anti-β2GP1 Antibodies Research Articles

Predicting the risk of cardiovascular and cerebrovascular event in systemic lupus erythematosus: a Chinese SLE treatment and research group study XXVI

ObjectivePatients with systemic lupus erythematosus (SLE) have an increased risk of cardiovascular and cerebrovascular events (CCEs). Furthermore, CCE was a significant factor contributing to mortality in patients with SLE. However,...

Immune thrombocytopenia in systemic lupus erythematosus: Prevalence, risk factors, and a novel predictive model for risk assessment

IntroductionImmune thrombocytopenia (ITP) is a potentially severe manifestation of systemic lupus erythematosus (SLE) reported in 7–40% of SLE patients. ITP has been associated with a higher risk of organ damage and mortality. ObjectivesTo describe which factors are associated with the presence of ITP in SLE patients. MethodsRetrospective case–control study. Cases were defined as SLE patients who had ever developed ITP and were sex- and age-matched with two controls. A predictive model was constructed to identify SLE patients who were at risk of developing ITP. ResultsITP prevalence in our SLE cohort was 8.35%. Cases had a higher frequency of hemolytic anemia, while controls had a higher prevalence of arthritis at SLE diagnosis. During SLE progression, cases tested positive for anticardiolipin, anti-β2-glycoprotein 1, and lupus anticoagulant antibodies more frequently. Cases received mycophenolic acid and azathioprine more often than controls and had a higher SLICC/ACR score. The model demonstrated a sensitivity of 87.53%, a positive predictive value of 81.92%, a specificity of 80.50%, area under the curve of 83.92%, a F1 of 83% and an overall accuracy of 83.68%. The variables that best explain the model were hemolytic anemia, arthritis, oral ulcers, Raynaud's phenomenon, low C4, low CH50, anticardiolipin and anti-β2GP1 antibodies. ConclusionSLE patients who develop ITP have a distinct phenotype characterized by more hemolytic anemia and less arthritis at SLE onset, and higher prevalence of antiphospholipid syndrome antibodies during SLE progression. This phenotype is associated with heightened organ damage and the need for more intensive therapies and stricter follow-up. Our predictive model has demonstrated an impressive ability to identify SLE patients at risk of developing ITP.

Correlation between the changes of brain amplitude of low-frequency fluctuation and cognitive impairment in patients with neuropsychiatric lupus.

To explore the relationship between brain function changes and clinical serological indicators and behavioral cognitive assessment in patients with neuropsychiatric systemic lupus erythematosus (NPSLE), and understand the pathogenesis of NPSLE from the perspective of imaging. The resting-state functional imaging data, clinical serological, and behavioral cognitive assessment scores of 28 patients with NPSLE and 22 healthy controls (HC) were prospectively collected. The resting-state amplitude of low-frequency fluctuation (ALFF) values obtained from the analysis and processing were correlated with the serological data and behavioral cognitive assessment scores to determine the relationship between these data. The average age of the patients of the NPSLE group was older than that of the HC group; significant differences in education level, Auditory Verbal Learning Test Hua Shan Version (AVLT-H), and Trail Making Test scores were observed between the two groups. The NPSLE group demonstrated increased brain activity in the insula, precentral gyrus, and superior temporal gyrus, and decreased brain activity in the superior parietal gyrus. The ALFF value of the insula positively correlated with the Anti-β2gp1 antibody and negatively correlated with the anti-nucleosome antibody and the AVL-recall (RC) score. The ALFF of the precentral gyrus negatively correlated with the AVL-immediate recall (I). The ALFF value of the superior temporal gyrus negatively correlated with the AVL-RC score. The left superior parietal gyrus positively correlated with the c-reactive protein. The right superior parietal gyrus positively correlated with the System Lupus Erythematosus Disease Activity Index and negatively correlated with the AVL-I score. Patients with NPSLE show different brain activity changes in different brain regions, and the abnormal brain regions are correlated with certain lupus antibodies, inflammatory factors, and cognitive assessment, thereby suggesting that the correlation between the three could provide novel insights into the pathogenesis of NPSLE.

