Genetic Factors in Antiphospholipid Syndrome: Preliminary Experience with Whole Exome Sequencing.

As in many autoimmune diseases, the pathogenesis of the antiphospholipid syndrome (APS) is the result of a complex interplay between predisposing genes and triggering environmental factors, leading to a loss of self-tolerance and immune-mediated tissue damage. While the first genetic studies in APS focused primarily on the human leukocytes antigen system (HLA) region, more recent data highlighted the role of other genes in APS susceptibility, including those involved in the immune response and in the hemostatic process. In order to join this intriguing debate, we analyzed the single-nucleotide polymorphisms (SNPs) derived from the whole exome sequencing (WES) of two siblings affected by APS and compared our findings with the available literature. We identified genes encoding proteins involved in the hemostatic process, the immune response, and the phospholipid metabolism (PLA2G6, HSPG2, BCL3, ZFAT, ATP2B2, CRTC3, and ADCY3) of potential interest when debating the pathogenesis of the syndrome. The study of the selected SNPs in a larger cohort of APS patients and the integration of WES results with the network-based approaches will help decipher the genetic risk factors involved in the diverse clinical features of APS.

Impaired B cell anergy is not sufficient to breach tolerance to nuclear antigen in Vκ8/3H9 lupus-prone mice.

BACKGROUND: Systemic lupus erythematosus (SLE) is a severe autoimmune disease in which immune tolerance defects drive production of pathogenic anti-nuclear autoantibodies. Anergic B cells are considered a potential source of these autoantibodies due to their autoreactivity and overrepresentation in SLE patients. Studies of lupus-prone mice have shown that genetic defects mediating autoimmunity can breach B cell anergy, but how this breach occurs with regards to endogenous nuclear antigen remains unclear. We investigated whether B and T cell defects in congenic mice (c1) derived from the lupus-prone New Zealand Black strain can breach tolerance to nuclear self-antigen in the presence of knock-in genes (Vκ8/3H9; dKI) that generate a ssDNA-reactive, anergic B cell population. METHODS: Flow cytometry was used to assess splenic B and T cells from 8-month-old c1 dKI mice and serum autoantibodies were measured by ELISA. dKI B cells stimulated in vitro with anti-IgM were assessed for proliferation and activation by examining CFSE decay and CD86. Cytokine-producing T cells were identified by flow cytometry following culture of dKI splenocytes with PMA and ionomycin. dKI B cells from 6-8-week-old mice were adoptively transferred into 4-month-old wild type recipients and assessed after 7 days via flow cytometry and immunofluorescence microscopy. RESULTS: c1 dKI mice exhibited B cell proliferation indicative of impaired anergy, but had attenuated autoantibodies and germinal centres compared to wild type littermates. This attenuation appeared to stem from a decrease in PD-1hi T helper cells in the dKI strains, as c1 dKI B cells were recruited to germinal centres when adoptively transferred into c1 wild type mice. CONCLUSION: Anergic, DNA-specific autoreactive B cells only seem to drive profound autoimmunity in the presence of concomitant defects in the T cell subsets that support high-affinity plasma cell production.

Independent association of low IFNλ1 gene expression and type I IFN score/IFNλ1 ratio with obstetric manifestations and triple antiphospholipid antibody positivity in primary antiphospholipid syndrome.

Recent data suggest an important role of type I interferons (IFN) in antiphospholipid syndrome (APS). Here we aimed to evaluate the interplay of type I and type III (or IFNλs) IFNs in APS and potential clinical and serological associations. Our findings suggest that patients with primary APS (PAPS) and systemic lupus erythematosus (SLE)/APS displayed increased type I IFN scores but decreased IFNλ1 gene expression levels compared to healthy individuals, as assessed with real-time qPCR analysis in isolated peripheral blood mononuclear cells (PBMCs). Type I IFN score/IFNλ1 ratio was remarkably higher in patients with PAPS and SLE/APS as well as in SLE patients with or without antiphospholipid antibodies (aPL) vs controls. In conclusion, our results reveal an association between low IFNλ1 expression and obstetric APS. Moreover, the type I IFN score/IFNλ1 ratio seems to be a potential marker of high risk APS given its associations with triple aPL positivity.

Relationship of Antiphospholipid Antibodies to Risk of Dementia: A Systematic Review.

