, we concluded that BMS-986263 is not immunogenic. To the best of our knowledge, this work represents the first ADA method developed and reported for an LNP-based drug product.

Role of NOD2 in antiphospholipid antibody-induced and bacterial MDP amplification of trophoblast inflammation

Women with antiphospholipid antibodies (aPL) are at high risk for pregnancy complications, such as preeclampsia. We previously demonstrated that aPL recognizing β₂GPI promote an extravillous trophoblast pro-inflammatory, anti-migratory and anti-angiogenic profile similar to that seen in preeclampsia. Since preeclampsia in the absence of aPL may have an underlying infectious element, women with aPL may be at increased risk for preeclampsia or other adverse outcomes if an infection is present. Our objective was to determine the impact the common bacterial component, muramyl dipeptide (MDP), has on trophoblast responses to aPL. Herein, we report that bacterial MDP amplifies trophoblast IL-1β expression, processing, and secretion in the presence of aPL through activation of NOD2. In the absence of MDP, NOD2 also mediates anti- β₂GPI antibody-induced trophoblast IL-1β and VEGF secretion. Additionally, we report a role for extravillous trophoblast vimentin as a novel danger signal that contributes to the aPL-induced trophoblast IL-1β production. Together our data indicate that NOD2 mediates trophoblast inflammatory and angiogenic responses to aPL alone, and mediates trophoblast inflammation in the presence of bacterial MDP. These findings suggest that a bacterial infection at the maternal-fetal interface may exacerbate the impact aPL have on trophoblast inflammation and, thus, on pregnancy outcome.

A Monocentric Cohort of Obstetric Seronegative Anti-Phospholipid Syndrome

The present study was conducted to diagnose obstetric anti-phospholipid syndrome (OAPS) in patients with clinical signs suggestive of anti-phospholipid syndrome (APS), but persistently negative for conventional anti-phospholipid antibodies (aPL). Sera from 61 obstetrical seronegative APS (SN-APS) patients were analyzed for anti-cardiolipin antibodies (aCL) using thin-layer chromatography (TLC)-immunostaining, for anti-cardiolipin/vimentin antibodies (aCL/Vim), anti-phosphatidylserine/prothrombin antibodies, IgA anti-β₂glycoprotein I antibodies (aβ₂GPI), and IgA aCL antibodies by enzyme-linked immunosorbent assay. Taken together, our findings show that in 50 out of 61 SN-APS (81.9%) at least one aPL/cofactor antibody was detected using the assays under test. Results revealed that 76% of SN-APS patients resulted positive for aCL by TLC-immunostaining, 54% for aCL/Vim, 12% for aPS/PT, 4% for IgA aβ₂GPI, and 2% for IgA aCL. Thirty-five out of 61 patients were followed up and the tests were repeated on two occasions, at least 12 weeks apart. Twenty-six out of 35 SN-APS (74.3%) were positive at least one non-conventional test; only 2 patients (5.7%) did not confirm the positivity to the second test. These findings suggest that non-conventional tests, mainly aCL/Vim and aCL detected by TLC-immunostaining, seem to be the most sensitive approaches for finding out aPL in patients with obstetric SN-APS. The use of these tests can be useful for accurate and timely diagnosis of patients with obstetrical APS who are negative for conventional laboratory criteria markers.

Clinical Risk Assessment in the Antiphospholipid Syndrome: Current Landscape and Emerging Biomarkers

PURPOSE OF REVIEW

Laboratory criteria for the classification of antiphospholipid syndrome include the detection of a lupus anticoagulant and/or anticardiolipin and anti-β2-glycoprotein I antibodies. However, the majority of patients who test positive in these assays do not have thrombosis. Current risk-stratification tools are largely limited to the antiphospholipid antibody profile and traditional thrombotic risk factors.

RECENT FINDINGS

Novel biomarkers that correlate with disease activity and potentially provide insight into future clinical events include domain 1 specific anti-β₂GPI antibodies, antibodies to other phospholipids or phospholipid/protein antigens (such as anti-PS/PT), and functional/biological assays such as thrombin generation, complement activation, levels of circulating microparticles, and annexin A5 resistance. Clinical risk scores may also have value in predicting clinical events. Biomarkers that predict thrombosis risk in patients with antiphospholipid antibodies have been long sought, and several biomarkers have been proposed. Ultimately, integration of biomarkers with established assays and clinical characteristics may offer the best chance of identifying patients at highest risk of APS-related complications.

