Domain 5 of Beta 2 glycoprotein I: Friend or foe in health? Context matters.

Beta 2 glycoprotein I (ß2GPI) is the major autoantigen in the antiphospholipid syndrome, an autoimmune disorder characterized by thrombotic and obstetric complications. The autoantibodies that target beta 2 glycoprotein I are pathogenic and contribute to disease pathogenesis. The ß2GPI molecule is composed of 5 domains that are numbered 1 through to 5. Autoantibodies bind mainly to domain 1 whereas the majority of the biological functions of the ß2GPI molecule in diverse processes such as apoptotic cell clearance, complement regulation, lipopolysaccharide clearance and anticoagulation have been localised to domain 5 and its unique biochemistry, reviewed in this article. The role of purified domain 5 peptide as a potential therapeutic agent in APS and ischemia reperfusion injury is discussed.

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

Antibodies against phospholipid (aPL)-binding proteins, in particular, beta 2 glycoprotein I (ß2GPI), are diagnostic/classification and pathogenic antibodies in antiphospholipid syndrome (APS). ß2GPI-aPL recognize their target on endothelium and trigger a pro-thrombotic phenotype which is amplified by circulating monocytes, platelets and neutrophils. Complement activation is required as supported by the lack of aPL-mediated effects in animal models when the complement cascade is blocked. The final result is a localized clot. A strong generalized inflammatory response is associated with catastrophic APS, the clinical variant characterized by systemic thrombotic microangiopathy. A two-hit hypothesis was suggested to explain why persistent aPL are associated with acute events only when a second hit allows antibody/complement binding by modulating ß2GPI tissue presentation. ß2GPI/ß2GPI-aPL are also responsible for obstetric APS, being the molecule physiologically present in placental/decidual tissues. Additional mechanisms mediated by aPL with different characteristics have been reported, but their diagnostic/prognostic value is still a matter of research.

Viewpoint: The value of non-criteria antiphospholipid antibodies.

In 2006, at a meeting in Sydney, Australia, consensus was reached by an international group of specialists to establish a number of serological criteria that identify patients with a history of thrombosis or pregnancy complications as having antiphospholipid syndrome (APS). These criteria were originally formulated for research purposes and to compare clinical trials in different centres. However, these same criteria are now generally used and accepted for the diagnosis and treatment of patients. The practice of using these criteria for direct patient care requires that these criteria are based on sound scientific evidence. Indeed, for all the autoantibodies that are officially included in the serological criteria, it has been shown that they induce thrombosis and fetal loss when infused into mice. There are also a number of additional autoantibodies that have been identified in these patients but for these antibodies there was not enough evidence to meet the official APS criteria in 2006. Seventeen years have now passed since the consensus meeting, therefore, this review examines whether additional studies performed with these 'non-criteria' autoantibodies have provided sufficient results to suggest the inclusion of these autoantibodies in the official serological criteria of APS.

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

OBJECTIVES: Our primary objective was to quantify damage burden measured by Damage Index for Antiphospholipid Syndrome (DIAPS) in aPL-positive patients with or without a history of thrombosis in an international cohort (the APS ACTION cohort). Secondly, we aimed to identify clinical and laboratory characteristics associated with damage in aPL-positive patients. METHODS: In this cross-sectional study, we analysed the baseline damage in aPL-positive patients with or without APS classification. We excluded patients with other autoimmune diseases. We analysed the demographic, clinical and laboratory characteristics based on two subgroups: (i) thrombotic APS patients with high vs low damage; and (ii) non-thrombotic aPL-positive patients with vs without damage. RESULTS: Of the 826 aPL-positive patients included in the registry as of April 2020, 586 with no other systemic autoimmune diseases were included in the analysis (412 thrombotic and 174 non-thrombotic). In the thrombotic group, hyperlipidaemia (odds ratio [OR] 1.82; 95% CI 1.05, 3.15; adjusted P = 0.032), obesity (OR 2.14; 95% CI 1.23, 3.71; adjusted P = 0.007), aß2GPI high titres (OR 2.33; 95% CI 1.36, 4.02; adjusted P = 0.002) and corticosteroid use (ever) (OR 3.73; 95% CI 1.80, 7.75; adjusted P < 0.001) were independently associated with high damage at baseline. In the non-thrombotic group, hypertension (OR 4.55; 95% CI 1.82, 11.35; adjusted P = 0.001) and hyperlipidaemia (OR 4.32; 95% CI 1.37, 13.65; adjusted P = 0.013) were independent predictors of damage at baseline; conversely, single aPL positivity was inversely correlated with damage (OR 0.24; 95% CI 0.075, 0.77; adjusted P = 0.016). CONCLUSIONS: DIAPS indicates substantial damage in aPL-positive patients in the APS ACTION cohort. Selected traditional cardiovascular risk factors, steroids use and specific aPL profiles may help to identify patients more prone to present with a higher damage burden.

