Valine/Leucine247 polymorphism of β2-glycoprotein I in patients with antiphospholipid syndrome: lack of association with anti-β2-glycoprotein I antibodies

An immunogenomic exome landscape of triple positive primary antiphospholipid patients

Primary antiphospholipid syndrome is characterized by thrombosis and autoantibodies directed against phospholipids or associated proteins. The genetic etiology of PAPS remains unknown. We enrolled 21 patients with thromboembolic events associated to lupus anticoagulant, anticardiolipin and anti β2 glycoprotein1 autoantibodies. We performed whole exome sequencing and a systematic variant-based analysis in genes associated with thrombosis, in candidate genes previously associated with APS or inborn errors of immunity. Data were compared to public databases and to a control cohort of 873 non-autoimmune patients. Variants were identified following a state-of-the-art pipeline. Enrichment analysis was performed by comparing with the control cohort. We found an absence of significant HLA bias and genetic heterogeneity in these patients, including when testing combinations of rare variants in genes encoding for proteins involved in thrombosis and of variants in genes linked with inborn errors of immunity. These results provide evidence of genetic heterogeneity in PAPS, even in a homogenous series of triple positive patients. At the individual scale, a combination of variants may participate to the breakdown of B cell tolerance and to the vessel damage.

LDLR and PCSK9 Are Associated with the Presence of Antiphospholipid Antibodies and the Development of Thrombosis in aPLA Carriers

Introduction

The identification of the genetic risk factors that could discriminate non- thrombotic from thrombotic antiphospholipid antibodies (aPLA) carriers will improve prognosis of these patients. Several human studies have shown the presence of aPLAs associated with atherosclerotic plaque, which is a known risk factor for thrombosis. Hence, in order to determine the implication of atherosclerosis in the risk of developing thrombosis in aPLA positive patients, we performed a genetic association study with 3 candidate genes, APOH, LDLR and PCSK9.

Material & Methods

For genetic association study we analyzed 190 aPLA carriers -100 with non-thrombotic events and 90 with thrombotic events- and 557 healthy controls. Analyses were performed by χ2 test and were corrected by false discovery rate. To evaluate the functional implication of the newly established susceptibility loci, we performed expression analyses in 86 aPLA carrier individuals (43 with thrombotic manifestations and 43 without it) and in 45 healthy controls.

Results

Our results revealed significant associations after correction in SNPs located in LDLR gene with aPLA carriers and thrombotic aPLA carriers, when compared with healthy controls. The most significant association in LDLR gene was found between SNP rs129083082 and aPLA carriers in recessive model (adjusted P-value = 2.55 x 10⁻³; OR = 2.18; 95%CI = 1.49–3.21). Furthermore, our work detected significant allelic association after correction between thrombotic aPLA carriers and healthy controls in SNP rs562556 located in PCSK9 gene (adjusted P-value = 1.03 x 10⁻²; OR = 1.60; 95%CI = 1.24–2.06). Expression level study showed significantly decreased expression level of LDLR gene in aPLA carriers (P-value <0.0001; 95%CI 0.16–2.10; SE 0.38–1.27) in comparison to the control group.

Discussion

Our work has identified LDLR gene as a new susceptibility gene associated with the development of thrombosis in aPLA carriers, describing for the first time the deregulation of LDLR expression in individuals with aPLAs. Besides, thrombotic aPLA carriers also showed significant association with PCSK9 gene, a regulator of LDLR plasma levels. These results highlight the importance of atherosclerotic processes in the development of thrombosis in patients with aPLA.

Val/Leu247 polymorphism of β2-glycoprotein I and thrombosis in Chinese patients with SLE

INTRODUCTION

To determine the polymorphism at position 247 of the β2-glycoprotein I (β2GPI) gene in patients with systemic lupus erythematosus (SLE) and healthy controls in the Chinese Han Population and elucidate the relationship between β2GPI polymorphisms and anti-β2GPI levels, and furthermore investigate the correlation between β2GPI polymorphisms and thrombosis in patients with SLE.

METHODS

The β2GPI polymorphisms of 300 patients with SLE and 300 healthy controls were examined by single-specific-primer polymerase chain reaction (SSP-PCR), the efficacy of which was confirmed by sequencing technology. Anti-β2GPI antibodies were tested by enzyme-linked immunosorbent assay. β2GPI polymorphisms associated with thrombosis and the presence of anti-β2GPI antibodies were also statistically evaluated with SPSS software.

RESULTS

The genotype expressions and the allele frequencies were obtained in both patients with SLE and healthy controls. The SLE patients with thrombosis had significantly higher frequencies of the VV genotype and V allele than those without thrombosis and the controls, and there were no differences in VV genotype and V allele expression between the SLE patients without thrombosis and the controls. In contrast, the presence of anti-β2GPI antibody was related to the VV genotype of β2GPI, and the anti-β2GPI-positive patients had obviously higher frequencies of the VV genotype than the negative ones and the controls.

