Association between HLA class II antigens and primary antiphospholipid syndrome from the south of Spain

Multiple autoimmune syndrome: Clinical, immunological and genotypic characterization

INTRODUCTION

The existence of subphenotypes common to several autoimmune diseases (AIDs) suggests a shared physiopathology - autoimmune tautology. Multiple Autoimmune Syndrome (MAS) - the coexistence of three or more AIDs in one person-, best illustrates that polyautoimmunity is more than a coincidence.

OBJECTIVES

Characterize and compare the monoautoimmune and MAS patients. Understand if clustering of AIDs leads to differences in disease severity, autoantibodies expression or genetic polymorphisms that could be markers for polyautoimmunity.

METHODS

Currently adult patients were selected from unit cohort. MAS was assumed when ≥3 AIDs were present. 343 patients were included after exclusion criteria: having two AIDs or undetermined diagnosis. Clinical and immunological data were collected from medical files. HLA-DRB1 was genotyped by PCR-SSP methodology and PTPN22(rs2476601) polymorphisms by TaqMan Real Time PCR. Data were analysed using Chi-Square, Fisher's exact tests and logistic regression. Odds ratios (OR) and 95% confidence intervals were calculated.

RESULTS

In comparison with control population: ELEVATED FREQUENCIES: HLA-DRB1*03 in study cohort (OR=3.68,p<0.001) and in monoautoimmune SLE (OR=2.79,p<0.001) and SjS (OR=8.27,p<0.001); HLA-DRB1*15 in monoautoimmune SjS (OR=2.39,p = 0.011); HLA-DRB1*16 in MAS SLE (OR=2.67,p = 0.031); PTPN22_T in all groups except monoautoimmune SjS and triple positive systemic MAS.

DIMINISHED FREQUENCIES

HLA-DRB1*11 in study cohort (OR=0.57,p = 0.013), in MAS SLE (OR=0.39,p = 0.031) and monoautoimmune SjS (OR=0.10,p = 0.005); HLA-DRB1*13 in study cohort (OR=0.52,p = 0.001) and in monoautoimmune SLE (OR=0.53,p = 0.009) and SjS (OR=0.38,p = 0.031); HLA-DRB1*14 in study cohort (OR=0.32,p = 0.013) and monoautoimmune SLE (OR=0.21,p = 0.021); SLE group: HLA-DRB1*07 frequency was higher in monoautoimmune patients (OR=0.43,p = 0.023). MAS patients had significantly more NPSLE (OR=2.99,p<0.001), subacute cutaneous lesions (OR=2.30,p = 0.037), muscle&tendon (OR=2.00,p = 0.045), and haematological (OR=3.18,p = 0.006) involvement and Raynaud's (OR=2.94,p<0.001). SjS group: MAS patients had more frequently cryoglobulins (OR=2.96,p = 0.030), low complement (OR=2.43,p = 0.030) and Raynaud's (OR=4.38,p<0.001); monoautoimmune patients had more parotid enlargement (OR=0.12,p<0.001). APS group: MAS patients had more non-thrombotic manifestations (OR=4.69,p = 0.020) and Raynaud's (OR=9.12,p<0.001). Triple positive systemic MAS (SLE+SjS+APS) had more frequently severe kidney involvement (OR=11.67,p = 0.021) and CNS thrombosis (OR=4.44,p = 0.009). Anti-U1RNP increased frequency was transversally attributable to MAS.

CONCLUSIONS

The coexistence of AIDs contributes to a more severe disease course. We confirmed previously established genetic risk and protection factors and suggest a new protective one - HLA-DRB1*14. HLA-DRB1*07 and anti-U1RNP could be markers for mono and polyautoimmunity, respectively; HLA-DRB1*13 could be a predictor for vascular risk in patients with multiple AIDs. PTPN22(rs2476601) polymorphism could be associated with less severe disease.

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.

Genetics of Antiphospholipid Syndrome

PURPOSE OF REVIEW

Antiphospholipid syndrome (APS) is a rare heterogenous disorder associated with the presence of antiphospholipid antibodies and can present in a wide variety of clinical manifestations including thrombosis and pregnancy complications. Although the etiology of APS remains poorly understood, there is strong support for considering APS as a complex genetic disease in which multiple genetic risk factors, in conjunction with environmental factors, affect its onset, progression, and severity. Here, we provide a comprehensive review of the current knowledge of the genetic basis of APS, which remains in its infancy.