Antiphospholipid antibodies (aPL) are well-known risk factors for venous and arterial thrombosis, but their association with cognitive dysfunction has not been widely investigated in the general population and in patients with primary and secondary antiphospholipid syndrome (APS). We performed a systematic review searching MEDLINE via PubMed and Cochrane (CENTRAL) databases for observational studies reporting on the association between aPL and dementia in the general population, in subjects carrying aPL, in patients with cognitive disorder/dementia, and in primary and secondary APS. Prevalence of anticardiolipin (aCL) IgG ranged from 5.9% to 31.1% in the general population, with aCL titers being more elevated in subjects with functional decline of cognitive functions or with neurological alterations as detected by imaging. The prevalence of aPL ranged from 6.0 to 56.6% in patients with vascular dementia. Regarding patients with primary and secondary APS, a severe cognitive deficit has been described in up to 60% of patients, 33.3% of systemic lupus erythematosus (SLE)-APS and 22.2% of SLE patients without aPL. Five studies included patients with primary APS with divergent results, while 18 studies investigated the association between aPL and cognitive impairment in patients with SLE. Of these, 14 reported a positive association between aPL, mostly aCL and LAC, and cognitive impairment while little evidence on anti ß2-Glycoprotein I exists. Mechanisms leading to cognitive dysfunction are not well characterized and may include vascular aPL-induced micro and macro-thrombosis and immune-mediated neuronal toxicity pathways in the cerebral district.

Pathogenesis of antiphospholipid syndrome: recent insights and emerging concepts.

Introduction: Even though our understanding of the antiphospholipid syndrome (APS) has improved tremendously over the last decades, we are still not in a position to replace symptomatic anticoagulation by pathogenesis based causal treatments. Areas covered: Recent years have provided further insights into pathogenetically relevant mechanisms. These include a differentiation of pathogenic subtypes of antiphospholipid antibodies (aPL), novel mechanisms modulating disease activity, for example, extracellular vesicles and microRNA, and novel players in pathogenesis, for example, neutrophils and neutrophil extracellular traps (NETs). Expert commentary: It is evident that aPL induce a proinflammatory and procoagulant state and recent data suggest that different aPL species activate different signaling pathways which sometimes converge into a common cellular response. This implies that presence of more than one aPL species may disproportionally increase the risk for the major manifestations of APS, that is, thrombosis and fetal loss. Further delineation of the pathogenic mechanisms will hopefully provide clues to causal rather than symptomatic treatments of APS.

Investigation of follicular helper T cells, as a novel player, in preeclampsia.

Preeclampsia (PE) is characterized by hypertension and proteinuria. It occurs in an around 3% to 5% of all pregnancies worldwide. The fetus is kind of semiallograft to the maternal host; immune system components encounter fetal antigens and develop adverse immune responses. Recently, it has been observed that the immune system plays an important role in PE. In the current study, we have tried to investigate the role of follicular helper T (Tfh) cells in the pathogenesis of PE. Blood samples of 49 PE women and 50 healthy controls were collected. Peripheral blood mononuclear cells were isolated, cells were cultured, and then RNA was extracted. Autoantibody and secretory cytokine levels were analyzed by ELISA. Tfh frequency and transcription levels of the related molecules and cytokine were assessed by flow cytometry and real-time PCR, respectively. The frequency of circulating Tfh cell in PE women was significantly higher compared with the healthy pregnant woman (Tfh cells with CD4+ ICOS + , P = 0.0064 and Tfh cells with CD4 + CXCR5 + , P = 0.029). Moreover, mRNA expression levels of CXCR5, BCL6, IL-21, and IL-6 ( P = 0.0006, P = 0.008, P = 0.0063, and P = 0.027, respectively) were upregulated in PE patients. Furthermore, IL-6 ( P = 0.0014) and IL-21 ( P = 0.0059) levels in both group were assayed and the results showed increased in patient group. We also measured autoantibody levels including antiphospholipid antibodies ( P = 0.0001), anticardiolipin antibodies ( P = 0.0004), anti-TPO ( P = 0.0008), anti-TG ( P = 0.001) in circulation of PE group, which were higher than the control group. This study provided insights into the involvement of Tfh cells in etiology and pathogenesis of PE, probably by developing autoantibodies.

