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1.  Lupus risk variants in the PXK locus alter B-cell receptor internalization 
Frontiers in Genetics  2015;5:450.
Genome wide association studies have identified variants in PXK that confer risk for humoral autoimmune diseases, including systemic lupus erythematosus (SLE or lupus), rheumatoid arthritis and more recently systemic sclerosis. While PXK is involved in trafficking of epidermal growth factor Receptor (EGFR) in COS-7 cells, mechanisms linking PXK to lupus pathophysiology have remained undefined. In an effort to uncover the mechanism at this locus that increases lupus-risk, we undertook a fine-mapping analysis in a large multi-ancestral study of lupus patients and controls. We define a large (257kb) common haplotype marking a single causal variant that confers lupus risk detected only in European ancestral populations and spans the promoter through the 3′ UTR of PXK. The strongest association was found at rs6445972 with P < 4.62 × 10−10, OR 0.81 (0.75–0.86). Using stepwise logistic regression analysis, we demonstrate that one signal drives the genetic association in the region. Bayesian analysis confirms our results, identifying a 95% credible set consisting of 172 variants spanning 202 kb. Functionally, we found that PXK operates on the B-cell antigen receptor (BCR); we confirmed that PXK influenced the rate of BCR internalization. Furthermore, we demonstrate that individuals carrying the risk haplotype exhibited a decreased rate of BCR internalization, a process known to impact B cell survival and cell fate. Taken together, these data define a new candidate mechanism for the genetic association of variants around PXK with lupus risk and highlight the regulation of intracellular trafficking as a genetically regulated pathway mediating human autoimmunity.
PMCID: PMC4288052  PMID: 25620976
lupus; PXK; fine-mapping; B cells; BCR
2.  A Polymorphism in TLR2 Is Associated With Arterial Thrombosis in a Multiethnic Population of Patients With Systemic Lupus Erythematosus 
Thrombosis is a serious complication of systemic lupus erythematosus (SLE). Studies that have investigated the genetics of thrombosis in SLE are limited. We undertook this study to assess the association of previously implicated candidate genes, particularly Toll-like receptor (TLR) genes, with pathogenesis of thrombosis.
We genotyped 3,587 SLE patients from 3 multiethnic populations for 77 single-nucleotide polymorphisms (SNPs) in 10 genes, primarily in TLRs 2, 4, 7, and 9, and we also genotyped 64 ancestry-informative markers (AIMs). We first analyzed association with arterial and venous thrombosis in the combined population via logistic regression, adjusting for top principal components of the AIMs and other covariates. We also subjected an associated SNP, rs893629, to meta-analysis (after stratification by ethnicity and study population) to confirm the association and to test for study population or ethnicity effects.
In the combined analysis, the SNP rs893629 in the KIAA0922/TLR2 region was significantly associated with arterial thrombosis (logistic P = 6.4 × 10−5, false discovery rate P = 0.0044). Two additional SNPs in TLR2 were also suggestive: rs1816702 (logistic P = 0.002) and rs4235232 (logistic P = 0.009). In the meta-analysis by study population, the odds ratio (OR) for arterial thrombosis with rs893629 was 2.44 (95% confidence interval 1.58–3.76), without evidence for heterogeneity (P = 0.78). By ethnicity, the effect was most significant among African Americans (OR 2.42, P = 3.5 × 10−4) and European Americans (OR 3.47, P = 0.024).
TLR2 gene variation is associated with thrombosis in SLE, particularly among African Americans and European Americans. There was no evidence of association among Hispanics, and results in Asian Americans were limited due to insufficient sample size. These results may help elucidate the pathogenesis of this important clinical manifestation.
PMCID: PMC4269184  PMID: 24578102
3.  Value of Isolated IgA anti-β2GPI Positivity in the Diagnosis of the Antiphospholipid Syndrome 
Arthritis and rheumatism  2013;65(12):3186-3193.
To examine the prevalence of isolated IgA anti-β2Glycoprotein I (anti-β2GPI) positivity and the association of these antibodies, and a subgroup that bind specifically to domain IV/V of β2GPI, with clinical manifestations of the Antiphospholipid Syndrome (APS) in three patients groups. The pathogenicity of IgA anti-β2GPI was also evaluated in a mouse model of thrombosis.
