Prevalence and clinical correlates of anti‐phospholipid antibodies in South Africans with systemic lupus erythematosus

Chylomicronemia from GPIHBP1 autoantibodies

Some cases of chylomicronemia are caused by autoantibodies against glycosylphosphatidylinositol-anchored HDL binding protein 1 (GPIHBP1), an endothelial cell protein that shuttles LPL to the capillary lumen. GPIHBP1 autoantibodies prevent binding and transport of LPL by GPIHBP1, thereby disrupting the lipolytic processing of triglyceride-rich lipoproteins. Here, we review the "GPIHBP1 autoantibody syndrome" and summarize clinical and laboratory findings in 22 patients. All patients had GPIHBP1 autoantibodies and chylomicronemia, but we did not find a correlation between triglyceride levels and autoantibody levels. Many of the patients had a history of pancreatitis, and most had clinical and/or serological evidence of autoimmune disease. IgA autoantibodies were present in all patients, and IgG4 autoantibodies were present in 19 of 22 patients. Patients with GPIHBP1 autoantibodies had low plasma LPL levels, consistent with impaired delivery of LPL into capillaries. Plasma levels of GPIHBP1, measured with a monoclonal antibody-based ELISA, were very low in 17 patients, reflecting the inability of the ELISA to detect GPIHBP1 in the presence of autoantibodies (immunoassay interference). However, GPIHBP1 levels were very high in five patients, indicating little capacity of their autoantibodies to interfere with the ELISA. Recently, several GPIHBP1 autoantibody syndrome patients were treated successfully with rituximab, resulting in the disappearance of GPIHBP1 autoantibodies and normalization of both plasma triglyceride and LPL levels. The GPIHBP1 autoantibody syndrome should be considered in any patient with newly acquired and unexplained chylomicronemia.

High IgA antiphospholipid autoantibodies in healthy Sudanese explain the increased prevalence among Sudanese compared to Swedish systemic lupus erythematosus patients

Objectives

IgA antiphospholipid antibodies (aPL) are prevalent in systemic lupus erythematosus (SLE) patients of African American, Afro-Caribbean and South African origin. Nevertheless, data from North Africa are lacking, and most studies use manufacturer-suggested cut-offs based on Caucasian controls. Therefore, we compared aPL isotypes in Sudanese and Swedish SLE patients using nation-based cut-offs.

Methods

Consecutive SLE patients and age- and sex-matched controls from Sudan (N = 115/106) and Sweden (N = 340/318) were included. All patients fulfilled the 1982 American College of Rheumatology SLE classification criteria. Antiphospholipid syndrome–related events were obtained from patients’ records. IgA/G/M anticardiolipin and anti-β₂ glycoprotein I (β₂GPI) were analysed with two independent assays. IgA anti-β₂GPI domain 1 (D1) was also investigated. Manufacturers’ cut-offs and the 95th and 99th percentile cut-offs based on national controls were used.

Results

Sudanese patients and controls had higher levels and were more often positive for IgA aPL than Swedes when using manufacturers’ cut-offs. In contrast, using national cut-offs, the increase in IgA aPL among Sudanese patients was lost. Occurrence of IgA anti-D1 did not differ between the countries. Venous thromboses were less common among Sudanese patients and did not associate with aPL. No clinical associations were observed with IgA anti-β₂GPI in Sudanese patients. Thromboses in Swedes were associated with IgG/M aPL. Fetal loss was associated with aPL in both cohorts.

Conclusions

IgA anti-β₂GPI prevalence was higher among Sudanese compared to Swedish patients when manufacturers’ cut-offs were used. This situation was reversed when applying national cut-offs. Anti-D1 was not increased in Sudanese patients. Previous studies on populations of African origin, which demonstrate a high prevalence of IgA aPL positivity, should be re-evaluated using a similar cut-off approach.