Anti-phospholipid syndrome in seven leprosy patients with thrombotic events on corticosteroid and/or thalidomide regimen: insights on genetic and laboratory profiles.

INTRODUCTION: Corticosteroids and/or thalidomides have been associated with thromboembolism events (TBE) in multibacillary (MB) leprosy. This report aimed to determine genetic and laboratory profiles associated with leprosy and TBE. METHODS: Antiphospholipid antibodies (aPL), coagulation-related exams, prothrombin and Leiden's factor V mutations, and ß2-glycoprotein-I (ß2GPI) Val247Leu polymorphism were assessed. RESULTS: Six out of seven patients with leprosy were treated with prednisone and/or thalidomide during TBE and presented at least one positive aPL. All patients presented ß2GPI polymorphism, and one showed prothrombin mutation. CONCLUSIONS: Corticosteroid or thalidomide adverse effects and aPL and ß2GPI polymorphisms may cause TBE in patients with MB leprosy.

Anti-phospholipid syndrome in seven leprosy patients with thrombotic events on corticosteroid and/or thalidomide regimen: insights on genetic and laboratory profiles

Abstract INTRODUCTION Corticosteroids and/or thalidomides have been associated with thromboembolism events (TBE) in multibacillary (MB) leprosy. This report aimed to determine genetic and laboratory profiles associated with leprosy and TBE. METHODS Antiphospholipid antibodies (aPL), coagulation-related exams, prothrombin and Leiden's factor V mutations, and ß2-glycoprotein-I (ß2GPI) Val247Leu polymorphism were assessed. RESULTS Six out of seven patients with leprosy were treated with prednisone and/or thalidomide during TBE and presented at least one positive aPL. All patients presented ß2GPI polymorphism, and one showed prothrombin mutation. CONCLUSIONS Corticosteroid or thalidomide adverse effects and aPL and ß2GPI polymorphisms may cause TBE in patients with MB leprosy.

Antiphospholipid antibodies enhance rat neonatal cardiomyocyte apoptosis in an in vitro hypoxia/reoxygenation injury model via p38 MAPK.

A significant amount of myocardial damage during a myocardial infarction (MI) occurs during the reperfusion stage, termed ischaemia/reperfusion (I/R) injury, and accounts for up to 50% of total infarcted tissue post-MI. During the reperfusion phase, a complex interplay of multiple pathways and mechanisms is activated, which ultimately leads to cell death, primarily through apoptosis. There is some evidence from a lupus mouse model that lupus IgG, specifically the antiphospholipid (aPL) antibody subset, is pathogenic in mesenteric I/R injury. Furthermore, it has previously been shown that the immunodominant epitope for the majority of circulating pathogenic aPLs resides in the N-terminal domain I (DI) of beta-2 glycoprotein I (ß2GPI). This study describes the enhanced pathogenic effect of purified IgG derived from patients with lupus and/or the antiphospholipid syndrome in a cardiomyocyte H/R in vitro model. Furthermore, we have demonstrated a pathogenic role for aPL containing samples, mediated via aPL-ß2GPI interactions, resulting in activation of the pro-apoptotic p38 MAPK pathway. This was shown to be inhibited using a recombinant human peptide of domain I of ß2GPI in the fluid phase, suggesting that the pathogenic anti-ß2GPI antibodies in this in vitro model target this domain.

Antiphospholipid Antibodies and Infertility: A Gene Expression Study in Decidual Stromal Cells.

BACKGROUND: Antiphospholipid antibodies (aPL) have been advocated as potential mediators of unexplained female infertility, but no evidence has yet been raised to support such an association. OBJECTIVES: To test the hypothesis that aPL might interfere with uterine decidualization, a gene expression study was performed on decidual stromal cells treated with different aPL preparations. METHODS: Decidual stromal cells were isolated from first-trimester deciduas obtained from two women undergoing elective abortion, and treated with: (i) a ß2GPI-dependent aPL monoclonal antibody (IS3); (ii) IS3 plus TIFI, a synthetic peptide mimicking PL-binding region of ß2GPI; and (iii) IgG from healthy subjects (NHS). Gene expression data were acquired using human HT-12 v3 beadchip arrays (Illumina). Differential expression analysis was performed by fitting a gene-wise linear model using the treatment group and decidual source as covariates. RESULTS: In the comparison of IS3 versus IgG NHS-treated decidual cells, gene ontology (GO) enrichment was expressed in terms relating to well-characterized aPL-mediated cellular effects: "inflammatory response," "immune response," "response to stress," "oxydoreductase activity," "metalloendopeptidase activity," and "cytokine/chemokine activity." As expected, almost all genes were up-regulated by IS3 treatment. The same GO categories appeared to be differentially expressed when IS3 treatment was compared to IS3 + TIFI, but with most genes being down-regulated. CONCLUSIONS: Given the inflammatory response evinced on gene expression analysis of decidual stromal cells treated with a ß2GPI -dependent aPL monoclonal antibody, it is feasible that aPL might interfere with uterine decidualization, affecting the early stages of implantation and ultimately resulting in female infertility.