Domain Specificity of Anti-Prothrombin Antibodies That Express Lupus Anticoagulant Activity

Background: The antiphospholipid syndrome (APS) is an autoimmune disorder characterized by the persistent presence of antiphospholipid antibodies (aPL). aPL are a heterogeneous group of autoantibodies directed against negatively charged phospholipids or phospholipid-binding proteins. Some of these autoantibodies exert lupus anticoagulant (LAC) activity, a laboratory phenomenon characterized by the prolongation of phospholipid-dependent coagulation tests. Recently, our group identified that LAC-positive anti-prothrombin antibodies activate platelets via the platelet receptor, FcγRIIA. However, a lot is still unclear regarding the mechanism by which these antibodies cause LAC and why some, but not all, antibodies in this heterogeneous group express LAC activity. Furthermore, experimental data on the binding site of these pathogenic anti-prothrombin antibodies are lacking. Aims: In this study we aimed to investigate the binding domain of LAC-positive monoclonal anti-prothrombin antibodies and APS patient derived anti-prothrombin antibodies. Method: Recombinant fragments of prothrombin were designed and produced in Chinese hamster ovary cells. Prothrombin fragment 1, fragment 2 and fragment 1.2 were coated on ELISA plates to study epitope specificity. Two LAC-positive monoclonal anti-prothrombin antibodies (3B1 and 28F4), two LAC-negative anti-prothrombin monoclonal antibodies (11H2 and 9C6), isolated anti-prothrombin antibodies derived from APS patients and plasma from APS patients were studied. A modified dilute Russell's viper venom time (DRVVT) test was used to evaluate whether the recombinant prothrombin constructs could neutralize the effect of LAC-positive monoclonal and patient derived anti-prothrombin antibodies. Furthermore, a fragment 1.2 nanobody was produced by immunizing Llama's followed by phage display. The ability of this nanobody to compete with LAC-positive monoclonal and patient derived anti-prothrombin antibodies for the prothrombin binding site was tested using a modified DRVVT test. Results: LAC-positive monoclonal anti-prothrombin antibodies recognized prothrombin fragment 2. Interestingly, LAC-negative anti-prothrombin antibodies bound exclusively to prothrombin fragment 1. In addition, LAC-ratios of patient samples correlated significantly with anti-fragment 2 antibody levels ( p<0.05, ρ=0.33), but not with anti-fragment 1 antibody levels. Furthermore, incubation with the prothrombin F1.2 nanobody almost completely reversed the prolonged DRVVT clotting time in plasma containing monoclonal and patient derived LAC-positive anti-prothrombin antibodies, but not in plasma containing LAC-positive anti-β2GP1 antibodies. This neutralising effect was also observed when the monoclonal anti-prothrombin antibody was incubated with prothrombin fragment 2. In contrast, the LAC-activity of anti-prothrombin antibodies was not inhibited when incubated with prothrombin fragment 1. Conclusion: Our data show that LAC-positive anti-prothrombin antibodies react with fragment 2 of prothrombin. Furthermore, a novel nanobody directed against prothrombin fragment 1.2 and prothrombin fragment 2 were able to neutralize a prothrombin-dependent LAC.

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

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. 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. 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. 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.

Circulating immune-complexes of IgG/IgM bound to B2-glycoprotein-I associated with complement consumption and thrombocytopenia in antiphospholipid syndrome.