Patients with systemic lupus erythematosus (SLE) from a multiethnic, multicenter cohort (LUpus in MInorities, NAture versus nurture [LUMINA]) (n=558), patients with SLE from the Hopkins Lupus Cohort (n=215), and serum samples referred to the Antiphospholipid Standardization Laboratory (APLS) (n=5,098) were evaluated. IgA anti-β2GPI titers and binding to domain IV/V of β2GPI were examined by enzyme-linked immunosorbent assay (ELISA). CD1 mice were inoculated with purified IgA anti- β2GPI antibodies, and surgical procedures and ELISAs were performed to evaluate thrombus development and tissue factor (TF) activity.
A total of 198 patients were found to be positive for IgA anti-β2GPI isotype, and 57 patients were positive exclusively for IgA anti-β2GPI antibodies. Of these, 13 of 23 patients (56.5%) in the LUMINA cohort, 17 of 17 patients (100%) in the Hopkins cohort, and 10 of 17 patients (58.9%) referred to APLS had at least one APS-related clinical manifestation. Fifty-four percent of all the IgA anti-β2GPI positive serum samples reacted with domain IV/V of anti-β2GPI, and 77% of those had clinical features of APS. Isolated IgA anti-β2GPI positivity was associated with an increased risk for arterial thrombosis (p<0.001), venous thrombosis (p=0.015) and all thrombosis (p<0.001). The association between isolated IgA anti-β2GPI and arterial thrombosis (p=0.0003) and all thrombosis (p=0.0003) remained significant after adjusting for other risk factors for thrombosis. In vivo mouse studies demonstrated that IgA anti-β2GPI antibodies induced significantly larger thrombi and higher TF levels compared to controls.
Isolated IgA anti-β2GPI positive titers may identify additional patients with clinical features of APS. Testing for these antibodies when other antiphospholipid (aPL) tests are negative and APS is suspected is recommended. IgA anti-β2GPI antibodies directed to domain IV/V of β2GPI represent an important subgroup of clinically relevant antiphospholipids.
PMCID: PMC4048705  PMID: 23983008
4.  Non-Lymphoma Hematological Malignancies in Systemic Lupus Erythematosus 
Oncology  2013;85(4):10.1159/000350165.
To describe non-lymphoma hematological malignancies in SLE.
A large SLE cohort was linked to cancer registries. We examined the types of non-lymphoma hematological cancers.
In 16, 409 patients, 115 hematological cancers (including myelodysplastic syndrome) occurred. Among these, 33 were non-lymphoma. Of the 33 non-lymphoma cases, 13 were of lymphoid lineage: multiple myeloma (N=5), plasmacytoma (N=3), B-cell chronic lymphocytic leukemia, B-CLL (N=3), precursor cell lymphoblastic leukemia (N=1), and unspecified lymphoid leukemia (N=1). The remaining 20 cases were of myeloid lineage: myelodysplastic syndrome, MDS (N=7), acute myeloid leukemia, AML (N=7), chronic myeloid leukemia, CML (N=2), and 4 unspecified leukemias. Most of these malignancies occurred in female Caucasians, except for plasma cell neoplasms (4/5 multiple myeloma and 1/3 plasmacytoma cases occurred in blacks).
In this large SLE cohort, the most common non-lymphoma hematological malignancies were myeloid types (MDS and AML). This contrasts to the general population, where lymphoid types are 1.7 times more common than myeloid non-lymphoma hematological malignancies. Most (80%) multiple myeloma cases occurred in blacks, which requires further investigation.
PMCID: PMC3880772  PMID: 24107608
Systemic lupus erythematosus; malignancy; cancer
7.  Is Familial Lupus Different from Sporadic Lupus?: Data from LUMINA, a Multiethnic US Cohort 
Lupus  2010;19(11):1331-1336.
To characterize the clinical features of familial lupus, and determine its influence on damage accrual and survival using data from LUMINA, a longitudinal multiethnic US cohort.
Familial lupus was defined as patients with a first degree relative with SLE. Relative risks were estimated by logistic regression; odds ratios (OR) and their 95% confidence intervals (CI) were the measure of association for familial lupus. Hazard Ratios (HR) were calculated using Cox proportional hazard adjusted for potential confounders for damage and survival.
