Distinct and overlapping effects of ß2-glycoprotein I conformational variants in ligand interactions and functional assays.

One of the most abundant coagulation proteins is ß2-glycoprotein I (ß2GPI) that is present in humans at a concentration of around 200 mg/L. Its physiological role is only partially understood, but it adopts several different structural forms the majority of which are the open and closed forms. We isolated native (circular) ß2GPI and converted it into an open conformation. The effectiveness of these procedures was assessed by Western blot and negative-staining electron microscopy. We found that in coagulation assays the open form of ß2GPI had a significant prolonging effect on fibrin formation in a dilute prothrombin time test (p < 0.001). In the dilute activated partial thromboplastin time test, both conformations had a significant prolonging effect (p < 0.001) but the open conformation was more effective. In a fluorescent thrombin generation assay both conformations slightly delayed thrombin generation with no significant effect on the quantity of formed thrombin. By using surface plasmon resonance assays, the equilibrium dissociation constants of both the open and closed conformations of ß2GPI showed a similar and strong affinity to isolated anti-ß2GPI autoantibodies (Kd closed ß2GPI = 5.17 × 10-8 M, Kd open ß2GPI = 5.56 × 10-8 M) and the open form had one order of magnitude stronger affinity to heparin (Kd = 0.30 × 10-6 M) compared to the closed conformation (Kd = 3.50 × 10-6 M). The two different forms of ß2GPI have distinct effects in functional tests and in ligand binding, which may considerably affect the intravascular events related to this abundant plasma protein in health and disease.

In silico identification of new inhibitors for ßeta-2-glycoprotein I as a major antigen in antiphospholipid antibody syndrome.

Beta 2 glycoprotein I (ß2GPI) is a major antigen for autoantibodies present in antiphospholipid antibody syndrome (APS). ß2GPI is a single polypeptide with five repeated domains and different conformations. The activated J-shaped conformation of ß2GPI binds to negatively charged phospholipids in the membrane via the fifth domain and causes blood clotting reactions. We applied a drug repurposing strategy using virtual screening and molecular dynamics to find the best FDA drugs against the fifth domain of ß2GPI. In the first phase, FDA drugs that had the most favorable ΔG with the fifth domain of ß2GPI were selected by virtual screening. Among these drugs that had the most favorable ΔG, Vorapaxar and Antrafenine were selected for molecular dynamics (MD) simulation studies. MD simulation was performed to evaluate the stability of Vorapaxar and Antrafenine complexes and the effect of the two drugs on protein conformation. Also, MD simulation was done to investigate the effect of Antrafenine and Vorapaxar on the binding of ß2GPI to the platelet model membrane. According to the results, Vorapaxar and Antrafenine were bound to the protein with the favorable binding energy (Vorapaxar and Antrafenine binding energies are - 49.641 and - 38.803 kcal/mol, respectively). In this study, it was shown that unlike protein alone and protein in the Antrafenine complex, the protein in the Vorapaxar complex was completely separated from the model membrane after 350 ns. Moreover, Vorapaxar led to more changes in the activated J-shape of ß2GPI. Thus, Vorapaxar can be a suitable candidate for further investigations on the treatment of APS.

Insights into the pathogenesis of catastrophic antiphospholipid syndrome. A case report of relapsing catastrophic antiphospholipid syndrome and review of the literature on ischemic colitis.