Anti-mutated citrullinated vimentin antibodies in antiphospholipid syndrome: diagnostic value and relationship with clinical features

Antiphospholipid antibodies (aPLs) are a heterogeneous group of autoantibodies essential for the diagnosis of antiphospholipid syndrome (APS) but do not predict clinical manifestations or disease progression. Hence, the co-presence of other antibodies may prove useful. Autoimmunity directed toward vimentin and other citrullinated peptides was established in rheumatoid arthritis (RA) and in other autoimmune conditions including systemic lupus erythematosus (SLE). We have previously described the presence of autoantibodies directed against vimentin/cardiolipin complex in patients with antiphospholipid syndrome (APS), but there are no data on the role of citrullinated vimentin in APS. Thus, we evaluated the prevalence and clinical significance of anti-MCV in APS patients. The study group consisted of 79 unselected outpatients with APS. Control groups included 25 patients with SLE, 30 patients with RA, and 20 healthy subjects age- and sex-matched. To detect anti-MCV, anti-vimentin, anti-vimentin/cardiolipin, and anti-CCP2 antibodies, commercial or homemade enzyme-linked immunosorbent assays (ELISA) were performed. Anti-MCV antibodies were found in a high percentage of APS patients (26.6%). A significant correlation between anti-MCV and anti-vimentin/cardiolipin serum levels was observed (p = 0.029). Moreover, vimentin reactivity was increased by its citrullination or conjugation with cardiolipin (p = 0.01 and p < 0.001, respectively). Interestingly, anti-MCV was found associated with the presence of arthritis (p = 0.011) and anti-vimentin/cardiolipin was highly specific for the presence of arterial or venous thrombosis in APS (p = 0.003 and p = 0.002, respectively). The detection of additional autoantibodies may contribute to clinical assessment of APS patients. Citrullination may occur in APS and play a role in the pathogenesis of this condition.

KEY POINTS

•Anti-MCV antibodies can be found in APS patients and are associated with the presence of arthritis. •Anti-vimentin/cardiolipin is strongly associated with the presence of thrombosis (both arterial and venous). •Citrullination occurs in APS, participate in disease pathogenesis, and influence clinical picture.

Protein array autoantibody profiles to determine diagnostic markers for neuropsychiatric systemic lupus erythematosus

Objective

The aim was to investigate the association between autoantibodies (autoAbs) and neuropsychiatric (NP) involvement in patients with SLE and to evaluate whether any autoAb or a combination of these autoAbs could indicate the underlying pathogenic process.

Methods

Using a multiplexed protein array for 94 antigens, we compared the serum autoAb profiles of 69 NPSLE patients, 203 SLE patients without NP involvement (non-NPSLE) and 51 healthy controls. Furthermore, we compared the profiles of NPSLE patients with clinical inflammatory (n = 38) and ischaemic (n = 31) NP involvement.

Results

In total, 75 IgG and 47 IgM autoAbs were associated with SLE patients in comparison with healthy controls. Comparing NPSLE with non-NPSLE and healthy control sera, 9 IgG (amyloid, cardiolipin, glycoprotein 2, glycoprotein 210, heparin, heparan sulphate, histone H2A, prothrombin protein and vimentin) and 12 IgM (amyloid, cardiolipin, centromere protein A, collagen II, histones H2A and H2B, heparan sulphate, heparin, mitochondrial 2, nuclear Mi-2, nucleoporin 62 and vimentin) autoAbs were present at significantly different levels in NPSLE. The combination of IgG autoAbs against heparan sulphate, histone H2B and vimentin could differentiate NPSLE from non-NPSLE (area under the curve 0.845, 99.97% CI: 0.756, 0.933; P < 0.0001). Compared with non-NPSLE, four IgG and seven IgM autoAbs were significantly associated with inflammatory NPSLE. In ischaemic NPSLE, three IgG and three IgM autoAbs were significantly different from non-NPSLE patients.