BackgroundAntiphospholipid syndrome (APS) is a multisystemic autoimmune disorder characterized by thrombotic events and/or gestational morbidity in patients with antiphospholipid antibodies (aPL). In a previous single center study, APS-related clinical manifestations that were not included in the classification criteria (livedo reticularis, thrombocytopenia, leukopenia) were associated with the presence of circulating immune-complexes (CIC) formed by beta-2-glycoprotein-I (B2GP1) and anti-B2GP1 antibodies (B2-CIC). We have performed a multicenter study on APS features associated with the presence of B2-CIC.MethodsA multicenter, cross-sectional and observational study was conducted on 303 patients recruited from six European hospitals who fulfilled APS classification criteria: 165 patients had primary APS and 138 APS associated with other systemic autoimmune diseases (mainly systemic lupus erythematosus, N=112). Prevalence of B2-CIC (IgG/IgM isotypes) and its association with clinical manifestations and biomarkers related to the disease activity were evaluated.ResultsB2-CIC prevalence in APS patients was 39.3%. B2-CIC-positive patients with thrombotic APS presented a higher incidence of thrombocytopenia (OR: 2.32, p=0.007), heart valve thickening and dysfunction (OR: 9.06, p=0.015) and triple aPL positivity (OR: 1.83, p=0.027), as well as lower levels of C3, C4 and platelets (p-values: <0.001, <0.001 and 0.001) compared to B2-CIC-negative patients. B2-CIC of IgM isotype were significantly more prevalent in gestational than thrombotic APS.ConclusionsPatients with thrombotic events and positive for B2-CIC had lower platelet count and complement levels than those who were negative, suggesting a greater degree of platelet activation.

IgG fractions from patients with antiphospholipid syndrome and systemic lupus erythematosus bind to platelets, but do not affect collagen-induced platelet activation

ABSTRACT Anti-beta-2 glycoprotein 1 (anti-β2GP1) is an antiphospholipid antibody found in patients with antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE). Its presence commonly is associated with thrombosis; however, the mechanisms of interaction of anti-β2GP1 antibodies and platelets remain unclear. We investigated the effects of APS and SLE patient-derived IgG fractions on collagen-mediated platelet aggregation and examined the binding of patient-derived IgG to platelets before and after activation by collagen. IgG fractions, 150, 200, 300 or 350 µg/ml, isolated from 11 patients with APS and SLE were incubated with two sets of platelet-rich plasma (PRP) in the incubation wells of an aggregometer. The first set was activated by collagen and the other set was incubated for an additional 10 min. All platelets were collected by centrifugation and fixed in cell blocks. We assessed binding of IgG to platelets using immunocytochemistry (ICC). Patient-derived IgG fractions did not affect collagen-induced platelet aggregation. ICC staining using anti-human IgG antibodies demonstrated that patient-derived IgG fractions had greater affinity for non-activated platelets than those activated by 0.75 µg/ml collagen. Patient-derived IgG fractions bound to the surface of platelets and potentially could be internalized by platelets. IgG fractions from APS and SLE patients may sensitize non-activated platelets, which could increase platelet reactivity and thrombotic risk in patients. We did not detect secondary effects of patient-derived IgG fractions.

Adrenal Insufficiency Revealing a Bilateral Adrenal Hemorrhage-Adrenal Infarction Related to Antiphospholipid Syndrome

In June 2020, a 54-year-old female presented with severe fatigue that had been worsening over the past few weeks. She had a history of primary triple positive (lupus anticoagulant, anticardiolipin and anti-β2GP1 antibodies) antiphospholipid syndrome (APS) revealed 19 years ago by a venous thromboembolism, and had been long-term treated with warfarin.