We present the case of a woman with a severe clinical history of antiphospholipid syndrome and persistent positivity for lupus anticoagulant, IgG anticardiolipin and IgG anti-ß2Glycoprotein I antibodies. An acute clinical onset characterized by severe abdominal pain immediately followed by circulatory shock and histological colonic small vessel thrombosis pattern pointed to a diagnosis of ischemic colitis. The subsequent rapid onset of pulmonary alveolitis and heart failure associated to subendocardial hypoperfusion led to a diagnosis of definite catastrophic antiphospholipid syndrome (CAPS). Conventional triple therapy together with a broad-spectrum preventive antibiotic therapy were quickly initiated, and the outcome was favorable. We evaluated the patients with ischemic colitis in CAPS described in the literature between 1992 and May 2019 and our CAPS case. In accordance with the "two-hit" hypothesis and on the basis of the patients' data, we would like to speculate that the colonic wall necrosis related to ischemic colitis damaged the intestinal barrier causing loss of resistance to bacteria and leading to endotoxemia and bacteremia with bacteria translocation through the circulatory stream to the lungs and heart. The bacteria acted as the priming factor which favored the binding of ß2Glycoprotein I to the endothelium vessels in the colon, lungs, and heart following activation of anti-ß2Glycoprotein I antibodies which attached to the domain I of ß2Glycoprotein I. This was followed by complement activation which triggered the thrombotic and cytokine storm. If further clinical studies confirm this hypothesis, the treatment of CAPS could be more targeted and effective.

Effects of ß2/aß2 on oxLDL-induced CD36 activation in THP-1 macrophages.

AIMS: ß2-glycoprotein I/anti-ß2-glycoprotein I antibody complex (ß2/aß2) could promote oxLDL-induced endothelial inflammation through Toll-like receptor 4 (TLR4), therefore accelerates atherosclerosis in patients with anti-phospholipid syndrome (APS). However, effects of ß2/aß2 and TLR4 on oxLDL-induced CD36 activation in macrophages remain to be elucidated and are currently under investigation. MATERIALS AND METHODS: THP-1 macrophages with or without the pre-treatment of TAK-242, a TLR4 inhibitor, were treated with RPMI 1640, oxLDL, oxLDL+ß2/aß2 or oxLDL + LPS.CD36 expression and subsequent intracellular lipid accumulation, cholesterol-transportation-related proteins (ACAT1, ABCG1 and ABCA1) expression, inflammatory cytokines (IL-1ß, TNF-α and IL-6) secretion, focal adhesion kinases (FAK) activation and matrix metalloproteinases (MMP-2 and MMP-9) expression by these THP-1 macrophages were evaluated. Moreover, effects of TLR4 on oxLDL+ß2/aß2-induced peroxisome proliferators-activated receptor-γ (PPAR-γ) expression and CD36 translocation have also been observed. KEY FINDINGS: Compared with oxLDL-treated ones, CD36 expression, intracellular lipid accumulation and FAK activation were inhibited, whereas the levels of inflammatory cytokines and MMPs were upregulated in THP-1 macrophages treated with oxLDL+ß2/aß2 (p < 0.05). Moreover, observed differences between oxLDL-treated and oxLDL+ß2/aß2-treated THP-1 macrophages could be reversed by TAK-242 pre-treatment (p < 0.05). Furthermore, oxLDL+ß2/aß2 promoted PPAR-γ expression and CD36 cytoplasmic translocation in THP-1 macrophages, these effects could also be attenuated by TAK-242 (p < 0.05). SIGNIFICANCE: Through a TLR4 dependent manner, ß2/aß2 inhibited oxLDL-induced CD36 expression, lipid accumulation and FAK activation, while promoted inflammatory cytokines and MMPs expression in THP-1 macrophages, indicating the novel dual roles played by ß2/aß2 in APS-related atherosclerosis.

Anti-ß2GPI antibodies enhance atherosclerosis in ApoE-deficient mice.