RECENT FINDINGS

Most genetic studies to date in APS were performed in small cohorts of patients. As a result, only few genetic associations reported are convincing. Several reports suggested genetic associations with HLA class II alleles in APS, and only two genetic loci outside of the HLA region (STAT4 and C1D) reached the threshold for genome-wide level of significance (P < 5 × 10^-8). In this review, we also shed light on the genetic differences among the diverse clinical subsets of APS and briefly discuss the role that DNA methylation changes might play in the pathophysiology of this disease. The genetic basis of APS remains poorly characterized. Larger collaborative multicenter studies using well-characterized patients are needed to comprehensively understand the role of genetic susceptibility in APS.

HLA DRB1 and HLA DQB1 Alleles in Bulgarian Patients with Primary and Secondary Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is an autoimmune disease with multifactorial and polygenic pathogenesis. Recently, the genetic predisposition in APS has been subjected to wide discussion. The aim of this study is to determine the prevalence of DRB1 and DQB1 loci in Bulgarian population of healthy persons and patients with primary (PAPS) and secondary (SAPS) APS. Patients are divided in 5 groups: I-29 patents with systemic lupus erythematosus (SLE) with SAPS, II-35 patients with PAPS, III-32 women with spontaneous abortions without aPL, IV-15 patients with different thrombosis (deep venous thromboses, pulmonary embolism, mesenterial thrombosis, myocardial infarction, stroke) without laboratory data for APS, and V-16 SLE patients without clinical and laboratory data for APS. SAPS patients have more frequently DRB1*03 and DQB1*02 and more rarely DRB1*11 and DQB1*03 in comparison with healthy subjects and patients with PAPS. Patents with PAPS, those with spontaneous abortions and patients with thrombotic events but without antiphospholipid antibodies (aPL) have DRB1*03, DRB1*11, DQB1*02 and DQB1*03 alleles similar to the general population. There are no differences between group I (SLE+APS) and group V (SLE) in DRB1* and DQB1*alleles.

Antiphospholipid syndrome: 30 years and our contribution

In 1983, Graham Hughes first described the concept of antiphospholipid syndrome (APS). In 1984, we described the enzyme-linked immunosorbent assay (ELISA) system which directly detected circulating aCL in patients with systemic lupus erythematosus (SLE) who revealed biological false positive serological test for syphilis. In 1990, three groups, including our group, independently reported the necessity of a cofactor for the binding of autoimmune anticardiolipin antibodies (aCL) to the solid phase phospholipids. β2-glycoprotein I (β2GPI) was identified as this cofactor. In 1994,the epitope for aCL was shown to develop when β2GPI is adsorbed on polyoxygenated polystyrene plates. In 2000, we described antiprothrombin antibodies bind to prothrombin exposed to immobilized phosphatidylserine and established a phosphatidylserine dependent monoclonal antiprothrombin antibody. In 2004, a novel role of nicked β2GPI was identified in the negative feedback pathway of extrinsic fibrinolysis. Nicked β2GPI was found to bind angiostatin 4.5 and to attenuate its antiangiogenic property. In 2004, we demonstrated that the p38 MAPK pathway mediates induction of the TF gene in stimulated with human monoclonal anti- β2GPI antibodies. Very recently, β2GPI was identified as a complement regulator. The cross-link between complement activation and prothrombotic status in patients with APS has been drawn much attention. Genetic factors are hypothesized to play a role in the susceptibility to APS based on several family studies in patients with antiphospholipid antibodies (aPL) and/or clinical manifestations of APS. The genetics of β2GPI has been extensively studied. 247 Val/Leu polymorphism can affect the conformational change of β2-GPI and the exposure of the epitopes for aCL. We found that 247 Val was correlated with anti-β2-GPI production in patients with primary APS, and 247 Val may be important for β2-GPI antigenicity. STAT4 SNP in Japanese patients with SLE and/or APS. T allele frequencies in SLE and APS were significantly elevated compared with that in healthy controls. When analyzed only in primary APS patients, T allele frequency was further higher. BANK1, BLK and SNP in 1q25.1 region were associated with not only SLE but also APS in Japanese population. These results suggest that APS and SLE, in part, share a common genetic background.