CONCLUSION

The study results suggested that the V/V genotype and the V-encoding allele at position 247 of the β2GPI gene had strong correlation with the occurrence of thrombosis and the production of the anti-β2GPI antibodies, showing that the Val(247) β2GPI allele may be one of the genetic risk factors for the development of thrombosis in patients with SLE.

Risk factors for arterial thrombosis in antiphospholipid syndrome

INTRODUCTION

Antiphospholipid syndrome (APS) is associated with the risk of both arterial and venous thrombosis. However, it is not known which factors might determine the location of thrombosis.

MATERIALS AND METHODS

To retrospectively characterize factors associated with the risk of arterial thrombosis in a cohort of APS patients. Analysis included laboratory and clinical criteria of APS, together with classical cardiovascular risk factors and the possible role of platelet integrin α₂β₁ (807 C/T) and α(IIb)β₃ (PI A1/2) genetic polymorphisms. We enrolled 163 APS patients (123 women and 40 men aged 21-75; mean age 43 years); 78 suffered from arterial thrombosis.

RESULTS

There were no significant differences in the frequency or titers of different antiphospholipid antibodies with the exception of slightly increased frequency of IgG anticardiolipin antibodies (ACL) in the arterial thrombosis group. Livedo reticularis was observed significantly more often in the arterial thrombosis group, particularly in stroke patients. In univariate analysis arterial thrombosis was associated with male gender (OR-2,201; p=0,033), arterial hypertension (OR-2,81; p=0,002) and hypercholesterolemia (OR-3,69; p=0,001). On multivariate analysis arterial hypertension (OR=1,78; p=0,008) and hypercholesterolemia (OR=2,001; p=0,002) remained as independent risk factors for arterial thrombosis. Platelet glycoprotein polymorphisms studied did not show any significant associations with arterial thrombosis in APS patients.

CONCLUSIONS

Among APS patients those with ACL IgG antibodies, having livedo reticularis, and suffering from hypertension an hypercholesterolemia are at the increased risk of arterial thrombosis.

Association between the valine/leucine247 polymorphism of β2-glycoprotein I and susceptibility to anti-phospholipid syndrome: a meta-analysis

Objective: The objective of this paper is to explore whether the valine/leucine247 (Val/Leu247) polymorphism of β2-glycoprotein I (β2GPI) confers susceptibility to anti-phospholipid syndrome (APS) and thrombosis and predicts positivity for anti-β2GPI antibodies. Methods: A meta-analysis was conducted on the associations between the β2GPI Val/Leu247 polymorphism and susceptibility to APS and thrombosis and positivity for anti-β2GPI. Results: A total of 1507 patients with APS and 1450 controls in 12 comparative studies were included in this meta-analysis. Meta-analysis of the β2GPI Val/Leu247 polymorphism showed significant associations between the β2GPI Val allele and APS, thrombosis, and anti-β2GPI positivity (odds ratio (OR) 1.316, 95% confidence interval (CI) 1.068–1.621, p = 0.010; OR 1.908, 95% CI 1.195–3.046, p = 0.007; OR 1.630, 95% CI 1.018–2.609, p = 0.042, respectively). A direct comparison between anti-β2GPI-positive and -negative patients revealed that the frequency of the Val allele was significantly higher in anti-β2GPI-positive patents (OR 1.514, 95% CI 1.017–1.253, p = 0.041). Furthermore, a direct comparison between thrombosis-positive and -negative patients also indicated that the Val/Val + Val/Leu and the Val/Val vs. Leu/Leu genotypes of the β2GPI polymorphism were significantly elevated in patients with thrombosis (OR 2.817, 95% CI 1.200–6.610, p = 0.017; OR 3.312, 95% CI 1.338–8.200, p = 0.010, respectively). Conclusion: This meta-analysis shows that the β2GPI Val/Leu247 polymorphism is associated with susceptibility to APS and thrombosis and with anti-β2GPI positivity.

Val247Leu β2-glycoprotein-I allelic variant is associated with antiphospholipid syndrome: systematic review and meta-analysis

INTRODUCTION

Previous studies have suggested that the possession of the Val/Val genotype of the Val247Leu polymorphism of the β(2)-glycoproteinI (β(2)-GPI) gene may be associated with antiphospholipid syndrome (APS), and, among patients with APS, with the production of anti-β(2)-GPI antibodies or the development of thrombosis. Given the controversial results reported, the aim of this work is to combine previous findings by means of a systematic review and a meta-analysis.

METHODS

We retrieved studies analyzing the genotype of the above-mentioned polymorphism among patients with APS by means of electronic database search. A meta-analysis was conducted in a random effects model and calculations of odds ratio (OR) and confidence intervals (CI) were done. Sensitivity analysis and tests for heterogeneity of the results were performed.