Accelerated atherosclerosis often occurs in patients with antiphospholipid syndrome (APS), and auto-antibodies to ß2 glycoprotein I (anti-ß2GPI) are confirmed as pathogenic antibodies to APS. Our previous studies have demonstrated that the conversion of mouse peritoneal macrophages into foam cells could be enhanced by co-existence of ß2GPI and anti-ß2GPI IgG, but this phenomenon has not been explored in vivo. Here, we present a mouse model to observe the effect of anti-ß2GPI IgG in the development of atherosclerosis. Male ApoE-deficient mice were intraperitoneally injected with anti-ß2GPI IgG (100 µg/mouse) and homologous control IgG (100 µg/mouse) every week for 16 weeks. Plasma lipid composition, magnetic resonance imaging (MRI) and histological staining were used to evaluate vascular inflammation, lumen stenosis and plaque stability. The results showed that the levels of total cholesterol, triglycerol and low-density lipoprotein-cholesterol in plasma were not changed in all mice fed with high-fat diet, but the level of high-density lipoprotein-cholesterol was lower and the atherosclerosis index was significantly increased in HD + anti-ß2GPI group than in other high-fat diet groups. In addition, compared with NR IgG-treated mice, anti-ß2GPI IgG-treated mice showed more lipid deposition in the carotid artery, markedly narrowed arteriolar lumen as well as higher MMP-9 expression, more macrophages and fewer collagen fibers in the aortic arch root. Furthermore, the aortic mRNA levels of TNF-α, IL-1ß, and MCP-1 were significantly increased in anti-ß2GPI IgG-treated mice. Together, these data indicate that anti-ß2GPI IgG increases vascular inflammation, aggravates atherosclerosis and promotes the formation of vulnerable plaque in ApoE-deficient mice.

Catastrophic antiphospholipid syndrome: Lessons from 14 cases successfully treated in a single center. A narrative report.

The study aimed to evaluate the clinical significance of laboratory findings in patients with catastrophic antiphospholipid syndrome (CAPS) and to report the effects of a well-defined treatment protocol in 14 consecutive cases. Thirteen patients (12 presenting one and one presenting two episodes of CAPS) were consecutively treated and monitored between 1986 and 2017. Antiphospholipid antibody (aPL) characteristics of the patients were compared with those of 64 matched controls (45 antiphospholipid syndrome patients and 19 aPL carriers) who did not develop CAPS during the same mean follow-up period (12 years ±â€¯9.9 SD). Triple aPL positivity (IgG/IgM anticardiolipin + IgG/IgM anti-ß2Glycoprotein I + lupus anticoagulants) significantly prevailed in the CAPS patients with respect to the controls (p = 0.003). IgG anticardiolipin and IgG anti-ß2Glycoprotein I mean antibody titers of the CAPS patients were significantly higher than those of the controls (p = 0.0018 and p = 0.003, respectively). Triple therapy (anticoagulation + plasma exchange + steroids) was administered to all the CAPS cases except for one. Beginning in 2009, intravenous immunoglobulin infusion has also been included in the triple therapy protocol (six patients). All the patients recovered from CAPS; five showed renal failure and one a I-II class New York Heart Association (NYHA) dilated cardiomyopathy. Long-term outcomes of CAPS included a gradual worsening of renal failure in one patient who required hemodialysis 30 years after the acute episode. Renal function improved in the other four patients. The patient affected with dilated cardiomyopathy worsened to a II class NYHA over a five year period. Currently all the patients are alive. A specific antiphospholipid antibody profile could be considered a risk factor associated to CAPS. Early use of a defined treatment protocol based on triple therapy either or not associated with IVIG was associated with recovery in all CAPS patients.

Anti-ß2GPI/ß2GPI induces neutrophil extracellular traps formation to promote thrombogenesis via the TLR4/MyD88/MAPKs axis activation.

Antiphospholipid antibodies (aPLs) are a large group of heterogeneous antibodies that bind to anionic phospholipids alone or in combination with phospholipid binding proteins. Increasing evidence has converged to indicate that aPLs especially anti-ß2 glycoprotein I antibody (anti-ß2GPI) correlate with stroke severity and outcome. Though studies have shown that aPLs promote thrombus formation in a neutrophil-dependent way, the underlying mechanisms remain largely unknown. In the present study, we investigated the effect of anti-ß2GPI in complex with ß2GPI (anti-ß2GPI/ß2GPI) on neutrophil extracellular traps (NETs) formation and thrombus generation in vitro and in vivo. We found that anti-ß2GPI/ß2GPI immune complex induced NETs formation in a time- and concentration-dependent manner. This effect was mediated by its interaction with TLR4 and the production of ROS. We demonstrated that MyD88-IRAKs-MAPKs, an intracellular signaling pathway, was involved in anti-ß2GPI/ß2GPI-induced NETs formation. We also presented evidence that tissue factor was expressed on anti-ß2GPI/ß2GPI-induced NETs, and NETs could promote platelet aggregation in vitro. In addition, we identified that anti-ß2GPI/ß2GPI-induced NETs enhanced thrombus formation in vivo, and this effect was counteracted by using DNase I. Our data suggest that anti-ß2GPI/ß2GPI induces NETs formation to promote thrombogenesis via the TLR4/MyD88/MAPKs axis activation, and could be a potentially novel target for aPLs related ischemic stroke.