Elevated IgA antiphospholipid antibodies in healthy pregnant women in Sudan but not Sweden, without corresponding increase in IgA anti-β2 glycoprotein I domain 1 antibodies

Objective

The role of antiphospholipid antibodies (aPL) during apparently normal pregnancy is still unclear. IgA aPL are prevalent in populations of African origin. Our aim was to measure all isotypes of anticardiolipin (anti-CL) and anti–β₂ glycoprotein I (anti-β₂GPI) in healthy pregnant and non-pregnant women of different ethnicities.

Methods

Healthy Sudanese pregnant women (n = 165; 53 sampled shortly after delivery), 96 age-matched Sudanese female controls and 42 healthy pregnant and 249 non-pregnant Swedish women were included. IgA/G/M anti-CL and anti-β₂GPI were tested at one time point only with two independent assays in Sudanese and serially in pregnant Swedes. IgA anti-β₂GPI domain 1 and as controls IgA/G/M rheumatoid factor (RF), IgG anti–cyclic citrullinated peptide 2 (anti-CCP2) and anti–thyroid peroxidase (anti-TPO) were investigated in Sudanese females.

Results

Pregnant Sudanese women had significantly higher median levels of IgA anti-CL, IgA anti-β₂GPI (p < 0.0001 for both antibodies using two assays) and IgM anti-β₂GPI (both assays; p < 0.0001 and 0.008) compared with non-pregnant Sudanese. IgA anti-CL and anti-β₂GPI occurrence was increased among Sudanese pregnant women compared with national controls. No corresponding increase during pregnancy was found for IgA anti-β₂GPI domain 1 antibodies. Both IgG anti-CL and IgG control autoantibodies decreased during and directly after pregnancy among Sudanese. Serially followed Swedish women showed no changes in IgA aPL, whereas IgG/M anti-CL decreased.

Conclusions

IgA aPL are increased in Sudanese but not in Swedish women, without corresponding increase in IgA domain 1. Whether due to ethnicity and/or environmental influences the occurrence of IgA aPL during Sudanese pregnancies, and its clinical significance, is yet to be determined.

Occurrence of anti-CCP2 and RF isotypes and their relation to age and disease severity among Sudanese patients with rheumatoid arthritis

OBJECTIVE

Anti-cyclic citrullinated peptide 2 antibodies (anti-CCP2) and rheumatoid factor (RF) in rheumatoid arthritis (RA) has been extensively assessed in industrialized countries. We investigated the diagnostic and prognostic impact of anti-CCP2 and RF isotypes in a Sudanese cross-sectional RA cohort.

METHODS

Consecutive RA patients (n = 281) diagnosed according to the 1987 ACR criteria were included 2008-2010. Anti-CCP2 and RF isotypes (IgA, IgM, and IgG) were measured by enzyme immunoassay in 262 patients, with reference intervals aligned to the same diagnostic specificity as for anti-CCP2 (97.6%) using national controls.

RESULTS

IgA RF was the predominant RA-associated autoantibody (56%), followed by IgM RF and anti-CCP2 (both 52%) and IgG RF (49%). In receiver operator characteristic analysis, IgA RF also showed the largest area under the curve. Patients with IgG RF were younger and had 8 years lower median age of disease onset compared to antibody negative patients (p < 0.0001). IgG RF was the only marker associated with a high number of involved joints (p = 0.028), and together with anti-CCP2 were the strongest markers for finger deformities (p = 0.016 and p = 0.012), respectively. No statistical differences were found for disease duration, ESR and Hb levels, and occurrence of erosions/osteopenia for any of the investigated autoantibodies.

CONCLUSION

Whereas IgA RF showed the best diagnostic performance, IgG RF associated with low age of RA onset, high number of involved joints, and finger deformities. These findings indicate that RA-associated antibodies other than conventional IgM RF and anti-CCP2 might be informative in non-Caucasian RA populations.