The haplotype M2 of the ANXA5 gene is not associated with antitrophoblast antibodies.

PURPOSE: The M2 haplotype in ANXA5 as well as antitrophoblast antibodies predispose to recurrent pregnancy loss (RPL). Since M2/ANXA5 can be a factor for development of antiphospholipid antibodies (aPL), this study aimed to trace a possible association of M2 with antitrophoblast antibodies. METHODS: One hundred patients with two or more consecutive, idiopathic RPLs were divided in two subgroups, JEG-3(+) (n = 42) and JEG-3(-) (n = 58), according to the anti-JEG-3 reactivity measured in subjects' sera. Both subgroups were genotyped for ANXA5 promoter haplotypes and genetic frequencies were compared to available fertile and control populations, as well as within the subgroups. RESULTS: M2/ANXA5 was generally enriched in the JEG-3 screened cohort of RPL patients in comparison to fertile and population controls. Despite the relatively higher abundance of the haplotype in the JEG-3(-) sample as compared to JEG-3(+) patients and in the JEG-3(-) primary RPL subset in particular, compared to the rest of patients, there was no statistically significant difference between both, JEG-3(-) and JEG-3(+) subgroups. CONCLUSION: It appears that the haplotype M2/ANXA5 is not associated with the presence of anti-trophoblast antibodies. Our finding indicates that anti-trophoblast antibodies are a class of molecules that differ from aPL and from anti-b2-GPI antibodies, apparently not directed to same or similar epitopes that aPL and anti-b2-GPI would recognize.

Beta2-glycoprotein I gene polymorphisms Val247Leu and Trp316Ser in Spanish patients with primary antiphospholipid syndrome.

The significance of beta2-glycoprotein I (ß2GPI) polymorphisms in the production of anti-ß2GPI and other antiphospholipid autoantibodies (aPL) and in the pathogenesis of primary antiphospholipid syndrome (PAPS) is not well understood. We performed a study comparing the distribution of polymorphisms at codons 247 (Val247Leu) and 316 (Trp316Ser) of the ß2GPI gene in a Caucasian Spanish population of PAPS patients and healthy controls, and then making correlations with the development of anti-ß2GPI antibodies and other aPL and associated clinical manifestations. A total of 57 PAPS patients and 100 control subjects were included. In the analysis of Val247Leu polymorphism, alleles (V and L) and genotypes (V/V, V/L, L/L) were similarly distributed in PAPS patients and controls (P = 0.66 and P = 0.22, respectively). Regarding Trp316Ser polymorphism, we found a higher percentage of patients with respect to controls expressing S allele (11.4 vs. 5%, P = 0.02) and T/S genotype (22.8 vs. 10%, P = 0.02). However, when we compared T/T and T/S genotypes in PAPS patients, we found no differences regarding generation of anti-ß2GPI, other aPL and clinical manifestations favoring any genotype. Our findings suggest that among Spanish Caucasians, polymorphisms at codon 247 (Val247Leu) do not seem to influence PAPS pathogenesis. On the contrary, polymorphisms at codon 316 (Trp316Ser), by means of an increased S allele and T/S genotype presence in Spanish Caucasian patients, might play a role in the pathogenic development of PAPS, although mechanism would not involve an increased production of anti-ß2GPI and other aPL.

Structural and functional characterization of a human IgG monoclonal antiphospholipid antibody.