Further Investigations of the Effects of Anti-ß2GP1 Antibodies on Collagen-Induced Platelet Aggregation.

Anti-beta-2-glycoprotein 1 (anti-ß2GP1) antibodies are associated with increased thrombotic risk in patients with autoimmune disease. There is conflicting evidence on the effects of anti-ß2GP1 antibodies on platelets, with both enhanced and inhibited aggregation previously reported. However, previous studies did not include isotype antibodies to ensure the observed effects were due to anti-ß2GP1 antibodies. The aims of this study were to (1) investigate the effects of anti-ß2GP1 antibodies on collagen-induced platelet aggregation in parallel with negative control (buffer normal saline) and isotype control antibodies and (2) determine the lupus anticoagulant (LA) activity of anti-ß2GP1 antibodies used. Three animal-derived anti-human-ß2GP1 antibodies (1.25, 2.5, and 5 µg/mL) incubated with healthy platelet-rich plasma were activated by collagen (2.5 µg/mL). Each anti-ß2GP1 antibody demonstrated the inhibition of aggregation compared to negative control, but not to isotype control. No anti-ß2GP1 antibody demonstrated LA activity, suggesting they were probably nonpathological. This study highlights both negative and isotype control markers are important to validate the effects of anti-ß2GP1 antibodies. Assays to measure anti-domain I-ß2GP1 antibodies are recommended to be used in conjunction with functional measures to further investigate the effects of anti-ß2GP1 antibodies.

Reversible drug-induced antiphospholipid syndrome.

We report an original case of reversible antiphospholipid syndrome (APS) due to minocycline in a young male patient who experienced recurrent strokes while taking minocycline. He started minocycline therapy (50 mg twice daily) at 15 years old for acne. After three years of treatment, the patient experienced a lateral medullary syndrome. He was treated with aspirin while minocycline was continued. Eighteen months later, the patient complained about horizontal binocular diplopia. MRI revealed an infarct of the oculomotor nerve nucleus. Laboratory investigations revealed high titers of anti-beta 2 glycoprotein 1 (antiß2GP1) antibodies of 470 U/ml (normal range <15 U/ml) and antiphosphatidylethanolamine antibodies of 137.4 U/ml (normal range <18 U/ml). Other laboratory tests were normal. Six weeks after discontinuation of minocycline, anti-ß2GP1 antibodies decreased to 335 U/ml and to 36 U/ml at six months and then remained negative for six years. Many drugs have been considered as possibly causing APS but only in a limited number of patients. To our knowledge this is the first case of drug-induced APS with complete disappearance of high titers of anti-ß2GP1 antibodies after minocycline withdrawal. This case also illustrates the need to monitor the levels of antiphospholipid antibodies, even though initial values are high and confirmed after 12 weeks.

Plasmodium berghei EXP-1 interacts with host Apolipoprotein H during Plasmodium liver-stage development.

The first, obligatory replication phase of malaria parasite infections is characterized by rapid expansion and differentiation of single parasites in liver cells, resulting in the formation and release of thousands of invasive merozoites into the bloodstream. Hepatic Plasmodium development occurs inside a specialized membranous compartment termed the parasitophorous vacuole (PV). Here, we show that, during the parasite's hepatic replication, the C-terminal region of the parasitic PV membrane protein exported protein 1 (EXP-1) binds to host Apolipoprotein H (ApoH) and that this molecular interaction plays a pivotal role for successful Plasmodium liver-stage development. Expression of a truncated EXP-1 protein, missing the specific ApoH interaction site, or down-regulation of ApoH expression in either hepatic cells or mouse livers by RNA interference resulted in impaired intrahepatic development. Furthermore, infection of mice with sporozoites expressing a truncated version of EXP-1 resulted in both a significant reduction of liver burden and delayed blood-stage patency, leading to a disease outcome different from that generally induced by infection with wild-type parasites. This study identifies a host-parasite protein interaction during the hepatic stage of infection by Plasmodium parasites. The identification of such vital interactions may hold potential toward the development of novel malaria prevention strategies.