Nephrotic syndrome associated with Libman–Sacks endocarditis as a first manifestation of systemic lupus

Libman–Sacks endocarditis is a rare cardiac manifestation of systemic lupus erythematosus, in which there is sterile vegetation in the heart valves with a significant risk of infective endocarditis. Patient aged 29, presents with a deep nephrotic syndrome, associated with microscopic hematuria, we find in his history a notion of inflammatory arthritis of the ankles, wrists and knees, with alteration of the general state in a long-term febrile context, associated with a chronic inflammatory left subpalpebral cellulitis. The patient was in average general condition, asthenic, with exertional dyspnoea, oedema of the lower limbs rising to the legs and the cardiac examination found a significant murmur at the aorto-mitral focus. Biologically: a deep nephrotic syndrome was found. Inflammatory syndrome with PRC at 80 mg and SR at +++. Inflammatory anaemia and lymphopenia. An echocardiography done, finds a mitro-aortic valve thickening, with the presence of fine vegetations on the aortic side of the posterior sigmoid, in addition to an important mitral and aortic leak. The immunological work-up was strongly positive for antiphospholipid syndrome with IgG anti-cardiolipin antibodies (+), IgG anti-B2GP1 antibodies (+), antinuclear factor antibodies (+) with a speckled appearance; a renal biopsy was performed and was consistent with lupus glomerulonephritis. High-dose corticosteroids combined with double antibiotic therapy significantly improved the patient's clinical and biological parameters. Our observation is quite exceptional because cardiac involvement usually occurs years after the onset of SLE, but in this observation the onset is quite nasty, first in a male subject, associating renal involvement, endocarditis and SAPL. Treatment was based on a combination of antibiotics, corticoids and synthetic antimalarials.

Hematological involvement in pediatric systemic lupus erythematosus: A multi-center study.

Introduction: Systemic lupus erythematosus (SLE) may present with features of several systems, including hematological manifestations. In this study, we aimed to evaluate the characteristics of hematological involvement and assess possible associations and correlations in pediatric SLE patients. Method: This is a retrospective multi-center study. The medical records of pediatric SLE patients followed between January 2000 and June 2020 were analyzed. All children fulfilled the criteria of the Systemic Lupus International Collaborating Clinics. Results: The study included 215 children with SLE, 118 of whom had hematological manifestations. Concomitant renal involvement and low C3 levels were significantly more frequent in patients with hematological involvement (p = 0.04, p = 0.008, respectively). Also, anti-cardiolipin, anti-beta-2-glycoprotein I (anti-β2 GP1), and anti-Sm antibody positivity, and the presence of lupus anticoagulant were more common in the group with hematological findings (p = 0.001 for anti-cardiolipin antibody positivity and p < 0.001 for the positivity of anti-β2 GP1 antibody, anti-Sm antibody, and lupus anticoagulant). The most common hematologic abnormality was anemia (n = 88, 74.5%), with autoimmune hemolytic anemia constituting the majority (n = 40). Corticosteroids followed by IVIG were the mainstay of treatment. In patients resistant to corticosteroid and IVIG treatments, the most preferred drug was rituximab. Low levels of C3, high SLEDAI score, high incidence of renal involvement, and positive antiphospholipid antibodies were associated with hematological involvement in the univariate analysis. The presence of antiphospholipid antibodies and high SLEDAI score were independently associated with hematological involvement in multivariate analysis (OR: 4.021; 95% CI: 2.041-7.921; p < 0.001 and OR: 1.136; 95% CI: 1.065-1.212; p < 0.001). Conclusion: Hematological abnormalities are frequently encountered in pediatric SLE. Positive antiphospholipid antibodies and high SLEDAI scores were associated with hematological involvement.

Assessment of Anti-β2 glycoprotein1 antibody in Systemic Lupus Erythrematosus Patients