Thrombosis and antiphospholipid antibodies in Japanese COVID-19: based on propensity score matching.

Background: Thrombosis is a unique complication of coronavirus disease 2019 (COVID-19). Although antiphospholipid antibodies (aPL) are detected in COVID-19 patients, their clinical significance remains elusive. We evaluated the prevalence of aPL and serum concentrations of beta-2 glycoprotein I (ß2GPI), a major self-antigen for aPL, in Japanese COVID-19 patients with and without thrombosis. Methods: This retrospective single-center nested case-control study included 594 hospitalized patients with COVID-19 between January 2020 and August 2021. Thrombotic complications were collected from medical records. Propensity score-matching method (PSM) (1:2 matching including age, sex, severity on admission, and prior history of thrombosis) was performed to compare the prevalence and titer of aPL (anti-cardiolipin (aCL) IgG/IgM, anti-ß2GPI IgG/IgM/IgA, and anti-phosphatidylserine/prothrombin antibody (aPS/PT) IgG/IgM) and serum ß2GPI concentration. In addition, PSM (1:1 matching including age and sex) was performed to compare the serum ß2GPI concentration between COVID-19 patients and healthy donors. Results: Among the patients, 31 patients with thrombosis and 62 patients without were compared. The prevalence of any aPLs was indifferent regardless of the thrombosis (41.9% in those with thrombosis vs. 38.7% in those without, p =0.82). The positive rates of individual aPL were as follows: anti-CL IgG (9.7% vs. 1.6%, p =0.11)/IgM (0% vs. 3.2%, p =0.55), anti-ß2GP1 IgG (22.6% vs. 9.7%, p =0.12)/IgA (9.7% vs. 9.7%, p =1.0)/IgM (0% vs. 0%, p =1.0), and anti-PS/PT IgG (0% vs. 1.6%, p =1.0)/IgM (12.9% vs. 21.0%, p =0.41), respectively. The aPL titers were also similar regardless of thrombosis. The levels of ß2GPI in COVID-19 patients were lower than those in the healthy donors. Conclusion: Although aPLs were frequently detected in Japanese COVID-19 patients, their prevalence and titer were irrelevant to thrombotic complications. While COVID-19 patients have lower levels of serum ß2GPI than healthy blood donors, ß2GPI levels were indifferent regardless of thrombosis. Although most of the titers were below cut-offs, positive correlations were observed among aPLs, suggesting that the immune reactions against aPL antigens were induced by COVID-19. We should focus on the long-term thromboembolic risk and the development of APS in the aPL-positive patients with high titer or multiple aPLs.

Interaction of the antiphospholipid syndrome autoantigen beta-2 glycoprotein I with DNA and neutrophil extracellular traps.

Beta-2 glycoprotein I (ß2GPI) is a phospholipid-binding plasma protein and prominent autoantigen in antiphospholipid syndrome (APS). Here, we tested the hypothesis that ß2GPI might bind to not only phospholipids, but also cell-free DNA and neutrophil extracellular traps (NETs). We report that ß2GPI interacts with cell-free DNA from different species, as well as NETs, in a dose-dependent manner, retarding their migration in an agarose-gel electrophoretic mobility shift assay. We confirm the direct binding interaction of ß2GPI with DNA and NETs by ELISA. We also demonstrate that ß2GPI colocalizes with NET strands by immunofluorescence microscopy. Finally, we provide evidence that ß2GPI-DNA complexes can be detected in the plasma of APS patients, where they positively correlate with an established biomarker of NET remnants. Taken together, our findings indicate that ß2GPI interacts with DNA and NETs, and suggest that this interaction may play a role as a perpetuator and/or instigator of autoimmunity in APS.

Anti-C1q antibodies in lupus nephritis children with glomerular microthrombosis.