Antiphospholipid syndrome: analysis of dilute Russell's viper venom time titer.

To evaluate the characteristic features of the dilute Russell's viper venom time (DRVVT) titer in the antiphospholipid syndrome (APS). The medical record of 3660 consecutive patients with DRVVT orders between 2006 and 2015 were examined for criteria satisfying the diagnosis of APS. DRVVT titer was studied as a function of titer distribution, titer stability, and clinicopathologic features. Twenty-six patients were diagnosed with APS based on a persistently positive DRVVT and a history of arterial or venous thrombosis. DRVVT titer was mostly of low magnitude (65-77% of patients), was of similar value between initial and repeat testing (mean DRVVT titer 1.40 vs. 1.38; P = 0.858; mean time interval 216 days), and was positively associated with anticardiolipin antibodies (IgG and IgM) and antibeta-2-glycoprotein I antibodies (IgG and IgM) (P < 0.020). Low titer and moderate/high titer DRVVT were associated with a triple positive antiphospholipid antibody profile in 0 and 62% of patients, respectively (P < 0.020). DRVVT titer in APS was predominantly low in magnitude, stable over time, and associated with specific antiphospholipid antibody profiles.

Validation of a New Panel of Automated Chemiluminescence Assays for Anticardiolipin Antibodies in the Screening for Antiphospholipid Syndrome.

BACKGROUND: Antibodies anticardiolipin (aCL) and anti-ß2-glycoprotein I (aß2GPI) are two of three laboratory criteria of antiphospholipid syndrome (APS). All of assays of antiphospholipid antibodies (aPL), coagulation assays as well as ELISAs, show methodological shortcomings, that affect their sensitivity and specificity. Therefore, we decided to validate these parameters for a new chemiluminescent examination (CLIA). METHODS: aCL and aß2GPI antibodies were measured by ELISAs (AIDA, Bad Kreuznach, Germany) and aß2GPI with CLIA kits (Werfen, Barcelona, Spain). RESULTS: When we evaluated both assays, the coefficient of variation for CLIA was slightly lower (9.04 - 12.74%) than for ELISA (11.05 - 15.3%) and the LOD was 0.2 U/L. The dilution series showed significant linearity for all CLIA methods, aCL IgG, aCL IgM, aß2GPI IgG, and aß2GPI IgM (0 - 3000 U/L), and method comparison studies revealed good agreement with the currently used ELISA (Kappa values ranging 0.534 - 0.936) without determination of aß2GPI IgG. The determination aß2GPI IgG by CLIA method shows higher positivity in 31 samples. These new aCL IgG, aCL IgM, aß2GPI IgG, and aß2GPI IgM tests have excellent analytical characteristics and allow fully automated and simultaneous analysis on an analyzer. CONCLUSIONS: Chemiluminescent determination of an automated analyzer can improve the fundamental parameters of tests such as reproducibility between laboratories.

Antiphospholipid antibody-mediated effects in an arterial model of thrombosis are dependent on Toll-like receptor 4.