Familial lupus and antiphospholipid syndrome

The occurrence of systemic lupus erythematosus (SLE) in several members of a family has spurred intense efforts to identify susceptibility genes predisposing to the disease. As a result, a number of candidate association genes in different ethnic groups have been identified, and some genes have been linked to specific lupus manifestations. Particularly where familial disease occurs in childhood, and especially when it occurs prior to puberty, complement deficiencies and other immunologic defects should be explored. Evidence of other forms of autoimmunity, including autoimmune thyroiditis and antiphospholipid syndrome (APS), is common in families with SLE. Familial APS is uncommon in the absence of other thrombophilic defects, but occasionally is seen with apparent autosomal dominant inheritance. Thus far, no firm gene associations have been identified for APS, in part because of the rarity of multiplex families to study. A search for other familial causes of thrombotic disease should be performed when APS occurs in more than one family member.

Histocompatibility class I and II antigens in extensive kindred with Sneddon's syndrome and related hypercoagulation disorders

We have studied the relationship between the histocompatibility class I and II antigens and Sneddon's syndrome (SS) in a Spanish patient with SS and her relatives (13 available members of an extensive 3-generation pedigree with diverse autoimmune hypercoagulation abnormalities). The patient and her father were diagnosed with a primary antiphospholipid antibody syndrome and were HLA-A30-B13-Bw6. In addition, a HLA-Bw6-DQ1 association was present in all the members of this kindred. These data suggest that the combination of the histocompatibility class I and II antigens in this family may be a marker for predisposition to SS.

Ethnic and geographical variation in antiphospholipid (Hughes) syndrome

Investigation of the clinical epidemiology of the antiphospholipid syndrome (APS) is in its early stages. During the past 20 years, studies of antiphospholipid antibodies (aPL) and APS have been made in many countries and ethno-geographical groups. aPL appear to occur in all populations studied, with some variations noted in their frequency and in the clinical complications. Environmental and genetic factors contribute to ethnic variation and susceptibility to APS and thus inter-ethnic differences in disease patterns may be due to environmental or genetic factors, or both.

Current debates in antiphospholipid syndrome: the acquired antibody-mediated thrombophilia

Antiphospholipid (APL) syndrome is the most common form of acquired thrombophilia. It can cause significant morbidity and even mortality. The term "APL antibodies" represents a heterogeneous group of antibodies associated with this disorder. Currently no single assay can identify every APL antibody. Clinically relevant APL antibodies are mainly anticardiolipin antibodies (ACA) detected by solid phase enzyme-linked immunosorbent assay (ELISA) and lupus anticoagulants (LA) demonstrated by in vitro coagulation assay. However, there are some other antibodies associated with the APL syndrome (i.e., subgroup APL antibodies). ACAs, LAs, and subgroup APL antibodies represent intersecting, but non-identical, subsets of autoantibodies. Thus, those autoantibodies may coexist or may occur independently. Any organ system and any size of vessel can be affected during the clinical course of the disease. Therefore, the APL syndrome can manifest itself in a wide variety of clinical thrombotic features. Fetal loss and pregnancy morbidity represent a specific challenge. Despite tremendous advances in the understanding of the pathogenesis of APL syndrome during the past decade, the mainstay of management is still anticoagulation. However, there is no general agreement regarding the duration and intensity of anti-coagulant therapy. In this review, we focused on the current dilemmas and their present clarifications in the wide clinicopathologic spectrum of APL syndrome and APL antibody-related distinct pathologic conditions.

HLA class II alleles and genetic predisposition to the antiphospholipid syndrome

The antiphospholipid syndrome (APS) is an autoimmune disease characterized by the presence of antiphospholipid antibodies (aPL). Its etiology is linked to genetic predisposition, which is accounted for, at least in part, by genes of major histocompatibility complex (HLA system). The association of APS with human leukocyte antigen (HLA) alleles is a consequence of the association of aPL with HLA alleles. Some HLA alleles carry the risk to produce aPL, and this is independent of the clinical context. In fact, we find the same associations between HLA and aPL in primary APS and in APS secondary to systemic lupus erythematosus (SLE). The association of HLA-DR4, -DR7, -DRw53 and -DQB1*0302 with aCL that has been demonstrated in primary APS can also be found in SLE, a disease with a completely different pattern of HLA allele association (DR2, DR3, DRw52). In addition, the various aPL (anticardiolipin antibodies, lupus anticoagulant, anti-beta2GPI antibodies, antiphosphatidylserine/prothrombin antibodies) show similar HLA association, again independent of the clinical context (primary APS or SLE), and across various ethnic groups.