Secondary anti-phospolipid syndrome (APS) is diagnosed in many patients with systemic lupus erythrematosus (SLE) especially with thromboembolic events and/or pregnancy loss in the presence of persistent laboratory evidence for anti-phospholipid antibody (aPL). In this work, we aimed to detect the prevalence of IgG and IgA anti-β2 glycoprotein1 (β2GP1) in SLE patients. Serum samples were collected from 50 female patients with SLE (25 had APS and 25 patients who did not have APS), in addition to 22 apparently healthy females with matched age as a control group. All samples from patients and control were tested for lupus anticoagulant (LA), IgG and IgA isotypes of antiβ2GPI, Anti-nuclear antibody (ANA), Anti-double strand antibody (Anti-dsDNA). Number of patients positive for Anti-β2GP1 antibodies were significantly increased in APS patients compared to non-APS patients (P=0.015). Anti-β2GP1 IgA isotype was significantly higher in APS patients than in non-APS patients (P=0.011) and significantly correlated with deep venous thrombosis and pregnancy morbidity (P=0.004). There was no difference in anti-β2GPI IgG isotype between APS patients and non-APS patients. We concluded that although anti-β2GPI IgA is not within Sapparo diagnostic criteria, it seems to contribute to the pathogenesis of thrombotic manifestations of SLE and may represents a useful indicator particularly when standard aPL tests are negative.

WITHDRAWN: Hematological involvement in pediatric systemic lupus erythematosus: A multi-center study.

Introduction Systemic lupus erythematosus (SLE) may present with features of several systems, including hematological manifestations. In this study, we aimed to evaluate the characteristics of hematological involvement and assess possible associations and correlations in pediatric SLE patients. Method This is a retrospective multi-center study. The medical records of pediatric SLE patients followed between January 2000 and June 2020 were analyzed. All children fulfilled the criteria of the Systemic Lupus International Collaborating Clinics. Results The study included 215 children with SLE, 118 of whom had hematological manifestations. Concomitant renal involvement and low C3 levels were significantly more frequent in patients with hematological involvement ( p = 0.04, p = 0.008, respectively). Also, anti-cardiolipin, anti-beta-2-glycoprotein I (anti-β2 GP1), and anti-Smith (anti-Sm) antibody positivity, and the presence of lupus anticoagulant were more common in the group with hematological findings ( p = 0.001 for anti-cardiolipin antibody positivity and p &lt; 0.001 for the positivity of anti-β2 GP1 antibody, anti-Sm antibody, and lupus anticoagulant). The most common hematologic abnormality was anemia ( n = 88, 74.5%), with autoimmune hemolytic anemia constituting the majority ( n = 40). Corticosteroids followed by IVIG were the mainstay of treatment. In patients resistant to corticosteroid and IVIG treatments, the most preferred drug was rituximab. The presence of antiphospholipid antibodies and high SLEDAI score were independently associated with hematological involvement in multivariate analysis (OR: 0.249; 95%CI: 0.126–0.490; p &lt; 0.001 and OR: 1.136; 95%CI: 1.065–1.212; p &lt; 0.001). Conclusion Hematological abnormalities are frequently encountered in pediatric SLE. Positive antiphospholipid antibodies and high SLEDAI scores were associated with hematological involvement.

A retrospective study on the prevalence of anti-phospholipid antibodies, thrombotic events and cutaneous signs of vasculopathy in 173 hospitalized COVID-19 patients.

BackgroundHypercoagulability is a risk factor of thromboembolic events in COVID-19. Anti-phospholipid (aPL) antibodies have been hypothesized to be involved. Typical COVID-19 dermatological manifestations of livedo reticularis and digital ischemia may resemble cutaneous manifestations of anti-phospholipid syndrome (APS).ObjectivesTo investigate the association between aPL antibodies and thromboembolic events, COVID-19 severity, mortality, and cutaneous manifestations in patients with COVID-19.MethodsaPL antibodies [anti-beta2-glycoprotein-1 (B2GP1) and anti-cardiolipin (aCL) antibodies] were titered in frozen serum samples from hospitalized COVID-19 patients and the patients’ clinical records were retrospectively analyzed.Results173 patients were enrolled. aPL antibodies were detected in 34.7% of patients, anti-B2GP1 antibodies in 30.1%, and aCL antibodies in 10.4%. Double positivity was observed in 5.2% of patients. Thromboembolic events occurred in 9.8% of patients, including 11 pulmonary embolisms, 1 case of celiac tripod thrombosis, and six arterial ischemic events affecting the cerebral, celiac, splenic, or femoral-popliteal arteries or the aorta. aPL antibodies were found in 52.9% of patients with vascular events, but thromboembolic events were not correlated to aPL antibodies (adjusted OR = 1.69, p = 0.502). Ten patients (5.8%) had cutaneous signs of vasculopathy: nine livedo reticularis and one acrocyanosis. No significant association was observed between the presence of cutaneous vasculopathy and aPL antibodies (p = 0.692).ConclusionsAnti-phospholipid antibodies cannot be considered responsible for hypercoagulability and thrombotic events in COVID-19 patients. In COVID-19 patients, livedo reticularis and acrocyanosis do not appear to be cutaneous manifestations of APS.