RESULTS

Eight previous studies analyzed the association of APS, anti-β(2)-GPI antibodies and/or thrombosis with the Val247Leu polymorphism. After meta-analysis, patients with APS had a significantly higher prevalence of the Val/Val genotype of this genetic variant when compared with controls (OR=2.04; 95% CI: 1.12, 3.73; P=0.02). Among patients with APS, those with anti-β(2)-GPI antibodies had a higher prevalence of this genotype (OR=1.73; 95% CI: 1.04, 2.87; P=0.03). No significant results were found for the presence of arterial or venous thrombosis.

CONCLUSIONS

Val/Val genotype of β(2)-GPI gene is associated with a significant excess risk to suffer from APS and, among patients with APS, to have anti-β(2)-GPI antibodies. No definite conclusions can be made regarding the association of this polymorphism with thrombosis among APS patients.

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

The significance of beta2-glycoprotein I (β2GPI) polymorphisms in the production of anti-β2GPI 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 β2GPI gene in a Caucasian Spanish population of PAPS patients and healthy controls, and then making correlations with the development of anti-β2GPI 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-β2GPI, 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-β2GPI and other aPL.

Val/Leu247 polymorphism of beta2-glycoprotein I in Brazilian patients with antiphospholipid syndrome--a genetic risk factor?

A genetic polymorphism of the beta2-glycoprotein I (beta2-GPI) is recognized by antiphospholipid antibodies (aPL) and may even play a role in the development of antiphospholipid syndrome (APS). The objectives of this study were to determine a Val/Leu SNP at position 247 of the beta2-GPI gene in Brazilian patients with APS and to compare these data with clinical and laboratory manifestations. Polymorphism assignment was performed by PCR followed by Rsa I restriction endonuclease. The titration of anti-beta2-GPI antibodies was detected by ELISA. The results showed significantly higher frequencies of the V-encoding allele and the homozygous VV genotype in patients with APS than in control subjects (OR = 1.781, P = 0.0068; and OR = 6.413, P < 0.0001, respectively). The frequency of this genotype was also significantly higher in patients with arterial and venous thrombosis than in the control group (52% and 44%, respectively, versus 13%). Anti-beta2-GPI-positive patients had significantly higher frequencies of the VV genotype than the controls subjects (OR = 8.179, P < 0.0001). These results suggest that the V-encoding allele and the homozygous VV genotype at position 247 of the beta2-GPI gene may play a role in the generation of anomalous beta2-GPI, with consequent auto-antibody production, and in phenotype expression of arterial and venous thrombosis in APS patients.

Revised classification criteria for antiphospholipid syndrome and the thrombotic risk in patients with autoimmune diseases

BACKGROUND

The classification criteria for antiphospholipid syndrome (APS) were updated in 2006.

OBJECTIVE

The aim of the study was to analyze associations between clinical complications and laboratory test abnormalities typical for APS in a group of patients with autoimmune diseases, based on the recently updated criteria.

PATIENTS/METHODS

Three hundred and thirty-six patients were enrolled into the study, with the majority (n = 235) suffering from systemic lupus erythematosus. Laboratory determinations included: lupus anticoagulant (LA), anticardiolipin (aCL) and anti-beta(2)-glycoprotein I (anti-beta(2)GPI) antibodies (ABs) [of both immunoglobulin G (IgG) and IgM class].

RESULTS

A significant association was found between laboratory and clinical features of APS; odds ratios (ORs) for thrombosis associated with the presence of LA, aCL, and anti-beta(2)GPI Abs were 4.04 [95% CI: 2.44-6.68], 3.71 (95% CI 2.32-5.92) and 2.57 (95% CI 1.60-4.1), respectively. Detailed analysis showed marked differences between the risk of clinical complications associated with the presence of an antibody in the IgG class (OR 4.15, 95% CI 2.42-7.12, and OR 4.77, 95% CI 2.37-9.61 for aCL and anti-beta(2)GPI, respectively) and in the IgM class (OR 2.2, 95% CI 1.31-3.70, and OR 1.9, 95% CI 1.15-3.14 for aCL and anti-beta(2)GPI, respectively). The postulated inclusion of anti-beta(2)GPI antibody positivity into the previous laboratory criteria changed only slightly the number of patients diagnosed with APS (from 112 to 117).

CONCLUSIONS

The updated APS classification criteria clearly represent a step forward. However, our results argue against the use of overall positivity for aCL or anti-beta(2)GPI, and favor a clear distinction between the IgG and IgM classes of antiphospholipid ABs. Patients with both LA and anti-beta(2)GPI IgG or LA and aCL IgG positivity may represent the subgroups at the highest risk of thrombotic complications.