Conclusion

In our cohort, the presence of high levels of anti-heparan sulphate and anti-histone H2B combined with low levels of anti-vimentin IgG autoAbs is highly suggestive of NPSLE. These results need to be validated in external cohorts.

Primary thromboprophylaxis with low-dose aspirin and antiphospholipid antibodies: Pro's and Con's

Whether primary prophylaxis should be prescribed in individuals with antiphospholipid antibodies (aPL) remains controversial due to the lack of relevant evidence-based data. Indeed, it is unclear whether the benefit of LDA outweighs the risk of major bleeding associated with LDA in a low-risk population. On the contrary, stratification of aPL-positive subjects according to their aPL profile (combination, isotype and titer), presence of other concomitant risk factors for thrombosis and coexistence of an underling autoimmune disease is essential to decide whether primary prophylactic therapy should be prescribed. Additionally, the management of modifiable thrombotic risk factors is a necessary strategy, and the use of transient prophylaxis is crucial during high-risk periods. Specifically designed prospective trials are urgently needed to determine the real prophylactic impact of aspirin, as well as of alternative or concomitant therapeutic strategies such as hydroxychloroquine, statins or DOACS in aPL positive patients.

Closing the Serological Gap in the Antiphospholipid Syndrome: The Value of "Non-criteria" Antiphospholipid Antibodies

OBJECTIVE

Most clinicians use the 2006 Sydney classification criteria to evaluate patients suspected of having antiphospholipid syndrome (APS). Although sensitive and specific for APS, many patients fulfilling clinical criteria for the syndrome are persistently negative for the specific serological tests ("laboratory criteria"). These "seronegative APS" (SN-APS) patients can go undiagnosed and untreated until they experience serious clinical events. This study's objective was to describe antibody profiles of SN-APS patients using non-criteria markers, assess the clinical utility of these markers separately and in combination, and suggest incorporation into guidelines for patients suspected of APS.

METHODS

We categorized 175 consecutive patients suspected of APS into 2 subgroups: 107 fulfilling Sydney APS classification for seropositive APS (SP-APS) and 68 with clinical manifestations suggestive of APS but having negative serology, on 2 occasions, for criteria markers (SN-APS). On study inclusion, samples were retested for criteria and 11 non-criteria markers, including antiphosphatidylserine/prothrombin antibodies.

RESULTS

Using 4 of 11 non-criteria tests, a cumulative 30.9% of SN-APS patients were detected. Combining results of all 11 non-criteria tests, 25 SN-APS (36.8%) and 89 SP-APS (83.2%) were positive for 1 or more non-criteria antibodies.

CONCLUSION

Failure to diagnose APS can result in severe clinical consequences. Patients displaying clinical features of APS, but negative for conventional criteria markers, should undergo additional testing for non-criteria biomarkers. In our cohort, around one-third of SN-APS patients showed reactivity to 1 or more non-criteria markers. An update to the current classification criteria incorporating new serological markers should be considered to identify and stratify patients with APS for more effective treatment and management.

Mitochondria Initiate and Regulate Sarcopenia

We present the hypothesis that an accumulation of dysfunctional mitochondria initiates a signaling cascade leading to motor neuron and muscle fiber death and culminating in sarcopenia. Interactions between neural and muscle cells that contain dysfunctional mitochondria exacerbate sarcopenia. Preventing sarcopenia will require identifying mitochondrial sources of dysfunction that are reversible.