IgG/IgM antiphospholipid antibodies present in the classification criteria for the antiphospholipid syndrome: a critical review of their association with thrombosis

Essentials The clinical value of IgM antibodies in thrombotic antiphospholipid syndrome (APS) is debated. By review of literature, we reconsidered the clinical value of IgM antibodies in thrombotic APS. More significant correlations with thrombosis were found for the IgG compared to IgM isotype. Unavailability of paired IgG/IgM results hampers evaluating the added value of IgM positivity. Click to hear Dr de Groot's perspective on antiphospholipid syndrome

SUMMARY

Background Despite the update of the classification criteria for the antiphospholipid syndrome (APS), difficulties persist in the identification of patients at risk for thrombosis. Current guidelines include assays detecting IgG/IgM anti-β2 -glycoprotein I and anti-cardiolipin antibodies, although the relevance of IgM antibodies has been debated. Objectives Through a review of the literature from 2001 to 2014, we aimed to formally establish the thrombotic risk stratification potential of IgM as compared with IgG anti-phospholipid antibodies (aPLs). Patients/methods One thousand two hundred and twenty-eight articles were selected by a computer-assisted search of the literature. Of the 177 studies that met our inclusion criteria, the clinical value of IgG/IgM aPLs was established through analysis of odds ratios for thrombosis or percentage of positives in the thrombotic population. Results/conclusions We clearly found more significant correlations with thrombosis for the IgG than for the IgM isotype. Nonetheless, in a minority of studies, significant associations with thrombosis were found for IgM but not IgG antibodies. The unavailability of paired results of IgG and IgM for each separate patient hampers evaluation of the added value of isolated IgM positivity. To fully take advantage of results obtained by future studies, we strongly encourage scientists to provide all studied information per patient. We planned a large multicenter study to investigate clinical associations of isolated/combined positivity for criteria/non-criteria aPLs. Importantly, because of the presence of non-pathogenic aPLs, quantitative assays are characterized by a high false-positivity rate. Optimization of functional assays, such as thrombin generation measuring the whole scheme of coagulation, may help to reduce APS-related morbidity and mortality.

The coexistence of antiphospholipid syndrome and systemic lupus erythematosus in Colombians

OBJECTIVES

To examine the prevalence and associated factors related to the coexistence of antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE) in a cohort of Colombian patients with SLE, and to discuss the coexistence of APS with other autoimmune diseases (ADs).

METHOD

A total of 376 patients with SLE were assessed for the presence of the following: 1) confirmed APS; 2) positivity for antiphospholipid (aPL) antibodies without a prior thromboembolic nor obstetric event; and 3) SLE patients without APS nor positivity for aPL antibodies. Comparisons between groups 1 and 3 were evaluated by bivariate and multivariate analysis.

RESULTS

Although the prevalence of aPL antibodies was 54%, APS was present in just 9.3% of SLE patients. In our series, besides cardiovascular disease (AOR 3.38, 95% CI 1.11-10.96, p = 0.035), pulmonary involvement (AOR 5.06, 95% CI 1.56-16.74, p = 0.007) and positivity for rheumatoid factor (AOR 4.68, 95%IC 1.63-14.98, p = 0.006) were factors significantly associated with APS-SLE. APS also may coexist with rheumatoid arthritis, Sjögren's syndrome, autoimmune thyroid diseases, systemic sclerosis, systemic vasculitis, dermatopolymyositis, primary biliary cirrhosis and autoimmune hepatitis.

CONCLUSIONS

APS is a systemic AD that may coexist with other ADs, the most common being SLE. Awareness of this polyautoimmunity should be addressed promptly to establish strategies for controlling modifiable risk factors in those patients.