Patients with antiphospholipid syndrome (APS) produce antiphospholipid antibodies (aPL) and develop vascular thrombosis that may occur in large or small vessels in the arterial or venous beds. On the other hand, many individuals produce aPL and yet never develop thrombotic events. Toll-like receptor 4 (TLR4) appears to be necessary for aPL-mediated prothrombotic effects in venous and microvascular models of thrombosis, but its role in arterial thrombosis has not been studied. Here, we propose that aPL alone are insufficient to cause thrombotic events in an arterial model of APS, and that a concomitant trigger of innate immunity (e.g. TLR4 activation) is required. We show specifically that anti-ß2-glycoprotein I (anti-ß2GPI) antibodies, a subset of aPL, accelerated thrombus formation in C57BL/6 wild-type, but not TLR4-deficient, mice in a ferric chloride-induced carotid artery injury model. These aPL bound to arterial and venous endothelial cells, particularly in the presence of ß2GPI, and to human TLR4 by enzyme-linked immunoassay. Arterial endothelium from aPL-treated mice had enhanced leukocyte adhesion, compared to control IgG-treated mice. In addition, aPL treatment of mice enhanced expression of tissue factor (TF) in leukocytes induced by the TLR4 ligand lipopolysaccharide (LPS). aPL also enhanced LPS-induced TF expression in human leukocytes in vitro. Our findings support a mechanism in which aPL enhance TF expression by leukocytes, as well as augment adhesion of leukocytes to the arterial endothelium. The activation of TLR4 in aPL-positive individuals may be required to trigger thrombotic events.

The Pathogenicity of Anti-ß2GP1-IgG Autoantibodies Depends on Fc Glycosylation.

To analyze the glycosylation of anti-ß2GP1, we investigated purified IgG from healthy children, patients with APS, and asymptomatic adult carriers of antiphospholipid antibodies. We observed that in the sera of healthy children and of patients with APS, IgG3 and IgG2 were predominant, respectively. The potentially protective anti-ß2GP1-IgM was lower in the sera of healthy children. Although anti-ß2GP1-associated C1q did not differ between children and patients with antiphospholipid syndrome, the associated C3c was significantly higher in the sera of healthy children. This indicates a more efficient clearance of anti-ß2GP1 immune complexes in the healthy children. This clearance is not accompanied by inflammation or coagulatory events. It is likely that the most important pathogenic factor of the anti-ß2GP1-IgG is related to the different glycosylation observed in healthy and diseased individuals. We detected a significantly higher sialylation of anti-ß2GP1-IgG isolated from the sera of healthy children and asymptomatic adults when compared with that of patients with clinically apparent antiphospholipid syndrome. Low sialylated IgG reportedly ameliorates inflammation and inflammation promotes hyposialylation. Thus, both reactions create a vicious circle that precipitates the pathology of the antiphospholipid syndrome including thrombus-formation. We conclude that the increased sialylation of anti-ß2GP1-IgG of sera of healthy individuals limits their pathogenicity.

Detection of IgG anti-Domain I beta2 Glycoprotein I antibodies by chemiluminescence immunoassay in primary antiphospholipid syndrome.

BACKGROUND: IgG anti-Domain I (anti-DI) ß2 Glycoprotein I (ß2GPI) antibodies are associated to thrombotic risk in antiphospholipid syndrome (APS), but their detection is technically difficult. In this study, a chemiluminescent immunoassay (CLIA) was used to evaluate the clinical significance of IgG anti-DI in a large cohort of patients with primary APS (PAPS). METHODS: The study population included 88 patients with PAPS, 63 ELISA-negative subjects and 166 controls. IgG anti-DI, IgG anticardiolipin (aCL) and IgG anti-ß2GPI antibodies were assayed using CLIA (HemosIL AcuStar®). RESULTS: The sensitivity and specificity of IgG anti-DI antibodies were comparable to those of IgG aCL and IgG anti-ß2GPI antibodies. There was a significant agreement, association and titre correlation between IgG anti-DI and IgG aCL as well as IgG anti-ß2GPI antibodies (p<0.001 for all). IgG anti-DI antibody showed lesser prevalence and mean titres in the pregnancy morbidity than in thrombotic and PAPS patients with both involvements (p<0.001). Regarding the conventional aPL antibody profiles, the triple positivity group had higher prevalence and mean titres than single and double positivity ones (p<0.001). CONCLUSIONS: This study provides further evidence that anti-DI antibodies can be considered a promising biomarker for risk assessment particularly in patients having vascular thrombosis and triple conventional aPL positivity.

