Antiphospholipid syndrome: 30 years and our contribution

The complement system and human autoimmune diseases

Genetic deficiencies of early components of the classical complement activation pathway (especially C1q, r, s, and C4) are the strongest monogenic causal factors for the prototypic autoimmune disease systemic lupus erythematosus (SLE), but their prevalence is extremely rare. In contrast, isotype genetic deficiency of C4A and acquired deficiency of C1q by autoantibodies are frequent among patients with SLE. Here we review the genetic basis of complement deficiencies in autoimmune disease, discuss the complex genetic diversity seen in complement C4 and its association with autoimmune disease, provide guidance as to when clinicians should suspect and test for complement deficiencies, and outline the current understanding of the mechanisms relating complement deficiencies to autoimmunity. We focus primarily on SLE, as the role of complement in SLE is well-established, but will also discuss other informative diseases such as inflammatory arthritis and myositis.

Hydroxychloroquine in obstetric antiphospholipid syndrome: rationale and results of an observational study of refractory cases

BACKGROUND

The current recommended therapy of obstetric antiphospholipid syndrome (APS) is a long-term anticoagulant therapy that affects the final event, namely, when the thrombosis has already occurred. Unfortunately, this schedule is not always effective and fails despite the correct risk stratification and an adequate adjusted dose.

MATERIALS AND METHODS

From 2013 to 2020 we observed 217 women with antiphospholipid antibodies and obstetric morbidities who were treated with conventional treatment protocol (aspirin low doses ± LMWH). Among them 150 (69.1%) successfully completed pregnancy with delivery and live birth on the background of LMWH and aspirin therapy and in 67 (30.9%) women despite a traditional therapy regimen, obstetric complications were noted. Later, 56 of these 67 women became pregnant again and were offered traditional therapy plus hydroxychloroquine. Fifteen women refused HCQ treatment due to possible potential side effects. The final cohort consisted of 41 women with positive antiphospholipid antibodies and obstetric and thrombotic complications who received LMWH, aspirin low doses and HCQ at a dose of 200-400mg per day from the beginning of pregnancy.

RESULTS

Forty-one aPL women treated with HCQ after failed previous anticoagulant therapy had live births in 32 cases (78%). Adding of HCQ to the combination of LMWH and LDA showed good overall obstetric results and increased the number of live births in another 32 women. So, a total of 182 (83.8%) of initial 217 aPL-women ended their pregnancies with live birth after adding the HCQ to the traditional therapy with LMWH and low doses of aspirin.

CONCLUSION

In 20-30% of cases the live birth despite anticoagulation cannot be achieved. Perhaps APS is not just anticoagulation. The study of pathophysiological mechanisms suggests that some patients will benefit from other therapy (in addition to anticoagulant). Therapy that affects the early effects of aPL on target cells (monocytes, endothelial cells, etc.) or before binding to receptors-this therapy will be preferable and potentially less harmful than the officially accepted one to date. From this point of view, HCQ looks promising and can be used as an alternative candidate for women with refractory obstetric antiphospholipid syndrome. Adding HCQ should be considered in some selected patients with failed pregnancy after treatment with anticoagulants.

Periodic bilayer organization in the complexes of Beta-2 Glycoprotein I with anionic lipid membranes

β2 glycoprotein I (β2GPI) is a soluble protein that participates in blood coagulation, clearance of apoptotic bodies and generation of antigens in antiphospholipid syndrome among many other functions. We studied the aggregates formed by β2GPI with the anionic phospholipids palmitoyloleoylphosphatidyl glycerol, dimyristoylphosphatidyl glycerol, dipalmitoylphosphatidyl glycerol and cardiolipin using small angle X-ray scattering. The complexes obtained in a medium containing 0.01 M NaCl showed Bragg peaks up to the sixth order in a well-defined integer sequence indicating the presence of a lamellar stacking with a periodicity of 17.8 nm and with largely reduced membrane fluctuations. Modeling the complex signal allowed us to conclude that the coherence length was only two bilayers and that about 15% of the total surface was actually stacked. The space between bilayers allows accommodating an extended β2GPI molecule making a bridge between the interacting bilayers. The interactions between membranes mediated by β2GPI was favored when the membranes were in the liquid crystalline state.