Latent rheumatic, thyroid and phospholipid autoimmunity in hospitalized patients with COVID-19

Autoimmune responses mediated by autoantibodies have been observed in SARS-CoV-2 infection. Herein, we evaluate the presence of rheumatic, thyroid and phospholipid autoantibodies in sera samples from 120 adult hospitalized patients with COVID-19 in comparison to pre-pandemic samples from 100 healthy individuals. In addition, to estimate the frequency of these autoantibodies in COVID-19, a meta-analysis of selected articles was conducted. Hospitalized patients with COVID-19 had latent autoimmunity characterized by a high frequency of anti-thyroid peroxidase antibodies, rheumatoid factor (RF), anti-cyclic citrullinated peptide third generation antibodies, antinuclear antibodies (ANAs), IgM anti-β2-glycoprotein I (β2GP1) and IgM anti-cardiolipin antibodies. The meta-analysis confirmed our results, with RF and ANAs being the most common autoantibodies. In addition, cluster analysis revealed that those patients with high frequency of RF, IgM anti-β2GP1 antibodies and ANAs had a longer hospital stay, required more vasopressors during hospitalization, and were more likely to develop critical disease. These data suggest that latent autoimmunity influences the severity of COVID-19, and support further post-COVID studies in order to evaluate the development of overt autoimmunity.

Shedding of soluble glycoprotein VI is neither affected by animal-derived antibeta-2-glycoprotein 1 antibodies nor IgG fractions from patients with systemic lupus erythematosus.

: Antibeta-2-glycoprotein 1 (antiβ2GP1) antibodies are associated with increased risk of thrombosis in patients with systemic lupus erythematosus (SLE). The specific effect(s) of antiβ2GP1 antibodies on platelets are unclear. Platelet activation in response to antiplatelet antibodies has been shown to induce shedding of the ectodomain of the platelet collagen receptor, glycoprotein VI (GPVI), releasing soluble GPVI (sGPVI). The aim of this study was to therefore determine whether antiβ2GP1 antibodies, and/or purified IgG fractions, from patients with SLE shed sGPVI from platelets. We determined sGPVI levels in platelet poor plasma from SLE patients with/without antiβ2GP1 antibodies (n = 37), as well as in platelet-rich plasma from healthy donors treated with either SLE-derived IgG fractions containing antiβ2GP1, animal-derived antiβ2GP1, or isotype control antibodies. Levels of sGPVI were higher in three SLE-derived platelet poor plasma with antiβ2GP1 antibodies (103.52 ± 12.32 ng/ml) compared with those without (28.11 ± 12.73 ng/ml). Neither SLE-derived IgG fractions containing antiβ2GP1 antibodies, nor animal-derived antiβ2GP1 antibodies induced significant shedding of sGPVI from healthy donor platelets compared with isotype controls. These results suggest that antiβ2GP1 antibodies do not affect shedding of sGPVI, and therefore collagen-mediated platelet signalling pathways. The shedding activity in SLE patients may be due to factors other than antiβ2GP1 antibodies, for example, metalloproteinases.