Thirty-two of 644 patients had familial and 612 had sporadic lupus; both groups were of comparable age (~ 36 years). Familial lupus patients were in decreasing order of frequency siblings, parents and children. In multivariable analyses, mucosal ulcers (OR=1.92, 95% CI 0.65–5.70), mitral valve prolapse (OR=1.74, 95% CI 0.50–6.10), cerebrovascular disease (OR=4.18, 95% CI 0.98–17.76) and oral contraceptive use (ever/never; OR=2.51, 95% CI 0.88–7.19) were more likely in familial lupus but a history of low platelet count (<150,000/mm3; OR=0.31, 95% CI 0.08–1.17) and pulmonary disease activity (OR=0.39, 95% CI 0.14–1.20) were less likely. However, none of these associations reached statistical significance. Familial lupus was not significantly associated with a shorter time to either damage accrual or death (HR=0.77, 95% CI 0.37–1.59, p = 0.4746 and HR=0.20, 95% CI 0.03–1.47, p = 0.2020, respectively).
Although some clinical differences were observed in patients with familial and sporadic lupus, familial lupus was not associated with a significantly greater disease burden (damage, survival) than sporadic lupus.
PMCID: PMC4078734  PMID: 20696771
familial lupus; lupus; sporadic lupus; LUMINA; multiethnic cohort
8.  Allelic Dependent Expression of an Activating Fc receptor on B cells Enhances Humoral Immune Responses 
Science translational medicine  2013;5(216):216ra175.
B cells are pivotal regulators of acquired immune responses and recent work in both experimental murine models and humans has demonstrated that subtle changes in the regulation of B cell function can significantly alter immunological responses. The balance of negative and positive signals in maintaining an appropriate B cell activation threshold is critical in B lymphocyte immune tolerance and autoreactivity. FcγRIIb (CD32B), the only recognized Fcγ receptor on B cells, provides IgG-mediated negative modulation through a tyrosine-based inhibition motif which down-regulates B cell receptor initiated signaling. These properties make FcγRIIb a promising target for antibody-based therapy. Here we report the discovery of allele-dependent expression of the activating FcγRIIc on B cells. Identical to FcγRIIb in the extracellular domain, FcγRIIc has a tyrosine-based activation motif in its cytoplasmic domain. In both human B cells and in B cells from mice transgenic for human FcγRIIc, FcγRIIc expression counterbalances the negative feedback of FcγRIIb and enhances humoral responses to immunization in mice and to BioThrax® vaccination in a human Anthrax vaccine trial. Moreover, the FCGR2C-ORF allele is associated with the risk of development of autoimmunity in humans. FcγRIIc expression on B cells challenges the prevailing paradigm of uni-directional negative feedback by IgG immune complexes via the inhibitory FcγRIIb, is a previously unrecognized determinant in human antibody/autoantibody responses, and opens the opportunity for more precise personalized use of B cell targeted antibody-based therapy.
PMCID: PMC3982386  PMID: 24353158
9.  Cancer risk in systemic lupus: An updated international multi-centre cohort study 
Journal of autoimmunity  2013;42:130-135.
To update estimates of cancer risk in SLE relative to the general population.
A multisite international SLE cohort was linked with regional tumor registries. Standardized incidence ratios (SIRs) were calculated as the ratio of observed to expected cancers.
Across 30 centres, 16,409 patients were observed for 121,283 (average 7.4) person-years. In total, 644 cancers occurred. Some cancers, notably hematologic malignancies, were substantially increased (SIR 3.02, 95% confidence interval, CI, 2.48, 3.63), particularly non-Hodgkin’s lymphoma, NHL (SIR 4.39, 95% CI 3.46, 5.49) and leukemia. In addition, increased risks of cancer of the vulva (SIR 3.78, 95% CI 1.52, 7.78), lung (SIR 1.30, 95% CI 1.04, 1.60), thyroid (SIR 1.76, 95% CI 1.13, 2.61) and possibly liver (SIR 1.87, 95% CI 0.97, 3.27) were suggested. However, a decreased risk was estimated for breast (SIR 0.73, 95% CI 0.61–0.88), endometrial (SIR 0.44, 95% CI 0.23–0.77), and possibly ovarian cancers (0.64, 95% CI 0.34–1.10). The variability of comparative rates across different cancers meant that only a small increased risk was estimated across all cancers (SIR 1.14, 95% CI 1.05, 1.23).
These data estimate only a small increased risk in SLE (versus the general population) for cancer over-all. However, there is clearly an increased risk of NHL, and cancers of the vulva, lung, thyroid, and possibly liver. It remains unclear to what extent the association with NHL is mediated by innate versus exogenous factors. Similarly, the etiology of the decreased breast, endometrial, and possibly ovarian cancer risk is uncertain, though investigations are ongoing.