Genetics of antiphospholipid syndrome

The mechanisms of thrombosis in antiphospholipid syndrome (APS) are highly heterogeneous and multifactorial, and some genetic factors may be involved in its pathophysiology. The genetic variants of representative antigen, beta 2-glycoprotein I (beta 2GPI), have been known, and valine/leucine247 polymorphism is a genetic risk for having anti beta 2GPI antibodies and APS. Congenital beta 2GPI deficiency did not correlate with thrombophilia, thus its responsible gene (beta 2GPI-Sapporo) was not a risk for thrombosis. Many other thrombosis-related genetic factors have been investigated in APS, but no additional risk for thrombosis has been indicated in patients with antiphospholipid antibodies.

The family history of patients with primary or secondary antiphospholipid syndrome (APS)

OBJECTIVE

To evaluate familial history for evidence of antiphospholipid syndrome (APS) and autoimmune disease in rheumatology department patients with primary or secondary APS.

METHODS

We retrospectively studied patients with APS and systemic lupus erythematosus (SLE) managed at the Rheumatology Department of the Bichat University Hospital, Paris, between 1987 and 1996. Data were collected by chart review and by a 1997 standardized telephone interview.

RESULTS

We identified 108 patients with APS managed during the ten-year study period. According to classical classification criteria, 39 patients had primary antiphospholipid syndrome (PAPS) and 69 secondary antiphospholipid syndrome (SAPS). Family history data were obtained for 29 (74%) and 55 (80%) PAPS and SAPS patients. respectively (78% of the 108 patients). Twelve PAPS (41% and 19 SAPS (35%) patients had one or more relatives with evidence of at least one clinical feature of APS such as thrombosis or recurrent fetal loss; of these patients, seven in the PAPS (24%) and 11 in the SAPS (20%) group had two or more relatives with evidence of a clinical feature of APS. Three PAPS (10%) and 14 SAPS (25%) patients had one or more family members with an autoimmune disease.

CONCLUSION

A positive family history for autoimmune disease and/or antiphospholipid syndrome is common in patients with PAPS or SAPS. This finding supports a genetic contribution to APS. The percentage of a positive family history for autoimmune disease tend to be higher in patients with SAPS than in those with PAPS.

HLA-DR7 in association with chlorpromazine-induced lupus anticoagulant (LA)

The presence of anti-phospholipid antibodies (aPL) has been associated with the major histocompatibility complex (MHC) genes. These autoantibodies occur in individuals with infections such as that produced by the human immunodeficiency virus 1 (HIV-1) or with syphilis, but they can also occur in drug-induced lupus-like syndromes. In the present study, we analysed the presence of aPL (detected as lupus anti-coagulant) and its relationship with the MHC markers in 93 Caucasian psychiatric patients chronically treated with chlorpromazine. Forty-one out of 93 patients were positive for LA, and the HLA-DR7 antigen was significantly increased in LA-positive patients as compared to normal controls or LA-negative patients (PC = 0.024, RR = 2.12 and P = 0.05, RR = 1.57, respectively). Likewise, we noted a significantly increased frequency of HLA-B44 in LA-positive patients as compared to normal controls (PC = 0.024, RR = 2.12), but not when compared to aPL-negative patients. No significant differences were found among any other class I, II or III MHC antigens. Haplotype analysis showed that DR7 was mostly part of the HLA-B44-DR7-FC31 and B7-DR7-SC31 haplotypes. These results suggest that the HLA-DR7 antigen might be playing a role in the production of aPL in chlorpromazine-treated patients.

[Obstetrical complications of antiphospholipid syndrome]

Spontaneous miscarriages and fetal deaths take part of the definition of the antiphospholipid syndrome. Preeclampsia, fetal distress, preterm delivery, intrauterine growth retardation, mother's or newborn's vascular thrombosis are also included in the spectrum of clinical events linked to the antiphospholipid antibodies in pregnant women. The pathogenesis is not fully understood, but involves interactions between antibodies and phospholipidic molecules that are complexed to plasmatic proteins of the coagulation, or present on endothelial cell and platelet surfaces. The poor spontaneous prognosis of pregnancy in the context of the antiphospholipid syndrome is dramatically improved by preventive treatment. Therapeutic options are not codified and are various combinations of low-dose aspirin, heparin, steroids, intravenous immunoglobulins, and fish-oil derivatives. Excellent obstetrical care is mandatory in every case.