In Black Africans with rheumatoid arthritis, ACPA recognize citrullinated fibrinogen and the derived peptides α36-50Cit38,42 and β60-74Cit60,72,74, like in Caucasians

Well documented in Caucasians and Asians, the diagnostic value of anti-CCP2 antibodies has been confirmed in Black African populations. However, autoantibodies to other citrullinated peptides/proteins and their fine specificities have not yet been studied. Here, we show that in Cameroonian patients, anti-citrullinated fibrinogen autoantibodies (AhFibA) are sensitive (73%) diagnostic markers for RA. We also determine that autoantibodies directed to α36-50Cit38,42 or β60-74Cit60,72,74 peptides which bear the immunodominant epitopes of citrullinated fibrin, are present in similar proportions in Black Africans and Caucasians with 25/56 (45%) and 41/56 (73%) positive RA-sera in Cameroonians, respectively. They also account for almost all the AhFibA reactivities since 38/41 (93%) AhFibA-positive sera contain anti-α36-50Cit38,42 and/or anti-β60-74Cit60,72,74 autoantibodies. Finally, HLA-DRB1 SE alleles were associated with higher titres of AhFibA and anti-β60-74Cit60,72,74 autoantibodies. In the genetic and environmental backgrounds of Black Africans, AhFibA are a hallmark of RA like in Caucasians, moreover they recognize the same fibrin epitopes.

Antiphospholipid syndrome in 2014: more clinical manifestations, novel pathogenic players and emerging biomarkers

The clinical spectrum of the anti-phospholipid syndrome (APS) is not limited to vascular thrombosis or miscarriages but includes additional manifestations that cannot be explained solely by a thrombophilic state. Anti-cardiolipin, anti-beta₂ glycoprotein I (anti-β₂GPI) and lupus anticoagulant (LA) assays are not only the formal diagnostic and classification laboratory tools but also parameters to stratify the risk to develop the clinical manifestations of the syndrome. In particular, anti-β₂GPI antibodies reacting with an immunodominant epitope on domain I of the molecule were reported as the prevalent specificity in APS patients, correlating with a more aggressive clinical picture. Several laboratory assays to improve the diagnostic and predictive power of the standard tests have been proposed. Plates coated with the phosphatidylserine-prothrombin complex for detecting antibodies represent a promising laboratory tool correlating with LA and with clinical manifestations. Anti-phospholipid antibodies can be found in patients with full-blown APS, in those with thrombotic events or obstetric complications only or in asymptomatic carriers. An inflammatory second hit is required to increase the presence of β₂GPI in vascular tissues, eventually triggering thrombosis. Post-transcriptional modifications of circulating β₂GPI, different epitope specificities or diverse anti-β₂GPI antibody-induced cell signaling have all been suggested to affect the clinical manifestations and/or to modulate their occurrence.

Anti-prothrombin (aPT) and anti-phosphatidylserine/prothrombin (aPS/PT) antibodies and the risk of thrombosis in the antiphospholipid syndrome. A systematic review

Antibodies to prothrombin are detected by directly coating prothrombin on irradiated ELISA plates (aPT) or by using the phosphatidylserine/prothrombin complex as antigen (aPS/PT). Although these antibodies have both been associated with antiphospholipid syndrome (APS) and a correlation between the two assays have been reported, it seems that aPT and aPS/PT belong to different populations of autoantibodies. It was our objective to systematically review the available evidence on aPT and aPS/PT antibodies and the risk of thrombosis in APS. Medline-reports published between 1988 and 2013 investigating aPT and aPS/PT as a risk factor for thrombosis were included. Whenever possible, antibody isotype(s) and site of thrombosis were analysed. This systematic review is based on available data from more than 7,000 patients and controls from 38 studies analysing aPT and 10 aPS/PT. Antibodies to prothrombin (both aPT and aPS/PT) increased the risk of thrombosis (odds ratio [OR] 2.3; 95% confidence interval [CI] 1.72-3.5). aPS/PT seemed to represent a stronger risk factor for thrombosis, both arterial and/or venous than aPT (OR 5.11; 95%CI 4.2-6.3 and OR 1.82; 95%CI 1.44-2.75, respectively). In conclusion, routine measurement of aPS/PT (but not aPT) might be useful in establishing the thrombotic risk of patients with previous thrombosis and/or systemic lupus erythematosus. Their inclusion as laboratory criteria for the APS should be indisputably further explored.