PMCID: PMC3646904  PMID: 23410586
Systemic Lupus Erythematosus; Epidemiology; Treatment; Disease Activity
10.  End-Stage Renal Disease in African Americans With Lupus Nephritis Is Associated With APOL1 
Lupus nephritis (LN) is a severe manifestation of systemic lupus erythematosus (SLE) that exhibits familial aggregation and may progress to end-stage renal disease (ESRD). LN is more prevalent among African Americans than among European Americans. This study was undertaken to investigate the hypothesis that the apolipoprotein L1 gene (APOL1) nephropathy risk alleles G1/G2, common in African Americans and rare in European Americans, contribute to the ethnic disparity in risk.
APOL1 G1 and G2 nephropathy alleles were genotyped in 855 African American SLE patients with LN-ESRD (cases) and 534 African American SLE patients without nephropathy (controls) and tested for association under a recessive genetic model, by logistic regression.
Ninety percent of the SLE patients were female. The mean ± SD age at SLE diagnosis was significantly lower in LN-ESRD cases than in SLE non-nephropathy controls (27.3 ± 10.9 years versus 39.5 ± 12.2 years). The mean ± SD time from SLE diagnosis to development of LN-ESRD in cases was 7.3 ± 7.2 years. The G1/G2 risk alleles were strongly associated with SLE-ESRD, with 25% of cases and 12% of controls having 2 nephropathy alleles (odds ratio [OR] 2.57, recessive model P = 1.49 × 10−9), and after adjustment for age, sex, and ancestry admixture (OR 2.72, P = 6.23 × 10−6). The age-, sex-, and admixture-adjusted population attributable risk for ESRD among patients with G1/G2 polymorphisms was 0.26, compared to 0.003 among European American patients. The mean time from SLE diagnosis to ESRD development was ~2 years earlier among individuals with APOL1 risk genotypes (P = 0.01).
APOL1 G1/G2 alleles strongly impact the risk of LN-ESRD in African Americans, as well as the time to progression to ESRD. The high frequency of these alleles in African Americans with near absence in European Americans explains an important proportion of the increased risk of LN-ESRD in African Americans.
PMCID: PMC4002759  PMID: 24504811
11.  Erythropoiesis-stimulating Agent Use among Patients with Lupus Nephritis Approaching End-stage Renal Disease 
Little is known about erythropoiesis-stimulating agents (ESAs) utilization among lupus nephritis (LN) patients with incipient ESRD. We aimed to identify sociodemographic and clinical factors associated with ESA use among incident LN ESRD patients.
Among all individuals age ≥18 with incident ESRD from 1995-2008 in the U.S. Renal Data System (USRDS), we identified those with systemic lupus erythematosus (ICD-9 code 710.0) as the cause of ESRD. ESA use at ESRD onset was ascertained from the Medical Evidence Report. Year of onset, age, sex, race/ethnicity, medical insurance, employment status, residential region, clinical factors and comorbidities were considered potentially associated with ESA use in multivariable-adjusted logistic regression analyses.
We identified 12,533 individuals with incident LN ESRD (1% of entire population). Of those, 4,288 (34%) received an ESA preceding ESRD. In multivariable-adjusted models, ESA users had higher serum albumin and hemoglobin concentrations, were more likely to be women, and to live in the Northeast. Conversely, Medicaid beneficiaries, the uninsured, unemployed, African Americans, Hispanics, and those with IV drug use, congestive heart failure and obesity had lower ESA use.
Among all U.S. patients and those with LN who developed ESRD, approximately one third received ESAs. Patient sex, race, age, medical insurance, residential region and clinical factors were significantly associated with ESA therapy. While there are no guidelines for ESA use in LN patients approaching ESRD, there has been wide sociodemographic variation, raising questions about ESA prescription practices.
PMCID: PMC3963515  PMID: 24672742
Lupus nephritis; End-stage renal disease; Erythropoiesis-stimulating agents; Anemia; Disparity; Race; Ethnicity; Access to care; Sociodemographic
12.  Predictors of the Rate of Change in Disease Activity over Time in LUMINA, a Multiethnic US Cohort of Patients with Systemic Lupus Erythematosus: LUMINA LXX 
Lupus  2010;19(6):727-733.