Antiphospholipid antibodies (aPL) are likely involved in the pathogenesis of the antiphospholipid syndrome (APS). This study analyzes the structural and functional characteristics of a human monoclonal aPL (HL7G) from the IgG2 subtype with λ light chains generated from a patient with primary APS and recurrent cerebral microemboli. DNA encoding the variable region of heavy and light chains of the antibody was sequenced, analyzed, and compared to HL5B a previously described monoclonal aPL from the same patient. Both antibodies are derived from the same germline genes. HL7G had similar but more extensive somatic mutations in the CDR1 and 2 regions than HL5B, indicating that both antibodies are closely related and derived by a T cell-dependent antigen driven process. In ELISA assays HL7G bound to cardiolipin and several other phospholipid antigens in the absence of protein cofactors. Different from HL5B this aPL bound to ß2-glycoprotein I (ß2GPII). This suggests that reactivity of aPL against ß2GPI is determined by only few specific amino acid exchanges. HL7G was able to induce tissue factor (TF) as one of the procoagulant effects of aPL. Our data suggest that the binding specificity of aPL is only of limited value to predict the biological effect and the pathophysiological impact of the antibodies.

Anti-phospholipid human monoclonal antibodies inhibit CCR5-tropic HIV-1 and induce beta-chemokines.

Traditional antibody-mediated neutralization of HIV-1 infection is thought to result from the binding of antibodies to virions, thus preventing virus entry. However, antibodies that broadly neutralize HIV-1 are rare and are not induced by current vaccines. We report that four human anti-phospholipid monoclonal antibodies (mAbs) (PGN632, P1, IS4, and CL1) inhibit HIV-1 CCR5-tropic (R5) primary isolate infection of peripheral blood mononuclear cells (PBMCs) with 80% inhibitory concentrations of <0.02 to approximately 10 microg/ml. Anti-phospholipid mAbs inhibited PBMC HIV-1 infection in vitro by mechanisms involving binding to monocytes and triggering the release of MIP-1alpha and MIP-1beta. The release of these beta-chemokines explains both the specificity for R5 HIV-1 and the activity of these mAbs in PBMC cultures containing both primary lymphocytes and monocytes.

Use of monoclonal antibodies to dissect specificity and pathogenesis of antiphospholipid antibodies.

Monoclonal antiphospholipid antibodies (aPL) have been utilized to dissect the relationship between their sequence, structure, binding and biological properties relevant to the pathogenesis of the antiphospholipid syndrome. In particular, sequence analysis of aPL has highlighted the clustering of certain amino acid residues in the antigen contact sites of their heavy and light chains. Therefore, these sequence motifs are likely to be important in determining aPL binding properties and their pathogenic effects. Experiments, however, using monoclonal aPL engineered to contain specific point mutations in their sequence which alter their ability to bind relevant antigens have shown that these alterations in binding are not directly mirrored by their pathogenic effects. In this review we focus on work carried out by others and ourselves using monoclonal antibodies with specific binding properties to extend our knowledge of the non-linear structure-binding-function relationship of aPL.

Endocytic sequestration of the B cell antigen receptor and toll-like receptor 9 in anergic cells.

In autoimmune prone murine strains, sequential engagement of the B cell antigen receptor (BCR) on the cell surface and toll-like receptors (TLRs) in late endosomes is necessary and sufficient for secretion of autoantibodies. However, ubiquitous nucleoprotein self-antigens fail to elicit productive TLR activation, and break self-tolerance in anergic DNA-reactive B cells. The mechanisms limiting TLR activation in these cells are largely unknown. Here, we demonstrate that in anergic 3H9/Vkappa8 and Ars/A1 B cells the normal endocytic transit of both the ligated BCR and TLR9 into late endosomes is abrogated. The BCR and TLR9 arrest together just outside late endosomes, indicating that they enter this compartment along a single, regulated endocytic route. Access to late endosomes could be restored by reversing anergy through several methods, including conferring genetic susceptibility to autoimmunity, complementing proximal BCR signaling or by preventing BCR binding to self-antigen. Downstream of the BCR, JNK, which is activated in naive but not anergic B cells, regulated entry into late endosomes. Restoration of BCR and TLR9 endocytic trafficking rescued TLR9 activation by BCR-captured ligands. These results indicate that B cell anergy is reinforced by the exclusion of both TLRs and their BCR captured ligands from subcellular environments necessary for TLR activation.