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

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

Diagnosis and management of the antiphospholipid syndrome

Antiphospholipid syndrome (APS) is characterized by thrombosis and/or pregnancy complications in the presence of persistent antiphospholipid antibodies (APLA). Laboratory diagnosis of APLA depends upon the detection of a lupus anticoagulant, which prolongs phospholipid-dependent anticoagulation tests, and/or anticardiolipin (aCL) and anti-β2-glycoprotein-1 (β2GPI) antibodies. APLA are primarily directed toward phospholipid binding proteins. Pathophysiologic mechanisms underlying thrombosis and pregnancy loss in APS include APLA induced cellular activation, inhibition of natural anticoagulant and fibrinolytic systems, and complement activation, among others. There is a high rate of recurrent thrombosis in APS, especially in triple positive patients (patients with lupus anticoagulant, aCL and anti-β2GPI antibodies), and indefinite anticoagulation with a vitamin K antagonist is the standard of care for thrombotic APS. There is currently insufficient evidence to recommend the routine use of direct oral anticoagulants (DOAC) in thrombotic APS. Aspirin with low molecular weight or unfractionated heparin may reduce the incidence of pregnancy loss in obstetric APS. Recent insights into the pathogenesis of APS have led to the identification of new potential therapeutic interventions, including anti-inflammatory and immunomodulatory therapies. Additional research is needed to better understand the effects of APLA on activation of signaling pathways in vascular cells, to identify more predictive biomarkers that define patients at greatest risk for a first or recurrent APLA-related clinical event, and to determine the safety and efficacy of DOACs and novel anti-inflammatory and immune-modulatory therapies for refractory APS.

Reduction of annexin A5 anticoagulant ratio identifies antiphospholipid antibody-positive patients with adverse clinical outcomes

Essentials Annexin A5 resistance is a mechanism for antiphospholipid (aPL) syndrome. 750 patients with history of thrombosis, pregnancy complications and controls were tested. Reduced annexin A5 anticoagulant ratios (A5R) correlate with aPL antibody multipositivity. Reduced A5R may identify patients with a propensity for thrombosis or pregnancy complications. Click to hear an ISTH Academy presentation on antiphospholipid antibody syndrome by Drs de Laat and Bertolaccini SUMMARY: Background Annexin A5 (A5) is a potent anticoagulant protein that shields anionic phospholipids from coagulation reactions. Previous studies showed that antibodies from patients with antiphospholipid (aPL) syndrome (APS) interfere with annexin A5 crystallization and anticoagulant activity. Objective The purpose of this study was to investigate whether reduced values in the annexin A5 anticoagulant ratio (A5R) assay (i.e. 'annexin A5 resistance') are associated with adverse clinical events in aPL antibody-positive patients. Patients/Methods In an initial discovery phase, a group of 679 patient samples from a 'real-world' tertiary care hospital population were tested for A5R. This was followed by a validation-phase cohort of 71 asymptomatic patients with aPL antibodies and no prior history of an adverse clinical event whose baseline samples were tested for A5R then subsequently observed for up to 4 years. Results In the discovery-phase group, we found a reduction of A5R in aPL antibody-positive patients with thrombosis and/or pregnancy complications compared with aPL antibody-negative patients and controls. In addition, reduced A5R values in both the discovery-phase group and validation-phase cohort correlated with the extent of multi-positivity for standard APS tests, which has also been shown to be associated with a risk of adverse clinical outcomes. Conclusion Reduced A5R values were associated with a multi-positivity profile in aPL antibody-positive patients within both groups and with the development of adverse clinical events.

Thrombotic risk assessment in antiphospholipid syndrome: the role of new antibody specificities and thrombin generation assay

Antiphospholipid syndrome (APS) is an autoimmune condition characterized by the presence of antiphospholipid antibodies (aPL) in subjects presenting with thrombosis and/or pregnancy loss. The currently used classification criteria were updated in the international consensus held in Sidney in 2005. Vascular events seem to result of local procoagulative alterations upon triggers influence (the so called “second-hit theory”), while placental thrombosis and complement activation seem to lead to pregnancy morbidity. The laboratory tests suggested by the current classification criteria include lupus anticoagulant, a functional coagulation assay, and anticardiolipin and anti-β2-glycoprotein-I antibodies, generally detected by solid phase enzyme-linked immunosorbent assay. The real challenge for treating physicians is understanding what is the actual weight of aPL in provoking clinical manifestations in each case. As thrombosis has a multi-factorial cause, each patient needs a risk-stratified approach. In this review we discuss the role of thrombotic risk assessment in primary and secondary prevention of venous and arterial thromboembolic disease in patients with APS, focusing on new antibody specificities, available risk scoring models and new coagulation assays.