Systematic review of observational studies reporting antiphospholipid antibodies in patients with solid tumors

This review summarizes the evidence on antiphospholipid (aPL) antibodies and related thromboembolic events in patients with solid tumors. Data sources included Medline, EMBASE, Web of Science, PubMed ePubs, and the Cochrane Central Register of Controlled Trials through August 2019 without restrictions. Observational studies that evaluated patients with solid tumors for the presence of aPL antibodies were included. Data were extracted and quality was assessed by one reviewer and cross-checked by another. Thirty-three studies were identified. Gastrointestinal (GI) and genitourinary (GU) cancers were the most frequently reported. Compared with healthy patients, patients with GI cancer were more likely to develop anticardiolipin antibodies (risk ratio [RR], 5.1; 95% confidence interval [CI], 2.6-9.95), as were those with GU (RR, 7.3; 95% CI, 3.3-16.2) and lung cancer (RR, 5.2; 95% CI, 1.3-20.6). The increased risk for anti-β2-glycoprotein I or lupus anticoagulant was not statistically significant. Patients with lung cancer who had positive aPL antibodies had higher risk of developing thromboembolic events than those who had negative antibodies (RR, 3.8%; 95% CI, 1.2-12.2), while the increased risk in patients with GU cancer was not statistically significant. Deaths due to thromboembolic events were more common among patients with lung cancer who had elevated aPL antibodies. A limitation of this review is that the results are contingent on the reported information. We found an increased risk of developing aPL antibodies in patients with GI, GU, and lung cancers resulting in thromboembolic events and death. Further studies are needed to better understand the pathogenesis and development of aPL antibodies in cancer.

Exosome-Contained APOH Associated With Antiphospholipid Syndrome

Background

Antiphospholipid syndrome (APS) is a systemic autoimmune disease that can lead to thrombosis and/or pregnancy complications. Exosomes, membrane-encapsulated vesicles that are released into the extracellular environment by many types of cells, can carry signals to recipient cells to affect angiogenesis, apoptosis, and inflammation. There is increasing evidence suggesting that exosomes play critical roles in pregnancy. However, the contribution of exosomes to APS is still unknown.

Methods

Peripheral plasma was collected from healthy early pregnancy patients (NC-exos) and early pregnancy patients with APS (APS-exos) for exosome extraction and characterization. The effect of exosomes from different sources on pregnancy outcomes was determined by establishing a mouse pregnancy model. Following the coincubation of exosomes and human umbilical vein endothelial cells (HUVECs), functional tests examined the features of APS-exos. The APS-exos and NC-exos were analyzed by quantitative proteomics of whole protein tandem mass tag (TMT) markers to explore the different compositions and identify key proteins. After incubation with HUVECs, functional tests investigated the characteristics of key exosomal proteins. Western blot analysis was used to identify the key pathways.

Results

In the mouse model, APS-exos caused an APS-like birth outcome. In vitro experiments showed that APS-exos inhibited the migration and tube formation of HUVECs. Quantitative proteomics analysis identified 27 upregulated proteins and 9 downregulated proteins in APS-exos versus NC-exos. We hypothesized that apolipoprotein H (APOH) may be a core protein, and the analysis of clinical samples was consistent with finding from the proteomic TMT analysis. APOH-exos led to APS-like birth outcomes. APOH-exos directly enter HUVECs and may play a role through the phospho-extracellular signal-regulated kinase pathway.

Conclusions

Our study suggests that both APS-exos and APOH-exos impair vascular development and lead to pregnancy complications. APOH-exos may be key actors in the pathogenesis of APS. This study provides new insights into the pathogenesis of APS and potential new targets for therapeutic intervention.

Platelet-activating factor and antiphospholipid antibodies in recurrent implantation failure

Recurrent implantation failure (RIF) refers to cases in which women have had the failure of the embryo implantation after several in vitro fertilization (IVF). The success rate for IVF depends on many different factors. Implantation is a complex step in a successful pregnancy. Antiphospholipid antibodies (aPLs) and platelet-activating factor (PAF) can be considered as effective factors in the embryo implantation. The first purpose of this study is to compare the levels of aPLs and PAF among RIF and fertile control women. The second purpose is evaluating correlations between the blood levels of these factors in this two groups. The levels of twelve types of aPL and PAF in peripheral blood samples of RIF and fertile control women were checked with ELISA method. The results showed that levels of Anti Cardiolipin antibody IgG was above the normal level in 3% of RIF patients. This study examined for the first time the correlation between twelve types of aPLs and PAF in RIF and fertile women. The results of these correlations show that the serum levels of aPLs affects themselves and the serum levels of PAF. The correlation of aPLs levels and PAF levels was different in the two groups. Differences in the correlations of aPLs levels and PAF levels in two groups show that the equal changes in the level of variables examined can have different effects in RIF and the fertile control groups. It is suggested that the correlation between these variables be evaluated in other studies.