AIM: Glomerular microthrombosis (GMT) was a common vascular lesion in patients with lupus nephritis (LN). The objective of this study was to investigate the relationship between serum anti-beta2-glycoprotein I antibodies (a-ß2GP1) and anti-complement 1q antibodies (a-C1q) antibodies and to investigate the possible mechanism of GMT in children with LN. METHODS: The subjects were 191 children with LN diagnosed by renal biopsy in our hospital from January 2017 to January 2020. The patients were divided into GMT group and non-GMT group. The clinical manifestations, laboratory tests, renal pathology, prognosis of the two groups and the relationship between a-ß2GP1 and a-C1q antibodies were observed. RESULTS: In 191 children with LN, 52 cases (27.23%) presented with GMT. The value of C3, haemoglobin (Hb), estimate glomerular filtration rate (eGFR) and anticardiolipin antibody (ACA) in GMT group were lower than that of non-GMT group (p < .05, p < .01). The value of serum creatinine (Scr), 24 h proteinuria (PRO), urine red blood cells (RBC), N-acetyl-ß-d-glucosidase (NAG) and retinol-binding protein (RBP), a-C1q, a-ß2GP1, Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) and renal histopathological activity index (AI) score in GMT group were higher than that of non-GMT group (p < .05, p < .01). The positive proportions of serum a-C1q and a-ß2GP1 in GMT group were higher than those in non-GMT group (p < .05). According to Spearman correlation analysis, a-C1q was positively correlated with AI score, SLEDAI, a-ß2GP1, GMT, LN-III and LN-IV. Hb, eGFR and a-C1q Ab were associated with the formation of GMT in children with LN. The complete proteinuria remission and renal survival in GMT group were significantly lower than those in non-GMT group (p < .05, p < .01). CONCLUSION: LN children with GMT had more severe clinical manifestations and renal pathologic damages, and poor outcome. Serum a-C1q level was positively correlated with a-ß2GP1, and a-ß2GP1 may be involved in the formation of GMT in children with LN, which might involve in the activation of complement classical pathway.

Cysteine and methionine oxidation in thrombotic disorders.

Thrombosis is the leading cause of death in many diseased conditions. Oxidative stress is characteristic of these conditions. Yet, the mechanisms through which oxidants become prothrombotic are unclear. Recent evidence suggests protein cysteine and methionine oxidation as prothrombotic regulators. These oxidative post-translational modifications occur on proteins that participate in the thrombotic process, including Src family kinases, protein disulfide isomerase, ß2 glycoprotein I, von Willebrand factor, and fibrinogen. New chemical tools to identify oxidized cysteine and methionine proteins in thrombosis and hemostasis, including carbon nucleophiles for cysteine sulfenylation and oxaziridines for methionine, are critical to understanding why clots occur during oxidative stress. These mechanisms will identify alternative or novel therapeutic approaches to treat thrombotic disorders in diseased conditions.

Laboratory Testing for Non-criteria Antiphospholipid Antibodies: Antibodies Toward the Domain I of Beta2-Glycoprotein I (aDI).

Anti-ß2GPI antibodies (aß2GPI) are one of the laboratory criteria for antiphospholipid syndrome (APS), along with lupus anticoagulant (LA) and anticardiolipin antibodies (aCL). A subset of the aß2GPI are the antibodies directed toward the domain I of the ß2GPI (aDI). The aDI are regarded as non-criteria aPL and are among the most studied non-criteria aPL. Antibodies directed against a specific epitope in the domain I (G40-R43) of ß2GPI were shown to be strongly correlated with thrombotic and obstetric events in APS. Many studies illustrated the pathogenic capacity of these antibodies, although with various results, depending on the assay used. The first studies were performed with an in-house ELISA with high specificity for aDI toward the G40-R43 epitope. More recently, a commercial chemiluminescence immunoassay for aDI IgG became obtainable for diagnostic laboratories. Although the added value of aDI on top of the criteria aPL is not clear, with opposing findings in literature, the assay might help in the diagnosis of APS, identifying the patients at risk since aDI are frequently present with high titers in triple-positive patients (positive for LA, aß2GPI, and aCL). aDI can be used as a confirmatory test and is useful for proving the specificity of the aß2GPI antibodies. In this chapter, the procedure for detecting these antibodies is outlined, using an automated chemiluminescence assay which can be used to determine the presence of IgG aDI in human samples. General guidelines that will facilitate optimal performance of the aDI assay are also provided.