Antibodies to age-β2 glycoprotein I in patients with anti-phospholipid antibody syndrome

Anti-phospholipid antibody syndrome (APS) is a systemic autoimmune disease characterized clinically by arterial and/or venous thromboses, recurrent abortions or fetal loss and serologically by the presence of 'anti-phospholipid antibodies' (aPL). The main target antigen of the antibodies is β2 glycoprotein I (β2 GPI). Post-translational oxidative modifications of the protein have been widely described. In this study we aimed to analyse sera reactivity to glucose-modified β2 GPI (G-β2 GPI). Sera collected from 43 patients with APS [15 primary APS (PAPS) and 28 APS associated with systemic lupus erythematosus (SLE) (SAPS)], 30 with SLE, 30 with rheumatoid arthritis (RA) and 40 healthy subjects were analysed by an enzyme-linked immunosorbent assay (ELISA) using a G-β2 GPI. Nine of 15 consecutive PAPS out-patients (60%) and 16 of 28 SAPS (57.1%) showed serum antibodies [immunoglobulin (Ig)G class] against G-β2 GPI (anti-G-β2 GPI) by ELISA. The occurrence of anti-G-β2 GPI was significantly higher in APS patients compared to patients suffering from SLE. No RA patients or control healthy subjects resulted positive for anti-G-β2 GPI. Of note, aG-β2 GPI prompted to identify some APS patients (four PAPS and seven SAPS), who were negative in the classical anti-β2 GPI test. Moreover, in APS patients, anti-G-β2 GPI titre was associated significantly with venous thrombosis and seizure in APS patients. This study demonstrates that G-β2 GPI is a target antigen of humoral immune response in patients with APS, suggesting that β2 GPI glycation products may contain additional epitopes for anti-β2 GPI reactivity. Searching for these antibodies may be useful for evaluating the risk of clinical manifestations.

The chronic damage in systemic lupus erythematosus is driven by flares, glucocorticoids and antiphospholipid antibodies: results from a monocentric cohort

OBJECTIVES

Literature data suggest a significantly higher mortality in patients affected by systemic lupus erythematosus (SLE) developing chronic damage. Therefore, damage prevention is a major goal in the management of SLE patients. In the present study, we assessed damage by means of the Systemic Lupus International Collaborative Clinics/American College of Rheumatology (SLICC/ACR) damage index (SDI), in a large cohort of SLE patients. Additionally, we aimed at evaluating its association with demographic and clinical features as well as with disease activity and laboratory findings.

PATIENTS AND METHODS

We enrolled consecutive patients affected by SLE diagnosed according to the American College of Rheumatology (ACR) 1997 revised criteria. Chronic damage was determined by SDI calculated at the last examination in all patients with at least six months of follow-up. Disease activity was assessed by the Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K); flare was defined as an increase of SLEDAI-2K ≥ 4 compared with the previous visit.

RESULTS

We evaluated 349 SLE patients (M/F 25/324, mean age ± SD 42.7 ± 12.4 years, mean disease duration ± SD 164.9 ± 105.2 months). Among the enrolled patients, 125 (35.8%) showed a SDI ≥ 1 (mean SDI ± SD 1.7 ± 0.9, range 0-5). The musculo-skeletal was the most frequently involved organ/system in SDI score (41/349 patients, 11.7%), with deforming/erosive arthritis in 21/349 (6.0%). The presence of chronic damage was associated with age (P < 0.001), disease duration (P < 0.001), number of flares (P = 0.02) and with the use of glucocorticoids (P = 0.02). The logistic regression analysis revealed the association between neuropsychiatric damage and antiphospholipid syndrome (P = 0.01, OR = 3.9) and between the presence of cardiovascular damage and anti-β2GPI antibodies (P = 0.01, OR 6.2).

CONCLUSIONS

In the present study chronic damage was identified in about one third of SLE patients. The association between SDI and the number of flares claim for a thigh-control of the disease activity in order to prevent the chronic damage. The possible role of antiphospholipid antibodies (aPL) in the development of neuropsychiatric and cardiovascular damage may suggest a more careful assessment of such aPL positive patients.