Ophthalmologic manifestations in primary antiphospholipid syndrome patients: A cross-sectional analysis of a primary antiphospholipid syndrome cohort (APS-Rio) and systematic review of the literature

OBJECTIVE

There is a broad spectrum of eye involvement in antiphospholipid syndrome (APS). The majority of descriptions are presented as case reports that include mostly APS patients secondary to systemic lupus erythematosus (SLE), with no compelling evidence in primary APS (PAPS). This study aimed to describe ocular manifestations in our well-defined PAPS cohort (APS-Rio) and then perform a systematic literature review (SLR) of ocular manifestations in patients with APS or positivity to aPL without SLE.

METHODS

We retrospectively analyzed PAPS patients followed at our outpatient clinics. All patients fulfilled Sydney APS classification criteria (2006). We evaluated them for ocular symptoms and previous ocular diagnoses. Antiphospholipid antibodies and clinical APS manifestations were compared between patients with and without ocular manifestations. For the SLR, electronic databases were searched up to November 2019.

RESULTS

We studied 105 PAPS patients; 90.5% were female and 56.2% were Caucasian. We found ocular manifestations in 37.1% of our cohort. Thrombosis was the main criteria manifestation (95.2%) and lupus anticoagulant was the most prevalent antibody. Ophthalmologic diagnoses were present in 7 patients, with 5 having retinal vessels thromboses. Amaurosis fugax was the leading complaint, present in 30 patients. In the univariate analysis, amaurosis fugax was related to livedo (p = 0.005), Raynaud's phenomenon (p = 0.048) and the presence of anticardiolipin antibody (≥40 GPL/MPL) (p = 0.041). Hemianopia was associated with arterial hypertension (p = 0.049). In the multivariate analysis, the only association found was between livedo and amaurosis fugax (OR 4.09, 95%CI 1.5-11.11, p = 0.006). Our SLR incorporated 96 articles of ocular manifestations in patients with PAPS or positivity to aPL without SLE. Ocular findings varied from 5 to 88%, including anterior and posterior segments, orbital and neuro-ophthalmologic changes.

CONCLUSION

There is little evidence on ocular manifestations in PAPS. We described an association between livedo and amaurosis fugax. Prospective studies are needed to promote the best treatment and avoid blindness in PAPS patients.

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

Beta 2 glycoprotein I (β2GPI) is a major antigen for autoantibodies present in antiphospholipid antibody syndrome (APS). β2GPI is a single polypeptide with five repeated domains and different conformations. The activated J-shaped conformation of β2GPI 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 β2GPI. In the first phase, FDA drugs that had the most favorable ΔG with the fifth domain of β2GPI 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 β2GPI 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 β2GPI. Thus, Vorapaxar can be a suitable candidate for further investigations on the treatment of APS.

Opposite Profiles of Complement in Antiphospholipid Syndrome (APS) and Systemic Lupus Erythematosus (SLE) Among Patients With Antiphospholipid Antibodies (aPL)

APS is the association of antiphospholipid antibodies (aPL) with thromboses and/or recurrent pregnancy loss (RPL). Among patients with SLE, one-third have aPL and 10–15% have a manifestation of secondary APS. Animal studies suggested that complement activation plays an important role in the pathogenesis of thrombosis and pregnancy loss in APS. We performed a cross-sectional study on complement proteins and genes in 525 patients with aPL. Among them, 237 experienced thromboses and 293 had SLE; 111 had both SLE and thromboses, and 106 had neither SLE nor thrombosis. Complement protein levels were determined by radial immunodiffusion for C4, C3 and factor H; and by functional ELISA for mannan binding lectin (MBL). Total C4, C4A and C4B gene copy numbers (GCN) were measured by TaqMan-based realtime PCR. Two to six copies of C4 genes are frequently present in a diploid genome, and each copy may code for an acidic C4A or a basic C4B protein. We observed significantly (a) higher protein levels of total C4, C4A, C4B, C3, and anticardiolipin (ACLA) IgG, (b) increased frequencies of lupus anticoagulant and males, and (c) decreased levels of complement factor H, MBL and ACLA-IgM among patients with thrombosis than those without thrombosis (N = 288). We also observed significantly lower GCNs of total C4 and C4A among aPL-positive patients with both SLE and thrombosis than others. By contrast, aPL-positive subjects with SLE had significantly reduced protein levels of C3, total C4, C4A, C4B and ACLA-IgG, and higher frequency of females than those without SLE. Patients with thrombosis but without SLE (N = 126), and patients with SLE but without thrombosis (N = 182) had the greatest differences in mean protein levels of C3 (p = 2.6 × 10⁻⁶), C4 (p = 2.2 × 10⁻⁹) and ACLA-IgG (p = 1.2 × 10⁻⁵). RPL occurred in 23.7% of female patients and thrombotic SLE patients had the highest frequency of RPL (41.0%; p = 3.8 × 10⁻¹⁰). Compared with non-RPL females, RPL had significantly higher frequency of thrombosis and elevated C4 protein levels. Female patients with homozygous C4A deficiency all experienced RPL (p = 0.0001) but the opposite was true for patients with homozygous C4B deficiency (p = 0.017). These results provide new insights and biomarkers for diagnosis and management of APS and SLE.