The objectives of the present study were (1) to clarify and quantify the relationship between age and disease duration with the rate of change in disease activity over time in patients with systemic lupus erythematosus (SLE) and (2) to explore other possible factors associated with this rate of change. To this end, SLE patients from LUMINA were studied if they had ≥3 visits in which disease activity (Systemic Lupus Activity Measure-Revised or SLAM-R) had been ascertained. Variables associated with the rate (slope) of change in disease activity (obtained by regressing the SLAM-R scores against the length of time from diagnosis to last visit) were examined by univariable and multivariable analyses. Five-hundred forty-two of the 632 patients had ≥3 SLAM-R scores. In multivariable analyses Caucasians exhibited the fastest decline in disease activity; Texan Hispanics exhibited the slowest, trailed by the African Americans. Longer disease duration and HLA-DRB1*1503 positivity were associated with a slower decline whereas a greater number of ACR criteria and abnormal laboratory parameters (white blood cell and platelet counts, hematocrit and serum creatinine) were associated with a faster decline. These findings complement existing knowledge on SLE disease activity and are potentially useful to clinicians managing these patients.
PMCID: PMC3964002  PMID: 20118158
Lupus; disease activity; rate of change; ethnicity; cohort
13.  Mestizos with Systemic Lupus Erythematosus Develop Renal Disease Early while Antimalarials Retard its Appearance: Data from a Latin American Cohort 
Lupus  2013;22(9):899-907.
To assess the predictors of time-to-lupus renal disease in Latin American patients.
SLE patients (n=1480) from GLADEL’s (Grupo Latino Americano De Estudio de Lupus) longitudinal inception cohort were studied. Endpoint was ACR renal criterion development after SLE diagnosis (prevalent cases excluded). Renal disease predictors were examined by univariable and multivariable Cox proportional hazards regression analyses. Antimalarials were considered time-dependent in alternative analyses.
Of the entire cohort, 265 patients (17.9%) developed renal disease after entering the cohort. Of them, 88 (33.2%) developed persistent proteinuria, 44 (16.6%) cellular casts and 133 (50.2%) both; 233 patients (87.9%) were women; mean (± SD) age at diagnosis was 28.0 (11.9) years; 12.8% were African-Latin Americans, 52.5% Mestizos, 34.7% Caucasians (p=0.0016). Mestizo ethnicity (HR 1.61, 95% CI 1.19–2.17), hypertension (HR 3.99, 95% CI 3.02–5.26) and SLEDAI at diagnosis (HR 1.04, 95% CI 1.01–1.06) were associated with a shorter time-to-renal disease occurrence; antimalarial use (HR 0.57, 95% CI 0.43–0.77), older age at onset (HR 0.90, 95% CI 0.85–0.95, for every 5 years) and photosensitivity (HR 0.74, 95% CI 0.56–0.98) were associated with a longer time. Alternative model results were consistent with the antimalarial protective effect (HR 0.70, 95% CI 0.50–0.99).
Our data strongly support the fact that Mestizo patients are at increased risk of developing renal disease early while antimalarials seem to delay the appearance of this SLE manifestation. These data have important implications for the treatment of these patients regardless of their geographic location.
PMCID: PMC3943422  PMID: 23857989
14.  Epidemiology and Sociodemographics of Systemic Lupus Erythematosus and Lupus Nephritis among U.S. Adults with Medicaid Coverage, 2000–2004 
Arthritis and rheumatism  2013;65(3):753-763.
Systemic lupus erythematosus (SLE) and lupus nephritis (LN) disproportionately affect racial/ethnic minorities and lower socioeconomic status (SES) individuals. We investigated the epidemiology and sociodemographics of SLE and LN in the low-income U.S. Medicaid population.
We utilized Medicaid Analytic eXtract data, with billing claims from 47 states and Washington, D.C. for 23.9 million individuals, aged 18–65 years, enrolled in Medicaid for >3 months, 2000–2004. Individuals with SLE (> 3 visits, ICD-9 code 710.0, >30 days apart) and with LN (>2 ICD-9 codes for glomerulonephritis, proteinuria or renal failure) were identified. We calculated SLE and LN prevalence and incidence, stratified by sociodemographic categories, and adjusted for number of American College of Rheumatology (ACR) member rheumatologists and SES using a validated composite of U.S. Census variables.
We identified 34,339 individuals with SLE (prevalence = 143.7/100,000) and 7,388 (21.5%) with LN (prevalence = 30.9/100,000). SLE prevalence was 6 times higher among women, nearly double in African American compared to White women, and highest in the U.S. South. LN prevalence was higher among all racial/ethnic groups compared to Whites. The lowest SES areas had the highest prevalence; areas with the fewest ACR rheumatologists had the lowest. SLE incidence was 23.2/100,000 person-years, and LN incidence was 6.9/100,000 person-years, with similar sociodemographic trends.