Diagnostic biologique du syndrome des antiphospholipides

According to Sapporo criteria revised by the Sydney conference, antiphospholipid syndrome (APS) is defined by the association of thromboembolic or obstetrical events with biological markers. These biological markers are lupus anticoagulant, anti-cardiolipin antibodies and anti-β2Gp1 antibodies. The main issue of APS remains the assessment of the clinical risk. Clinical scores have been developed but they are rarely used in clinical practice. Biological tests such as thrombin generation assay or anti-domain 1 of β2Gp1 antibodies seem to be promising. This review describes the biological diagnosis APS and discussed prediction of potential prediction tools for the prediction of clinical thromboembolic events.

The IgA Isotype of Anti-β2 Glycoprotein I Antibodies Recognizes Epitopes in Domains 3, 4, and 5 That Are Located in a Lateral Zone of the Molecule (L-Shaped).

Background: Antiphospholipid syndrome (APS) is characterized by thrombosis and/or pregnancy morbidity with presence of anti-phospholipid antibodies (aPL). The APS classification criteria only consider the aPL of IgG/IgM isotype, however testing of aPL of IgA isotype is recommended when APS is suspected and consensus aPL are negative. IgA anti-βeta-2 glycoprotein-I (B2GP1) has been clearly related with occurrence of thrombotic events. Antibodies anti-B2GP1 of IgG/M isotypes recognize an epitope in Domain 1 (R39-G43), the epitopes that recognize IgA anti-B2GP1 antibodies are not well-identified.Aim: To determine the zones of B2GP1 recognized by antibodies of IgA isotype from patients with APS symptomatology and positive for IgA anti-B2GP1.Methods: IgA antibodies to Domain-1(D1) and Domain-4/5(D4/5) of B2GP1 (ELISA) and epitope mapping on oligopeptide arrays of B2GP1 were evaluated in sera from a group of 93 patients with at least one thrombotic and with isolated positivity for IgA anti-B2GP1 antibodies (negative for other aPL).Results: A total of 47 patients (50.5%) were positive for anti-D4/5 and 23(25%) were positive for anti-D1. When peptide arrays were analyzed, three zones of B2GP1 reactivity were identified for more than 50% of patients. The center of these zones corresponds to amino acids 140(D3), 204(D4), and 264(D5). The peptides recognized on D3 and D4 contain amino acid sequences sharing high homology with proteins of microorganism that were previously related with a possible APS infectious etiology. In the three-dimensional structure of B2GP1, the three peptides, as the R39-G43 epitope, are located on the right side of the molecule (L-shape). The left side (J-shape) does not bind the antibodies.Conclusions: Patients with thrombotic APS clinical-criteria, and isolated IgA anti-B2GP1 positivity appear to preferentially bind, not to the D1 or D4/5 domains of B2GP1, but rather to three sites in D3, D4, and D5. The sites on D3 and D4 were previously described as the target identified by human monoclonal antibodies derived from patients that were capable of inducing APS in animal models. The localization of these epitopes opens a new route to explore to increase understanding of the patholophysiology of the APS and to propose new alternatives and therapeutic targets.

Prevalence and Significance of Non-conventional Antiphospholipid Antibodies in Patients With Clinical APS Criteria.