Aspirin-triggered lipoxin prevents antiphospholipid antibody effects on human trophoblast migration and endothelial cell interactions.

OBJECTIVE: Antiphospholipid antibodies (aPL) interfere with several physiologic functions of human trophoblasts, including reducing their ability to migrate, decreasing their production of angiogenic factors, and inducing an inflammatory response. This may provide the underlying mechanism by which aPL responses lead to recurrent pregnancy loss or preeclampsia in women with obstetric antiphospholipid syndrome (APS). Although treatment with heparin may reduce the rate of recurrent pregnancy loss, the risk of preeclampsia remains high. Therefore, alternative treatments are needed for the management of pregnant patients with APS. Since aspirin-triggered lipoxins (ATLs) have immune and angiogenic modulatory properties, the objective of this study was to determine the effects of the ATL 15-epi-lipoxin A4 on the function of aPL-altered human trophoblasts in the first trimester of pregnancy. METHODS: A first-trimester human trophoblast cell line (HTR8) was treated with mouse anti-human ß2 -glycoprotein I monoclonal antibodies (aPL) in the presence or absence of the ATL 15-epi-lipoxin A4 . Trophoblast migration and interactions with endometrial endothelial cells were measured using Transwell and coculture assays. Trophoblast secretion of cytokines and angiogenic factors was measured by enzyme-linked immunosorbent assay. RESULTS: Treatment of HTR8 cells with ATL reversed the aPL-induced decrease in trophoblast migration, an effect that appeared to be regulated through restoration of interleukin-6 production. Using a model of spiral artery transformation, aPL and sera from APS patients with pregnancy morbidity disrupted trophoblast-endothelial cell interactions, and treatment with ATL restored the stability of the cocultures. In contrast, ATL treatment did not resolve the proinflammatory and antiangiogenic responses of trophoblasts induced by aPL. CONCLUSION: These findings indicate that ATLs may have some benefits in terms of preventing the effects of aPL on trophoblast function, which raises the possibility of the use of ATLs as an adjuvant therapy in women with aPL.

An A1-A1 mutant with improved binding and inhibition of ß2GPI/antibody complexes in antiphospholipid syndrome.

ß2 glycoprotein I (ß2GPI) is the most common antigen for autoimmune antibodies in antiphospholipid syndrome (APS). Thrombosis is a clinical feature of APS. We created a molecule (A1-A1) that consists of two identical ß2GPI-binding modules from ApoE receptor 2 (ApoER2). A1-A1 binds to ß2GPI/antibody complexes, preventing their association with ApoER2 and anionic phospholipids, and reducing thrombus size in the mouse model of APS. Here, we describe a mutant of A1-A1 (mA1-A1ND) with improved affinity for ß2GPI. mA1-A1ND inhibits the binding of ß2GPI to cardiolipin in the presence of anti-ß2GPI antibodies, and inhibits the binding to phospholipids in plasma samples of APS patients, affecting the clotting time. Reduction of the clotting time demonstrates the presence of soluble ß2GPI/antibody complexes in patients' plasma. These complexes either already exist in patients' plasma or form rapidly in the proximity to phospholipids. All members of the low-density lipoprotein receptor family bind ß2GPI. Modeling studies of A1 in a complex with domain V of ß2GPI (ß2GPI-DV) revealed two possible modes of interaction of a ligand-binding module from lipoprotein receptors with ß2GPI-DV. In both orientations, the ligand-binding module interferes with binding of ß2GPI to anionic phospholipids; however, it interacts with two different but overlapping sets of lysine residues in ß2GPI-DV, depending on the orientation.

Isolated IgA anti- ß2 glycoprotein I antibodies in patients with clinical criteria for antiphospholipid syndrome.