Case Report: Optic neuritis as the initial presentation of Orientia tsutsugamushi infection detected by metagenomic next-generation sequencing.

Scrub typhus is an acute febrile illness caused by Orientia tsutsugamushi infection, and typically manifested as fever, eschar, lymphadenopathy, rash, and other flu-like signs. Ocular involvement was not uncommon, and mostly occurred at post-fever or recovery stage in scrub typhus cases. We hereby report a case of scrub typhus presenting as unilateral optic neuritis (ON). A 56-year-old man going wild fishing nearly every day complained of a blurred vision and an inferior visual field defect in the right eye two or three days after an insect-bite like shin induration in his left leg. He was diagnosed as ON, and treated with dexamethasone in the local hospital. Unfortunately, his right eye vision progressively deteriorated during steroid therapy. Three days after steroid therapy ceased, he suffered from a high fever and painful subcutaneous masses in the left groin. Peripheral blood test by metagenomic next-generation sequencing (mNGS) was positive for Orientia tsutsugamushi, but negative for other pathogens. The diagnosis was then revised to scrub typhus and ON. His systemic symptoms rapidly disappeared after oral doxycycline and omadacycline therapy. However, his right eye vision continuously deteriorated to hand motion. Further serum tests for aquaporin 4-IgG antibody and myelin oligodendrocyte glycoprotein-IgG antibody were both negative, but for anticardiolipin IgM and beta-2-glycoprotein-I IgM were both positive. The patient's right eye vision gradually improved after doxycycline combined with steroid pulse therapy. Our case indicates that ON in scrub typhus cases may present as a parainfectious inflammation, and that mNGS is a useful and valuable method for early diagnosis of scrub typhus.

Anticardiolipin and anti-beta 2-glycoprotein I antibodies in patients with unexplained articular manifestations.

OBJECTIVE: To determine the frequency of antiphospholipid antibodies (aPL) in patients with unexplained articular manifestations. MATERIAL AND METHODS: Three hundred thirteen patients suffering from arthritis or arthralgia without evident cause and 266 healthy blood donors (HBD) were included in the study. Anticardiolipin antibodies (aCL) and anti-beta 2-glycoprotein I antibodies (aß2GPI) were measured by ELISA. RESULT: Out of the 313 patients, 250 were females and 63 were males. The mean age of patients was 49 ± 14 years (17-87 years). One hundred eleven patients have arthralgia and 202 have arthritis. The frequency of aCL and/or aß2 GPI (24.9%) was significantly higher in patients than in HBD (10.9%). The frequency of aß2GPI was 23.6% in patients and 9.4% in the control group (p < 10-3 ). aß2GPI-IgA was significantly more frequent in patients than in the control group (20.4% vs. 7.5%, p < 10-3 ). aß2GPI was most commonly observed than aCL in patients (23.6% vs. 6.4%, p < 10-6 ). IgA isotype of aß2GPI was the most frequent in 20.4% of patients while IgG and IgM were detected in 5.4% and 2.9% respectively. CONCLUSION: This study showed that aPL were common in patients with articular manifestations and were mainly directed against ß2 GPI. The role of these antibodies remains to be specified.

Frequency of positive antiphospholipid antibodies in pregnant women with SARS-CoV-2 infection and impact on pregnancy outcome: A single-center prospective study on 151 pregnancies.

Background: At the beginning of the SARS-CoV-2 pandemic, there was a lack of information about the infection's impact on pregnancy and capability to induce de novo autoantibodies. It soon became clear that thrombosis was a manifestation of COVID-19, therefore the possible contribution of de novo antiphospholipid antibodies (aPL) raised research interest. We aimed at screening SARS-CoV-2 positive pregnant patients for aPL. Methods: The study included consecutive pregnant women who were hospitalized in our Obstetric Department between March 2020 and July 2021 for either a symptomatic SARS-CoV-2 infection or for other reasons (obstetric complications, labour, delivery) and found positive at the admission nasopharyngeal swab. All these women underwent the search for aPL by means of Lupus Anticoagulant (LA), IgG/IgM anti-cardiolipin (aCL), IgG/IgM anti-beta2glycoprotein I (aB2GPI). Data about comorbidities, obstetric and neonatal complications were collected. Results: 151 women were included. Sixteen (11%) were positive for aPL, mostly at low titre. Pneumonia was diagnosed in 20 women (5 with positive aPL) and 5 required ICU admission (2 with positive aPL). Obstetric complications occurred in 10/16 (63%) aPL positive and in 36/135 (27%) negative patients. The occurrence of HELLP syndrome and preeclampsia was significantly associated with positive aPL (p=0,004). One case of maternal thrombosis occurred in an aPL negative woman. aPL positivity was checked after at least 12 weeks in 7/16 women (44%): 3 had become negative; 2 were still positive (1 IgG aB2GPI + IgG aCL; 1 IgM aB2GPI); 1 remained positive for IgG aCL but became negative for aB2GPI; 1 became negative for LA but displayed a new positivity for IgG aCL at high titre. Conclusions: The frequency of positive aPL in pregnant women with SARS-CoV-2 infection was low in our cohort and similar to the one described in the general obstetric population. aPL mostly presented as single positive, low titre, transient antibodies. The rate of obstetric complications was higher in aPL positive women as compared to negative ones, particularly hypertensive disorders. Causality cannot be excluded; however, other risk factors, including a full-blown picture of COVID-19, may have elicited the pathogenic potential of aPL and contributed themselves to the development of complications.