The Solitary Blue Toe: A Unique Presentation of Antiphospholipid Syndrome

Antiphospholipid syndrome is an autoimmune disease characterized by vascular thrombosis involving both the arterial and venous systems that can lead to tissue ischemia or end-organ damage. Much of the literature describes various symptoms at initial presentation, but isolated tissue ischemia manifesting as a solitary blue toe is unusual. We discuss a case of a 23-year-old man who presented to the emergency department with a solitary blue fourth digit with minimal erythema and edema, who was suffering from exquisite pain. Following an extensive workup, the patient was diagnosed with antiphospholipid syndrome with thrombi of the vasculature in their lower extremity. With therapeutic anticoagulation, the patient's symptoms subsided and amputation of the digit was prevented.

Genetics of Hypercoagulable and Hypocoagulable States

Hemostasis is the normal process of blood coagulation in vivo to stop pathologic bleeding. Virchow triad includes venous stasis, hypercoagulability, and vascular injury. Natural anticoagulants include protein C, protein S, and antithrombin. Factor V Leiden is the most common inherited thrombophilia, followed by prothrombin gene mutation. All inherited thrombophilias are passed down in an autosomal dominant fashion. Patients harboring the antiphospholipid antibodies have an increased risk for thrombosis. von Willebrand disease is the most common inherited bleeding disorder; the pattern of inheritance is autosomal. Hemophilia A and B are the only hereditary bleeding disorders inherited in a sex-linked recessive pattern.

[Involvement of thrombophilia in coronary thrombosis]

This review of thrombophilia and coronary thrombosis takes into account the "classical" thrombophilia commonly found in venous pathology and the conditions under which their research may be useful in certain forms of arterial thrombosis especially coronary thrombosis. In addition to the classical thrombophilia, exceptional thrombophilia are evoked, which are both factors of venous thrombosis but also arterial thrombosis. There are also thrombophilia that are more specific to the arterial system such as - homocystein which is potentially both a thrombosis factor but also an agent of arterial parietal lesion or - serotonin which is a factor of arterial spasm and especially coronary spasm. Finally, under the term thrombophilia, it is possible to include thrombophilic conditions, in particular cancers and inflammatory conditions.

Risk of developing antiphospholipid antibodies following viral infection: a systematic review and meta-analysis

Objective The objective of this paper is to conduct a systematic review and meta-analysis on the risk of developing elevated antiphospholipid (aPL) antibodies and related thromboembolic and/or pregnancy events following a viral infection. Method We searched Medline, EMBASE, Web of Science, PubMed ePubs, and Cochrane Central Register of Controlled Trials through June 2016. Independent observational studies of elevated aPL antibodies in patients with a viral infection compared with controls or patients with lupus were included. Results We analyzed 73 publications for 60 studies. Human immunodeficiency virus (HIV) and hepatitis C virus (HCV) were most commonly reported. Compared with healthy controls, patients with HIV were more likely to develop elevated anticardiolipin (aCL) antibodies (risk ratio (RR) 10.5, 95% confidence interval (CI) 5.6-19.4), as were those with HCV (RR 6.3, 95% CI 3.9-10.1), hepatitis B virus (HBV) (RR 4.2, 95% CI 1.8-9.5), and Epstein-Barr virus (EBV) (RR 10.9 95% CI 5.4-22.2). The only statistically significant increased risk for anti-β2-glycoprotein I (anti-β2-GPI) antibodies was observed in patients with HCV (RR 4.8 95% CI 1.0-22.3). Compared with patients with lupus, patients with HIV were more likely to develop elevated aCL antibodies (RR 1.8, 95% CI 1.3-2.6), and those with EBV, elevated anti-β2-GPI antibodies (RR 2.2, 95% CI 1.3-3.9). Thromboembolic events were most prevalent in patients with elevated aPL antibodies who had HCV (9.1%, 95% CI 3.0-18.1), and HBV (5.9%, 95% CI 2.0-11.9) infections, and pregnancy events were most prevalent in those with parvovirus B19 (16.3%, 95% CI 0.78-45.7). However, compared to virus-infected patients with negative aPL antibodies, the only statistically significant increased risk was observed in those with HCV and positive aPL. Conclusions Viral infection can increase the risk of developing elevated aPL antibodies and associated thromboembolic events. Results are contingent on the reported information.