[Beta2-glycoprotein I polymorphism].

Antiphopholipid syndrome (APS) is a major cause of ischemic stroke in young adults. In our study, stroke patients with antiphospholipid antibodies (APL) were significantly younger and were more likely to be women than stroke patients without APL. Valvular heart disease, neurological complications, and hematological disorders were more frequent in the APL-positive group. The mean value of thrombin-antithrombin III complex was significantly lower in the APL-positive group. beta2-Glyoprotein I (beta2-GPI) is the antigen primarily responsible for APL. At the DNA level, 4 different types of allelic polymorphisms have been detected in beta2-GPI. The allele at position 247 has codes for either valine (V) or leucine (L), which results in genotypic expression of VV, VL, or LL. In our study, the V and VL genotypes were more frequent in patients with cerebral infarction than in normal controls. The VL genotype was more frequent among patients aged less than 60 years than in those aged more than 60 years. The mean values of beta-thromboglobulin and platelet factor 4 in patients with the VL genotype were significantly higher than those with the LL genotype. The results suggested that V247 beta2-GPI allele is one of the genetic risk factors for the development of cerebral infarction through platelet activation.

Recurrent pregnancy loss and frequency of eight antiphospholipid antibodies and genetic thrombophilic factors in Czech women.

PROBLEM: The aim of this study was to investigate frequencies of eight antiphospholipid antibodies (aPLs) in serum, four genetic thrombophilic factors and their mutual relation in 206 patients with repeated pregnancy loss (RPL). METHOD OF STUDY: Enzyme-linked immunosorbent assay was used for detection of aPLs against ph-serine, ph-ethanolamine, ph-inositol, DL-glycerol, phosphatidic acid, anti-annexin V, cardiolipin, and beta2-GPI. FV 1691G>A (Leiden mutation), FII 20210G>A mutation, MTHFR 677C>T and MTHFR 1298A>C variant genotypes were determined using a melting curve analysis of the PCR amplification product detected by the fluorescence resonance energy transfer. Genotypic distribution and allelic frequencies were calculated. Correlation between aPLs and thrombophilic factors was tested by chi-square and Fisher exact test. RESULTS: Our results show significantly increased prevalence of aPLs against ph-inositol (17-19.6% dependent on number of spontaneous miscarriages) and against ph-serine (18-25%). aPLs in IgG prevail. In 96% of the studied group, at least one risk factor was found (either aPLs positivity or thrombophilic factor). Both aPLs and thrombophilic factors were present in 43%. In the group of women with three or more RPLs, strong positive correlation of aPLs positivity and thrombophilic risk factors was observed. CONCLUSION: Antiphospholipide antibodies and genetic thrombophilic factors are important risk factors in the pathogenesis of RPL. Both autoantibodies against various kinds of phospholipides and genetic thrombophilic factors must be studied together in diagnosis of RPL for appropriate treatment.

Genetic variation in the paraoxonase-3 (PON3) gene is associated with serum PON1 activity.

Low serum paraoxonase1 (PON1) activity determined by paraoxon substrate is associated with coronary heart disease (CHD), diabetes and systemic lupus erythematosus (SLE) risk. In this investigation, we have examined the role of genetic variation in the PON3 gene in relation to PON1 activity and SLE risk in a biracial sample comprising 377 SLE patients and 482 controls from US whites and blacks. We genotyped six PON3 tagging single nucleotide polymorphisms (tagSNPs) and examined their associations with PON1 activity, SLE risk, antiphopholipid autoantibodies (APA), lupus nephritis, carotid vascular disease, and inflammation. With the exception of PON1 activity, no other significant associations were found with PON3 SNPs. Multiple regression analysis including all six PON3 tagSNPs and PON1/Q192R and L55M SNPs revealed significant association of PON1 activity with 4 SNPs: PON3/A10340C (p < 0.0001), PON3/A2115T (p = 0.002), PON1/L55M (p < 0.0001) and PON1/Q192R (p < 0.0001). These four SNPs explained 2%, 1%, 8% and 19% of the variation in PON1 activity, respectively. In summary, our new data indicate that genetic variation in the PON3 gene influences serum PON1 activity independently of the known effect of PON1 genetic variation. To our knowledge, this is the first study reporting the association of the PON3 gene variants with PON1 activity.