Antiphospholipid syndrome: Reversal of antiphosphatidylserine/prothrombin-induced activated protein C resistance.

BACKGROUND: Anti-phosphatidylserine/prothrombin (aPS/PT) antibodies are the major contributor to activated Protein C resistance (APC-R) in tetra-positive thrombotic high-risk patients with Antiphospholipid Syndrome (APS). OBJECTIVES: To evaluate the role of phospholipids (PL) on aPS/PT mediated APC-R. PATIENTS/METHODS: Total IgG were purified from plasma of 6 tetra-positive patients and IgG aPS/PT were affinity-purified from 3 of these patients. Purified material was spiked into Normal Pooled Plasma (NPP) and tested for APC-R in thrombin generation assay and in Factor Va inactivation assay using increasing amounts of phospholipids. RESULTS AND CONCLUSIONS: Total IgG showed APC-R at low PL concentration (1.5 µg/mL) that disappeared at increasing PL concentrations (5.8, 11.6 and 46.6 µg/mL). In the same way, affinity purified aPS/PT showed a robust (59 %, 52 %, 36 %) APC-R in patients #4, #5 and #6, respectively at low PL concentration (1.5 µg/mL) that was completely reversed at higher concentration (11.6 µg/mL). The inactivation of FVa by activated Protein C (aPC) was impaired in the presence of aPS/PT at low aPL concentration and reversed by increasing amounts of PL. These data point out the relevance of PL in reversing APC-R in this 'in vitro' system. The mechanism for reversal might be explained by loss of PL availability for aPC. These results may give some insight into the pathogenesis of thrombosis or suggestions for alternative treatments.

Teriflunomide normalizes anti-anxiety effect in anti-ANXA2 APS mice model teriflunomide in anti-ANXA2 mice model.

Antiphospholipid syndrome (APS) affects the brain by both hypercoagulation and immunological mechanisms. APS is characterized by several autoantibodies binding to a thrombolytic complex including beta-2-glycoprotein I (ß2-GPI) and annexin A2 (ANXA2). Teriflunomide, an oral drug for the treatment of multiple sclerosis (MS), has a cytostatic effect on B cells and is therefore a potential antibody-targeting treatment for APS. In this study, we assessed the effect of teriflunomide in two APS mouse models by inducing autoantibody formation against ß2-GPI and ANXA2 in female BALB/c mice. The ANXA2 model displayed a behavioral change suggesting an anti-anxiety effect in open field and forced swim tests, early in the course of the disease. This effect was normalized following teriflunomide treatment. Conversely, behavioral tests done later during the study demonstrated depression-like behavior in the ANXA2 model. No behavioral changes were seen in the ß2-GPI model. Total brain IgG levels were significantly elevated in the ANXA2 model but not in the teriflunomide treated group. No such change was noted in the brains of the ß2-GPI model. High levels of serum autoantibodies were induced in both models, and their levels were not lowered by teriflunomide treatment. Teriflunomide ameliorated behavioral changes in mice immunized with ANXA2 without a concomitant change in serum antibody levels. These findings are compatible with the effect of teriflunomide on neuroinflammation.Teriflunomide ameliorated behavioral and brain IgG levels in mice immunized with ANXA2 without a concomitant change in serum antibody levels. These findings are compatible with an effect of teriflunomide on the IgG permeability to the brain and neuroinflammation.