In this nationwide Medicaid population, there was sociodemographic variation in SLE and LN prevalence and incidence. Understanding the increased burden of SLE and its complications in this low-income population has implications for resource allocation and access to subspecialty care.
PMCID: PMC3733212  PMID: 23203603
Systemic lupus erythematosus; lupus nephritis; epidemiology; socioeconomic factors; disparities
15.  SNPs in VKORC1 are Risk Factors for Systemic Lupus Erythematosus in Asians 
Arthritis and rheumatism  2013;65(1):211-215.
The increased risk of thrombosis in systemic lupus erythematosus (SLE) may be partially explained by interrelated genetic pathways for thrombosis and SLE. In a case-control analysis, we investigated whether 33 established and novel single nucleotide polymorphisms (SNP) in 20 genes involved in hemostasis pathways that have been associated with deep venous thrombosis in the general population were risk factors for SLE development among Asians.
Patients in the discovery cohort were enrolled in one of two North American SLE cohorts. Patients in the replication cohort were enrolled in one of four Asian or two North American cohorts. SLE cases met American College of Rheumatology classification criteria. We first genotyped 263 Asian SLE and 357 healthy Asian control individuals for 33 SNPs using Luminex multiplex technology in the discovery phase, and then used Taqman and Immunochip assays to examine 5 SNPs in up to an additional 1496 cases and 993 controls in the Replication phase. SLE patients were compared to healthy controls for association with minor alleles in allelic models. Principal components analysis was used to control for intra-Asian ancestry in an analysis of the replication cohort.
Two genetic variants in the gene VKORC1, rs9934438 and rs9923231, were highly significant in both the discovery and replication cohorts: OR(disc) = 2.45 (p=2×10−9), OR(rep) = 1.53 (p=5×10−6) and OR(disc) = 2.40 (p=6×10−9), OR(rep) = 1.53 (p=5×10−6), respectively. These associations were significant in the replication cohort after adjustment for intra-Asian ancestry: rs9934438 OR(adj) = 1.34 (p=0.0029) and rs9923231 OR(adj) = 1.34 (p=0.0032).
Genetic variants in VKORC1, involved in vitamin K reduction and associated with DVT, are associated with SLE development in Asians. These results suggest intersecting genetic pathways for the development of SLE and thrombosis.
PMCID: PMC3670944  PMID: 23124848
systemic lupus erythematosus; single nucleotide polymorphisms; genetic risk factors
16.  Two Independent Functional Risk Haplotypes in TNIP1 are Associated with Systemic Lupus Erythematosus 
Arthritis and rheumatism  2012;64(11):3695-3705.
Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by autoantibody production and altered type I interferon expression. Genetic surveys and genome-wide association studies have identified more than 30 SLE susceptibility genes. One of these genes, TNIP1, encodes the ABIN1 protein. ABIN1 functions in the immune system by restricting the NF-κB signaling. In order to better understand the genetic factors that influence association with SLE in genes that regulate the NF-κB pathway, we analyzed a dense set of genetic markers spanning TNIP1 and TAX1BP1, as well as the TNIP1 homolog, TNIP2, in case-control sets of diverse ethnic origins.
We fine-mapped TNIP1, TNIP2, and TAX1BP1 in a total of 8372 SLE cases and 7492 healthy controls from European-ancestry, African-American, Hispanic, East Asian, and African-American Gullah populations. Levels of TNIP1 mRNA and ABIN1 protein were analyzed using quantitative RT-PCR and Western blotting, respectively, in EBV-transformed human B cell lines.
We found significant associations between genetic variants within TNIP1 and SLE but not in TNIP2 or TAX1BP1. After resequencing and imputation, we identified two independent risk haplotypes within TNIP1 in individuals of European-ancestry that were also present in African-American and Hispanic populations. These risk haplotypes produced lower levels of TNIP1 mRNA and ABIN1 protein suggesting they harbor hypomorphic functional variants that influence susceptibility to SLE by restricting ABIN1 expression.
Our results confirmed the association signals between SLE and TNIP1 variants in multiple populations and provide new insight into the mechanism by which TNIP1 variants may contribute to SLE pathogenesis.
PMCID: PMC3485412  PMID: 22833143
17.  Impact of Genetic Ancestry and Socio-Demographic Status on the Clinical Expression of Systemic Lupus Erythematosus in Amerindian-European Populations 
Arthritis and rheumatism  2012;64(11):3687-3694.