Altered Traffic of Cardiolipin during Apoptosis: Exposure on the Cell Surface as a Trigger for "Antiphospholipid Antibodies"

Apoptosis has been reported to induce changes in the remodelling of membrane lipids; after death receptor engagement, specific changes of lipid composition occur not only at the plasma membrane, but also in intracellular membranes. This paper focuses on one important aspect of apoptotic changes in cellular lipids, namely, the redistribution of the mitochondria-specific phospholipid, cardiolipin (CL). CL predominantly resides in the inner mitochondrial membrane, even if the rapid remodelling of its acyl chains and the subsequent degradation occur in other membrane organelles. After death receptor stimulation, CL appears to concentrate into mitochondrial “raft-like” microdomains at contact sites between inner and outer mitochondrial membranes, leading to local oligomerization of proapoptotic proteins, including Bid. Clustering of Bid in CL-enriched contacts sites is interconnected with pathways of CL remodelling that intersect membrane traffic routes dependent upon actin. In addition, CL association with cytoskeleton protein vimentin was observed. Such novel association also indicated that CL molecules may be expressed at the cell surface following apoptotic stimuli. This observation adds a novel implication of biomedical relevance. The association of CL with vimentin at the cell surface may represent a “new” target antigen in the context of the apoptotic origin of anti-vimentin/CL autoantibodies in Antiphospholipid Syndrome.

Ultrasonographic Evaluation of Resistive Index and Renal Artery Stenosis in Patients with Anti-Phospholipid Syndrome: Two Distinct Mechanisms?

Renal involvement in anti-phospholipid syndrome (APS) is still relatively unknown and probably underestimated. The described lesions consist of renal artery stenosis (RAS), venous renal thrombosis and glomerular lesions. The resistive index (RI) of intra-renal arteries, expression of the degree of vascular resistance, has been analyzed in different nephropathies and observed to be associated with functional parameters and some histologic features. In contrast, there are no studies on patients with APS. We evaluated the presence of a pathologic RI and RAS in a cohort of patients with APS. The study protocol included ultrasonographic assessment to measure the RI (RIs >0.7 were considered pathologic) and to determine the presence of RAS. We enrolled 36 patients with APS, 13 with primary APS and 23 with the form associated with systemic lupus erythematosus (SLE, secondary APS). As controls, we enrolled 10 anti-phospholipid antibody carriers, 10 patients with SLE without renal involvement and 14 age- and sex-matched healthy patients. A pathologic RI was identified in five patients with APS (13.9%) and in none of the anti-phospholipid antibody carriers (p = 0.00007). Four of the five (80%) patients with a pathologic RI had secondary APS. Three patients, all with primary APS, had RAS. The almost exclusive association of a pathologic RI with secondary APS and of RAS with primary APS suggests the involvement of two pathogenic pathways in the development of these different manifestations. The hypercoagulability status driven by APS could play a central role in the determination of RAS in patients with primary APS, whereas the activation of mTORC (mammalian target of rapamycin complex) pathways could be the pathogenic mechanism inducing development of a pathologic RI.

Current treatment of antiphospholipid syndrome: lights and shadows

For patients with antiphospholipid syndrome (APS), the consensus is to treat those who develop thrombosis with long-term oral anticoagulation therapy and to prevent obstetric manifestations by use of aspirin and heparin. These recommendations are based on data from randomized controlled trials and observational studies. Despite this body of knowledge, areas of uncertainty regarding the management of APS exist where evidence is scarce or nonexistent. In other words, for a subset of patients the course of management is unclear. Some examples are patients with 'seronegative' APS, those who do not fulfil the formal (clinical or serological) classification criteria for definite APS, and those with recurrent thrombotic events despite optimal anticoagulation. Other challenges include the treatment of clinical manifestations not included in the classification criteria, such as haematologic manifestations (thrombocytopenia and haemolytic anaemia), neurologic manifestations (chorea, myelitis and multiple sclerosis-like lesions), and nephropathy and heart valve disease associated with antiphospholipid antibodies (aPL), as well as the possible withdrawal of anticoagulation treatment in selected cases of thrombotic APS in which assays for aPL become persistently negative. This Review focuses on the current recommendations for thrombotic and obstetric manifestations of APS, as well as the management of difficult cases. Some aspects of treatment, such as secondary prophylaxis of venous thrombosis, are based on strong evidence--the 'lights' of APS treatment. Conversely, other areas, such as the treatment of non-criteria manifestations of APS, are based only on expert consensus or common sense and remain the 'shadows' of APS therapy.