PEGylated Domain I of Beta-2-Glycoprotein I Inhibits Thrombosis in a Chronic Mouse Model of the Antiphospholipid Syndrome.

Antiphospholipid syndrome (APS) is an autoimmune disorder in which autoantibodies cause clinical effects of vascular thrombosis and pregnancy morbidity. The only evidence-based treatments are anticoagulant medications such as warfarin and heparin. These medications have a number of disadvantages, notably risk of haemorrhage. Therefore, there is a pressing need to develop new, more focused treatments that target the actual pathogenic disease process in APS. The pathogenic antibodies exert their effects by interacting with phospholipid-binding proteins, of which the most important is beta-2-glycoprotein I. This protein has five domains, of which the N-terminal Domain I (DI) is the main site for binding of pathogenic autoantibodies. We previously demonstrated bacterial expression of human DI and showed that this product could inhibit the ability of IgG from patients with APS (APS-IgG) to promote thrombosis in a mouse model. Since DI is a small 7kDa protein, its serum half-life would be too short to be therapeutically useful. We therefore used site-specific chemical addition of polyethylene glycol (PEG) to produce a larger variant of DI (PEG-DI) and showed that PEG-DI was equally effective as the non-PEGylated DI in inhibiting thrombosis caused by passive transfer of APS-IgG in mice. In this paper, we have used a mouse model that reflects human APS much more closely than the passive transfer of APS-IgG. In this model, the mice are immunized with human beta-2-glycoprotein I and develop endogenous anti-beta-2-glycoprotein I antibodies. When submitted to a pinch stimulus at the femoral vein, these mice develop clots. Our results show that PEG-DI inhibits production of thromboses in this model and also reduces expression of tissue factor in the aortas of the mice. No toxicity was seen in mice that received PEG-DI. Therefore, these results provide further evidence supporting possible efficacy of PEG-DI as a potential treatment for APS.

Antiphospholipid antibodies in the obstetric antiphospholipid syndrome: Detection and antibodies profile at the Maternity and Neonatal Medicine Center of Monastir, Tunisia.

PURPOSE: This study aimed to implement lupus anticoagulant (LAC) detection techniques according to the International Society on Thrombosis and Hemostasis (ISTH) recommendations, in the Biological Laboratory of the Maternity and Neonatal Medicine Center (Monastir, Tunisia) and to evaluate the profile and the prevalence of antiphospholipid antibodies (aPL) in the obstetric antiphospholipid syndrome (OAPS). METHODS: We collected two groups: a "case group" (53 women who presented one or more obstetrical criteria of APS) and a "control group." LAC was detected following the four steps recommended by ISTH 2009. Anticardiolipin (aCL) and antibeta-2-glycoprotein I (aß2GPI) antibodies testing were performed by enzyme-linked immunosorbent assay (ELISA). RESULTS: aPL were found in five patients: three patients with isolated LAC, one patient with isolated IgG aCL, and one patient with triple positivity (LAC, aCL IgM, aß2GPI IgM). Concerning LAC, 13 (24.52%) of 53 patients had a screening step with at least one positive test. The mixing step was positive in four patients and then confirmed in the confirmatory test. Thus, the prevalence of LAC in our study group is 7.54%. Surprisingly, among these positive patients, one patient had an associated combined factor V (FV) and factor VIII (FVIII) deficiency. CONCLUSION: There is no single test and no algorithm that can detect all types of LAC. It seems that the recent 2020 ISTH algorithm allows a better detection of low activity LAC than the 2009 algorithm. In our study, the most frequently identified antiphospholipid antibodies were LAC more than aCL and aß2GPI.

Βeta-2-glycoprotein I exerts antithrombotic function through its domain V in mice.

Little is known about the physiological role of beta-2-glycoprotein I (ß2GPI) despite it being the major auto-antigen in the antiphospholipid syndrome. A systematic study of the role of ß2GPI in thrombus formation in vivo has not been performed to date. Herein, we report that ß2GPI deficient (-/-) mice have enhanced thrombus formation compared to wild type (WT) mice in a laser-induced arteriole and venule model of thrombosis. Furthermore, neutrophil accumulation and elastase activity was enhanced in thrombi of ß2GPI -/- compared with WT mice. The antithrombotic function of ß2GPI is dependent on its fifth domain (domain V); intravenous administration of the ß2GPI domain deletion mutant lacking domain V (human recombinant domain I-IV) had no effect on platelet and fibrin thrombus size in ß2GPI -/- or WT mice. On the contrary, intravenous administration of human recombinant domain V significantly inhibited platelet and fibrin thrombus size in both ß2GPI -/- mice and WT mice. These findings reveal a major role for ß2GPI as a natural anticoagulant and implicate domain V of ß2GPI as a potential antithrombotic therapy.