Establishment of a rat model of thrombosis induced by intravenous injection of anti-phosphatidylserine-prothrombin complex antibody

Objective

Recent studies have suggested that aPS-PT antibody is one of the most relevant autoantibodies to APS. This study aimed to demonstrate the pathogenicity of aPS-PT antibody in vivo .

Methods

At first, cultured rat vascular endothelial cells (RECs) were exposed to calf thymus-derived histones. Two hours later, lactate dehydrogenase release from the RECs and expression of PS on the cell surface were assessed. Next, we administered an i.v. injection of calf thymus-derived histones into Wistar rats (12.5 µg/g weight of 8-week-old female rats), and 2 h later they were given an i.v. injection of aPS-PT mAb (1.25 mg/g weight, n = 6) or an equal dose of rat IgM as controls (n = 5). Three days later, histological examination was conducted.

Results

Calf thymus-derived histones (>12.5 µg/ml) could injure RECs in vitro . Simultaneously, annexin V could bind to the RECs; thereby, this result indicated that cell-free histone exposure of vascular endothelial cells induced cell surface expression of PS, which is naturally present inside the plasma membrane. Thrombosis developed with higher frequency in the rats given an i.v. injection of aPS-PT mAb than in controls.

Conclusion

We established a rat model of thrombosis induced by i.v. injection of aPS-PT mAb.

Systematic review of case reports of antiphospholipid syndrome following infection

OBJECTIVE

The objective of this study was to conduct a systematic review of case reports documenting the development of antiphospholipid syndrome or antiphospholipid syndrome-related features after an infection.

METHODS

We searched Medline, EMBASE, Web of Science, PubMed ePubs, and The Cochrane Library - CENTRAL through March 2015 without restrictions. Studies reporting cases of antiphospholipid syndrome or antiphospholipid syndrome-related features following an infection were included.

RESULTS

Two hundred and fifty-nine publications met inclusion criteria, reporting on 293 cases. Three different groups of patients were identified; group 1 included patients who fulfilled the criteria for definitive antiphospholipid syndrome (24.6%), group 2 included patients who developed transient antiphospholipid antibodies with thromboembolic phenomena (43.7%), and group 3 included patients who developed transient antiphospholipid antibodies without thromboembolic events (31.7%). The most common preceding infection was viral (55.6%). In cases that developed thromboembolic events Human immunodeficiency and Hepatitis C viruses were the most frequently reported. Parvovirus B19 was the most common in cases that developed antibodies without thromboembolic events. Hematological manifestations and peripheral thrombosis were the most common clinical manifestations. Positive anticardiolipin antibodies were the most frequent antibodies reported, primarily coexisting IgG and IgM isotypes. Few patients in groups 1 and 2 had persistent antiphospholipid antibodies for more than 6 months. Outcome was variable with some cases reporting persistent antiphospholipid syndrome features and others achieving complete resolution of clinical events.

CONCLUSIONS

Development of antiphospholipid antibodies with all traditional manifestations of antiphospholipid syndrome were observed after variety of infections, most frequently after chronic viral infections with Human immunodeficiency and Hepatitis C. The causal relationship between infection and antiphospholipid syndrome cannot be established, but the possible contribution of various infections in the pathogenesis of antiphospholipid syndrome need further longitudinal and controlled studies to establish the incidence, and better quantify the risk and the outcomes of antiphospholipid-related events after infection.

Synthesis of Phospholipid-Protein Conjugates as New Antigens for Autoimmune Antibodies

Copper(I)-catalyzed azide-alkyne cycloaddition, or CuAAC click chemistry, is an efficient method for bioconjugation aiming at chemical and biological applications. Herein, we demonstrate how the CuAAC method can provide novel phospholipid-protein conjugates with a high potential for the diagnostics and therapy of autoimmune conditions. In doing this, we, for the first time, covalently bind via 1,2,3-triazole linker biologically complementary molecules, namely phosphoethanol amine with human β2-glycoprotein I and prothrombin. The resulting phospholipid-protein conjugates show high binding affinity and specificity for the autoimmune antibodies against autoimmune complexes. Thus, the development of this work might become a milestone in further diagnostics and therapy of autoimmune diseases that involve the production of autoantibodies against the aforementioned phospholipids and proteins, such as antiphospholipid syndrome and systemic lupus erythematosus.