Amerindian-Europeans, Asians and African-Americans have an excess morbidity from SLE and higher prevalence of lupus nephritis than Caucasians. The aim of this study was to analyze the relationship between genetic ancestry and socio-demographic characteristics and clinical features in a large cohort of Amerindian-European SLE patients.
A total of 2116 SLE patients of Amerindian-European origin and 4001 SLE patients of European descent with clinical data were used in the study. Genotyping of 253 continental ancestry informative markers was performed on the Illumina platform. The STRUCTURE and ADMIXTURE software were used to determine genetic ancestry of each individual. Correlation between ancestry and socio-demographic and clinical data were analyzed using logistic regression.
The average Amerindian genetic ancestry of 2116 SLE patients was 40.7%. There was an increased risk of having renal involvement (P<0.0001, OR= 3.50 95%CI 2.63-4.63) and an early age of onset with the presence of Amerindian genetic ancestry (P<0.0001). Amerindian ancestry protected against photosensitivity (P<0.0001, OR= 0.58 95%CI 0.44-0.76), oral ulcers (P<0.0001, OR= 0.55 95%CI 0.42-0.72), and serositis (P<0.0001, OR= 0.56 95%CI 0.41-0.75) after adjustment by age, gender and age of onset. However, gender and age of onset had stronger effects on malar rash, discoid rash, arthritis and neurological involvement than genetic ancestry.
In general, genetic Amerindian ancestry correlates with lower socio-demographic status and increases the risk for developing renal involvement and SLE at an earlier age of onset.
PMCID: PMC3485439  PMID: 22886787
18.  Preferential Binding to Elk-1 by SLE-Associated IL10 Risk Allele Upregulates IL10 Expression 
PLoS Genetics  2013;9(10):e1003870.
Immunoregulatory cytokine interleukin-10 (IL-10) is elevated in sera from patients with systemic lupus erythematosus (SLE) correlating with disease activity. The established association of IL10 with SLE and other autoimmune diseases led us to fine map causal variant(s) and to explore underlying mechanisms. We assessed 19 tag SNPs, covering the IL10 gene cluster including IL19, IL20 and IL24, for association with SLE in 15,533 case and control subjects from four ancestries. The previously reported IL10 variant, rs3024505 located at 1 kb downstream of IL10, exhibited the strongest association signal and was confirmed for association with SLE in European American (EA) (P = 2.7×10−8, OR = 1.30), but not in non-EA ancestries. SNP imputation conducted in EA dataset identified three additional SLE-associated SNPs tagged by rs3024505 (rs3122605, rs3024493 and rs3024495 located at 9.2 kb upstream, intron 3 and 4 of IL10, respectively), and SLE-risk alleles of these SNPs were dose-dependently associated with elevated levels of IL10 mRNA in PBMCs and circulating IL-10 protein in SLE patients and controls. Using nuclear extracts of peripheral blood cells from SLE patients for electrophoretic mobility shift assays, we identified specific binding of transcription factor Elk-1 to oligodeoxynucleotides containing the risk (G) allele of rs3122605, suggesting rs3122605 as the most likely causal variant regulating IL10 expression. Elk-1 is known to be activated by phosphorylation and nuclear localization to induce transcription. Of interest, phosphorylated Elk-1 (p-Elk-1) detected only in nuclear extracts of SLE PBMCs appeared to increase with disease activity. Co-expression levels of p-Elk-1 and IL-10 were elevated in SLE T, B cells and monocytes, associated with increased disease activity in SLE B cells, and were best downregulated by ERK inhibitor. Taken together, our data suggest that preferential binding of activated Elk-1 to the IL10 rs3122605-G allele upregulates IL10 expression and confers increased risk for SLE in European Americans.
Author Summary
Systemic lupus erythematosus (SLE), a debilitating autoimmune disease characterized by the production of pathogenic autoantibodies, has a strong genetic basis. Variants of the IL10 gene, which encodes cytokine interleukin-10 (IL-10) with known function of promoting B cell hyperactivity and autoantibody production, are associated with SLE and other autoimmune diseases, and serum IL-10 levels are elevated in SLE patients correlating with increased disease activity. In this study, to discover SLE-predisposing causal variant(s), we assessed variants within the genomic region containing IL10 and its gene family member IL19, IL20 and IL24 for association with SLE in case and control subjects from diverse ancestries. We identified SLE-associated SNP rs3122605 located at 9.2 kb upstream of IL10 as the most likely causal variant in subjects of European ancestry. The SLE-risk allele of rs3122605 was dose-dependently associated with elevated IL10 expression at both mRNA and protein levels in peripheral blood samples from SLE patients and controls, which could be explained, at least in part, by its preferential binding to Elk-1, a transcription factor activated in B cells during active disease of SLE patients. Elk-1-mediated IL-10 overexpression could be downregulated by inhibiting activation of mitogen-activated protein kinases, suggesting a potential therapeutic target for SLE.