Background: The biological diagnostics of antiphospholipid syndrome (APS) takes into account the persistent positivity for anticardiolipin and/or anti-β2GP1 antibodies and/or presence of lupus anticoagulant (LA). However, some non-conventional antiphospholipid antibodies have emerged that could help in the diagnosis of APS.Objectives: To study the potential usefulness of non-conventional antiphospholipid antibodies in clinical practice.Methods: Eighty-seven patients, aged from 15 to 92 years were included and classified in following groups: 41 patients positive for the conventional antibodies with clinical criterion of APS (31 with primary APS and 10 secondary), 17 seronegative APS (SNAPS) patients (i.e., persistent negativity for the conventional antibodies with a strong clinical suspicion of APS), 11 asymptomatic antiphospholipid antibodies carriers (i.e., persistent positivity for the conventional antibodies without clinical evidence of APS), and 18 patients presenting with a first thrombotic or obstetrical event. IgG and IgM were detected to the following antigens: phosphatidylserine/prothrombin (PS/PT) by ELISA, and phosphatidic acid, phosphatidyl-ethanolamine, phosphatidyl-glycerol, phosphatidyl-inositol, phosphatidylserine, annexin V, prothrombin by immunodot. Anti-β2GP1 IgA, and anti-β2GP1 domain 1 IgG were detected by chemiluminescence.Results: Positivity for the non-conventional antibodies was correlated with APS severity; patients with catastrophic APS (CAPS) being positive for 10.7 (Median, Range: 5–14) non-conventional antibodies. 9/17 seronegative patients were positive for at least one of non-conventional antibodies. A study of non-supervised hierarchical clustering of all markers revealed that anti-PS/PT antibodies showed high correlation with the presence of LA. All patients with APS triple positivity (highest risk profile) exhibited also persistent positivity for anti-PS/PT antibodies.Conclusions: Our data obtained from a prospective cohort constituted mainly by patients with primary APS, suggest that non-conventional APS antibodies may be useful for patients classified as SNAPS. They demonstrate the potential value of aPS/PT antibodies as a strong marker of APS. We propose that anti-PS/PT antibodies could be a surrogate APS biological marker of LA to classify in high-risk profile patients treated by direct oral anticoagulants (DOACs), in whom LA detection cannot be achieved.

P42: Detective value of anti‐cardiolipin antibodies and anti‐β2GP1 antibodies subtypes in serum of infertile women

American Journal of Reproductive ImmunologyVolume 80, Issue S1 p. 76-76 ABSTRACTS P42: Detective value of anti-cardiolipin antibodies and anti-β2GP1 antibodies subtypes in serum of infertile women First published: 26 June 2018 https://doi.org/10.1111/aji.41_12984Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume80, IssueS1Special Issue: American-Sino Joint Meeting of Reproductive Immunology (ASRI-CSI 2018), June 28-1 July, 2018 Shanghai, ChinaJune 2018Pages 76-76 RelatedInformation

Are Anti-β2 Glycoprotein 1 Antibodies Associated with Placenta-Mediated Pregnancy Complications? A Nested Case-Control Study.

While anti-β2 glycoprotein 1 (anti-β2GP1) antibody positivity is included in the diagnostic criteria for antiphospholipid syndrome (APS), the association between anti-β2GP1 and the obstetrical complications of APS has been inconsistently reported and remains unclear. We completed a case-control study nested within the Canadian Ottawa and Kingston (OaK) Birth Cohort to evaluate the association between anti-β2GP1 antibody positivity and placenta-mediated pregnancy complications. Five hundred cases were randomly selected among pregnant women who experienced any of the following independently adjudicated placenta-mediated pregnancy complications: preeclampsia, placental abruption, late pregnancy loss (≥ 12 weeks' gestation), and birth of a small-for-gestational age (SGA) infant < 10th percentile. Five hundred pregnant women without any placenta-mediated pregnancy complications were selected as controls. Stored blood samples were analyzed for the presence of anti-β2GP1 antibodies by enzyme-linked immunosorbent assay. Anti-β2GP1 immunoglobulin G (IgG) and/or immunoglobulin M (IgM) antibodies in titers ≥ 20 G/M units (> 99th percentile) were present in 24 of 497 (4.8%) of controls and 33 of 503 (6.6%) of cases. There was no significant difference between cases and controls for the composite outcome of any placenta-mediated pregnancy complications (odds ratio, 1.38, 95% confidence interval [CI], 0.8-2.37, p = 0.25). Our results call into question the association between anti-β2GP1 antibodies and placenta-mediated pregnancy complications, with further research needed.