The implications of autoimmunity and pregnancy

There are multiple epidemiological studies that document the potential adverse affects of autoimmunity on nearly every aspect of reproduction, even in the absence of clinically manifest autoimmune disease. Two decades ago, it was suggested that women with autoimmune diseases avoid pregnancy due to inordinate risks to the mother and the child. In contrast, newer epidemiological data demonstrated that advances in the treatment of autoimmune diseases and the management of pregnant women with these diseases have similarly improved the prognosis for mother and child. In particular, if pregnancy is planned during periods of inactive or stable disease, the result often is giving birth to healthy full-term babies without increased risks of pregnancy complications. Nonetheless, pregnancies in most autoimmune diseases are still classified as high risk because of the potential for major complications. These complications include disease exacerbations during gestation and increased perinatal mortality and morbidity in most autoimmune diseases, whereas fetal mortality is characteristic of the anti-phospholipid syndrome (APS). In this review, we will discuss these topics, including issues of hormones, along with potential long-term effects of the microchimerism phenomenon. With respect to pregnancy and autoimmune diseases, epidemiological studies have attempted to address the following questions: 1) Is it safe for the mother to become pregnant or are there acute or chronic effects of pregnancy on the course of the disease? 2) Does the disease alter the course and/or the outcome of a pregnancy and thereby represent an inordinate risk for the fetus and infant? And do new therapeutic and management approaches improve the pregnancy outcomes in women with autoimmune diseases? 3) Does passage of maternal autoantibodies represent a risk to the child? 4) Do pregnancy, parity, or other factors influencing hormonal status explain the female predominance of many autoimmune diseases, and is the pregnancy effect related to microchimerism? Answering these questions has taken on additional importance in recent decades as women in western countries now frequently choose to delay pregnancies and have some or all of their pregnancies after disease onset. In this paper, we primarily focus on APS, systemic lupus erythematosus (SLE), multiple sclerosis (MS), rheumatoid arthritis (RA), and type 1 diabetes (T1D).

Thrombosis risk in systemic lupus erythematosus: the role of thrombophilic risk factors

OBJECTIVES

Thromboembolic episodes are frequent manifestations of systemic lupus erythematosus (SLE). Although the presence of anti-phospholipid antibodies (aPL) is known to contribute to thromboembolism (TE), the relative contribution of other TE risk factors is unknown. The aim of this study was to determine the prevalence of TE in a Caucasian SLE population, to identify the risk factors of highest importance, and to assess the clinical value of thrombophilia screening among SLE patients.

METHODS

Samples from 105 patients were analysed with a screen including aPL, activated protein C resistance, factor V Leiden (FVL) and prothrombin G20210A mutations; protein C, protein S and antithrombin activity; factor VIII (FVIII) and von Willebrand factor (vWF), and homocysteine (Hcy) levels.

RESULTS

The annual incidence of arterial and venous TE events in our SLE population was 5.4 and 12.4 per 1000, respectively. The highest risk of thrombosis was carried by the simultaneous presence of lupus anticoagulant (LA) and anti-cardiolipin (aCL) [relative risk (RR) = 4.03, 95% confidence interval (CI) 2.06-7.86] or anti-beta2-glycoprotein I antibodies (abeta2-GPI) (RR = 5.10, 95% CI 2.58-10.1). Positivity for the individual aPL tests all carried an elevated TE risk. The presence of other risk factors seemed to be of less importance.

CONCLUSIONS

In SLE patients, the presence of aPL is a more significant risk factor for the development of thrombosis than the known inherited deficiencies. Based on these data, routine screening for additional hereditary risk factors seems to be unwarranted.