Correlations of anti-cardiolipin antibody and anti-β2 glycoprotein I antibody with ischemic stroke in patients with systemic autoimmune diseases / 中国基层医药

Objective:To correlate anti-cardiolipin antibody (aCL) and anti-β2 glycoprotein I antibody (aβ2GPI) with ischemic stroke (IS) in patients with systemic autoimmune diseases (SADs).Methods:A total of 104 patients with SADs who received treatment in the Affiliated Hospital of North Sichuan Medical College during January to December 2019 were included in this study. They were divided into two groups whether they had IS (IS group, n = 42) or not (non-IS group, n = 62). aPL positive rate was qualitatively compared between the IS and non-IS groups. aCL and aβ2GPI expression levels were quantitatively compared between the IS and non-IS groups. Logistic regression analysis was performed to evaluate the risk factors for IS in patients with SADs. Results:aPL positive rate in the IS group was significantly higher than that in the non-IS group [61.9% (26/42) vs. 40.3% (25 /62), χ2 = 4.66, P = 0.031]. The aCL-IgM and aβ2GPI-IgM levels in the IS group were (22.82 ± 27.27) RU/mL and (18.70 ± 23.95) RU/mL, respectively, which were significantly higher than those in the non-IS group [(13.34 ± 8.43) RU/mL, (7.61± 5.80) RU/mL, t = -2.18, -2.76, P = 0.034, 0.009]. Logistic regression analysis showed that aPL is an independent risk factor for IS ( P = 0.037). Conclusion:aCL and aβ2GPI are closely related to the occurrence of IS and are the independent risk factors for IS in patients with SADs.

Differences in Endothelial Activation and Dysfunction Induced by Antiphospholipid Antibodies Among Groups of Patients With Thrombotic, Refractory, and Non-refractory Antiphospholipid Syndrome.

Antiphospholipid syndrome (APS) is an autoimmune disorder characterized by pregnancy morbidity or thrombosis and persistent antiphospholipid antibodies (aPL) that bind to the endothelium and induce endothelial activation, which is evidenced by the expression of adhesion molecules and the production of reactive oxygen species (ROS) and subsequent endothelial dysfunction marked by a decrease in the synthesis and release of nitric oxide (NO). These endothelial alterations are the key components for the development of severe pathological processes in APS. Patients with APS can be grouped according to the presence of other autoimmune diseases (secondary APS), thrombosis alone (thrombotic APS), pregnancy morbidity (obstetric APS), and refractoriness to conventional treatment regimens (refractory APS). Typically, patients with severe and refractory obstetric APS exhibit thrombosis and are classified as those having primary or secondary APS. The elucidation of the mechanisms underlying these alterations according to the different groups of patients with APS could help establish new therapies, particularly necessary for severe and refractory cases. Therefore, this study aimed to evaluate the differences in endothelial activation and dysfunction induced by aPL between patients with refractory obstetric APS and other APS clinical manifestations. Human umbilical vein endothelial cells (HUVECs) were stimulated with polyclonal immunoglobulin-G (IgG) from different groups of patients n = 21), including those with primary (VTI) and secondary thrombotic APS (VTII) and refractory primary (RI+), refractory secondary (RII+), and non-refractory primary (NR+) obstetric APS. All of them with thrombosis. The expression of adhesion molecules; the production of ROS, NO, vascular endothelial growth factor (VEGF), and endothelin-1; and the generation of microparticles were used to evaluate endothelial activation and dysfunction. VTI IgG induced the expression of adhesion molecules and the generation of microparticles and VEGF. RI+ IgG induced the expression of adhesion molecules and decreased NO production. RII+ IgG increased the production of microparticles, ROS, and endothelin-1 and reduced NO release. NR+ IgG increased the production of microparticles and endothelin-1 and decreased the production of VEGF and NO. These findings reveal differences in endothelial activation and dysfunction among groups of patients with APS, which should be considered in future studies to evaluate new therapies, especially in refractory cases.