Seronegative antiphospholipid syndrome (SNAPS) is an autoimmune disease present in patients with clinical manifestations highly suggestive of Antiphospholipid Syndrome (APS) but with persistently negative consensus antiphospholipid antibodies (a-PL). IgA anti-ß 2 Glycoprotein I (aB2-GPI) antibodies are associated with APS. However, they are not currently considered to be laboratory criteria due to the heterogeneity of published works and the use of poor standardized diagnostic systems. We have aimed to assess aPL antibodies in a group of patients with clinical manifestations of APS (C-APS) to evaluate the importance of the presence of IgA aB2GPI antibodies in APS and its relation with other aPL antibodies. Only 14% of patients with C-APS were positive for any consensus antibody, whereas the presence of isolated IgA aB2GPI antibodies was found in 22% of C-APS patients. In patients with arterial thrombosis IgA aB2GPI, antibodies were the only aPL antibodies present. Serologic profile in primary APS (PAPS) is different from systemic autoimmune disorders associated APS (SAD-APS). IgA aB2GPI antibodies are more prevalent in PAPS and IgG aB2GPI antibodies are predominant in SAD-APS. The analysis of IgA aB2GPI antibodies in patients with clinical manifestations of PAPS might avoid underdiagnosed patients and provide a better diagnosis in patients with SAD-APS. Laboratory consensus criteria might consider including analysis of IgA aB2GPI for APS diagnosis.

Novel antiphospholipid antibodies in autoimmune bullous diseases.

BACKGROUND: Pemphigus and bullous pemphigoid are two autoimmune diseases that have similar pathogenesis. Both have a genetic predisposition, which promotes the production of auto antibodies targeted against different components of the epidermal desmosome and hemidesmosome. Antiphospholipid antibodies (aPL) are heterogeneous group of antibodies found in patients with autoimmune diseases and inflammatory conditions and are associated with thrombotic events. OBJECTIVE: We sought to determine the expression profile of eight non classical aPLs in ABD patients. METHODS: A cohort of 266 serum samples of patients with pemphigus, bullous pemphigoid and controls was screened for the presence of eight aPL antibodies, using the Bio-Rad BioPlex™ 2200 system. RESULTS: Phosphatidylserine-beta-2-glycoprotein-I (aPS-ß2GPI) and anti prothrombin complex (aPT-PT) serum profiles were significantly more prevalent among ABD patients; 20.7% patients with ABD compared to 5.9% of control patients were positive for aPS-ß2GPI IgM. In addition, aPT-PT IgM was more prevalent among ABD patients (31% vs. 14.8%). CONCLUSION: aPL auto antibodies are more prevalent in ABD. Any clinical association should be further determined.

[Inhibitory effects of fluvastatin on activation of THP-1 cells induced by anti-beta2GPI/beta2GPI complex].

This study is to explore the interventional effects of fluvastatin on anti-beta2GPI/beta2GPI-induced activation in THP-1 mononuclear cells. In vitro, human mononuclear cells THP-1 were treated with fluvastatin, LPS and anti-beta2GPI/beta2GPI, then the TF expression on THP-1 cells was detected by real-time quantitative PCR (RT-qPCR) or TF activity was detected by kit. TNF-alpha mRNA and its protein expression were investigated by RT-PCR and ELISA kit. The expression of phospho-NF-kappaB p65 and inhibitory protein of NF-kappaB (IkappaB-alpha) were measured by Western blotting. The results suggested that the expression of TF and TNF-alpha on THP-1 cells was significantly up-regulated with treatment of anti-beta2GPI/beta2GPI complex (100 mg x L(-1)), compared with that of untreated cells (P < 0.05). Fluvastatin (50 mg x L(-1)) could decrease TF (mRNA and activity) expression and the level of TNF-alpha (mRNA and protein) in THP-1 cells with anti-beta2GPI/beta2GPI complex. The expression of TF and TNF-alpha was shown in a concentration-dependent manner. Moreover, anti-beta2GPI/beta2GPI complex could downregulate IkappaB-alpha levels and increase the levels of phospho-NF-kappaB p65. And these effects of anti-beta2GPI/beta2GPI complex could be blocked by fluvastatin. In conclusion, fluvastatin may interfere the expression and regulation of NF-kappaB signal transduction pathway, thereby inhibit the effects of anti-beta2GPI/beta2GPI on activation of THP-1 cells, by decreasing the expression of TF and TNF-alpha.