Relationship of anticardiolipin antibodies and antiphospholipid syndrome to HLA-DR7 in Mexican patients with systemic lupus erythematosus (SLE)

We studied IgG and IgM anticardiolipin antibodies (aCL) by an ELISA method in 80 Mexican systemic lupus erythematosus (SLE) patients and 378 of their first degree relatives. Sixty five percent of SLE patients and 16% of their relatives were positive for aCL. We also determined allele and haplotype frequencies of Major Histocompatibility Complex (MHC) genes (classes I, II and III) in both patients and relatives. MHC allele and haplotype frequencies of aCL positive and negative individuals were compared to those of normal ethnically matched controls. SLE patients with aCL had statistically significant increased corrected frequencies of HLA-DR3 (pC = 0.04, RR = 2.78); DR7 (pC = 0.005), RR = 3.42) and DQ2 (pC = 0.003, RR = 2.58) antigens. Their first degree relatives positive for aCL also had increased frequency of HLA-DR7 but it did not remain significant after correcting the P value. On the other hand, SLE patients negative for aCL had a moderate increased frequency of DR3 and DQ2 but not of DR7. These results suggest that DR7 associates with the presence of aCL. The distribution of MHC alleles in SLE patients positive for aCL resembles that found in their aCL positive first degree relatives. Since the presence of the antibody is not sufficient to predict a clinical outcome, we studied those patients with reliable clinical data regarding the presence of the antiphospholipid syndrome (aPLS). SLE patients with aPLS had significantly increased frequency of DR7 (pC = 0.004), as did those with probable aPLS (pC = 0.05), while the frequency of DR7 in SLE patients in the doubtful or negative aPLS categories was no different from normal controls. These data support a possible role of DR7 in the development of aCL in SLE patients and their relatives and suggest a contribution of this class II MHC antigen to the development of aPLS within SLE.

Pathogenesis of the antiphospholipid antibody syndrome

Endothelial and/or platelet activation likely initiates thrombus formation. Whether antiphospholipid antibody (aPL) is an activator, a toxic response, or a protective response is not clear, nor is it certain whether aPL is germ-line encoded or antigen-driven. The pregnancy model is particularly informative. Alternative hypotheses about thrombogenicity which relegate aPL to the role of bystander have not yet been excluded.

Genetic risk factors for aPL syndrome

MHC class II alleles and C4 deficiency alleles have been variably associated with aPL syndrome, but the extensive linkage disequilibrium among many of these alleles has made it difficult to assign a causal role for any of them. Interethnic studies of these and other alleles in large cohorts of subjects would help to clarify the roles of these alleles in aPL syndrome.

Histocompatibility genes in antiphospholipid antibody syndrome

The class II and especially the DQB1 locus of MHC genes, as well as C4 deficiency alleles appear to be associated with genetic risk for developing aPL. The extensive linkage disequilibrium among some of these risk factors makes it difficult to assign a causal role for any of these alleles by means of previous population studies of patients with APS; studies a patients with primary APS, in particular, have involved relatively few patients. Although there appear to be some overall similarities between the known MHC associations of primary APS and those of secondary APS, only a modest relative risk of APS is associated with MHC alleles, as discussed above, and other unknown risk factors must also be important. Whether these unknown risk factors for primary APS are different from those in secondary APS is an area for further investigation. In addition, new genes continue to be identified in the MHC class II and III regions that appear to have important roles in antigen processing and recognition. Interethnic studies of these and other alleles in large cohorts would be informative since ethnic groups of African, Japanese or Caucasian backgrounds often exhibit differing allelic linkage disequilibria within the MHC. Studies of linkage relationships in various MHC haplotypes have, for example, helped to clarify the role of MHC class II oligo alleles in rheumatoid arthritis. Further clarification of the roles of these MHC alleles will also depend on functional studies in experimental models and in vitro, to assess the roles of these risk factors in aPL production. The roles of non-MHC risk factors and of environmental agents that are operative within families also warrant further studies.