PMCID: PMC3794920  PMID: 24130510
20.  Time to Neuropsychiatric Damage Occurrence in LUMINA: A Multiethnic Lupus Cohort 
Lupus  2009;18(9):822-830.
The aims of this study were to examine the predictors of time-to-neuropsychiatric (NP) damage and its impact on mortality in 632 systemic lupus erythematosus (SLE) African American, Hispanic and Caucasian LUMINA patients, age ≥ 16 years and disease duration ≤ 5 years at baseline (T0). Time-to-NP damage and its impact on mortality were examined by Cox proportional hazards regressions. One-hundred eighty-five (29.3%) patients developed NP-damage over a mean (SD) disease duration of 5.6 (3.7) years. After adjusting for neuropsychiatric manifestations present, older age [Hazard ratio (HR)=1.02; 95% [Confidence interval (CI) 1.00–1.04)], Caucasian ethnicity (HR=1.87; 95% CI 1.22-2.87), disease activity over the disease course (HR=1.16; 95% CI 1.12–1.21), diabetes (HR=3.47; 95% CI 1.44–8.38) and abnormal illness-related behaviors (HR=1.05; 95% CI 1.02–1.08) were associated with a shorter time to NP-damage. Photosensitivity (HR=0.65; 95% CI 0.44–0.95), anemia (HR=0.56; 95% CI 0.31–0.98), Raynaud’s phenomenon (HR=0.49; 95% CI 0.34–0.72), a medium dose of prednisone (HR=0.56; 95% CI 0.35–0.92) and hydroxychloroquine use (HR=0.58; 95% CI 0.36–0.93) were associated with a longer time. NP-damage did not contribute to mortality. Older age, Caucasian ethnicity, disease activity and abnormal illness-related behaviors are associated with a shorter time-to-NP damage; hydroxychloroquine and a medium dose of prednisone with a longer time.
PMCID: PMC3759150  PMID: 19578107
21.  The Impact of Rural Residency on the Expression and Outcome of Systemic Lupus Erythematosus: Data From a Multiethnic Latin American Cohort 
Lupus  2012;21(13):1397-1404.
To examine the role of place of residency in the expression and outcomes of SLE in a multi-ethnic Latin American cohort.
Patients and Methods
SLE patients (<2 years of diagnosis) from 34 centers constitute this cohort. Residency was dichotomized into rural and urban, cut-off: 10,000 inhabitants. Socio-demographic, clinical/laboratory, and mortality rates were compared between them using descriptive tests. The influence of place of residency on disease activity at diagnosis and renal disease was examined by multivariable regression analyses.
122 (8.6%) of 1426 patients were rural residents. Their median age (onset, diagnosis) were 23.5 and 25.5 years; 85 (69.7%) patients were Mestizos, 28 (22.9%) Caucasians and 9 (7.4%) African-Latin Americans. Rural residents were more frequently younger at diagnosis, Mestizo and uninsured; they also had fewer years of education and a lower socioeconomic status, exhibited hypertension and renal disease more frequently, and had higher levels of disease activity at diagnosis; they used methotrexate, cyclophosphamide pulses, and hemodialysis more frequently than urban patients. Disease activity over time, renal damage, overall damage and the proportion of deceased patients were comparable in both, rural and urban patients.. In multivariable analyses, rural residency was associated with high levels of disease activity at diagnosis (OR 1.65, 95% CI 1.06–2.57) and renal disease occurrence (OR 1.77, 95% CI 1.00–3.11).
Rural residency associates with Mestizo ethnicity, lower socioeconomic status, and renal disease occurrence. It also plays a role on disease activity at diagnosis and kidney involvement but not on the other end-points examined.
PMCID: PMC3758687  PMID: 22941567
22.  Peripheral Vascular Damage in Systemic Lupus Erythematosus: Data from LUMINA, a Large Multiethnic Cohort 
Lupus  2009;18(14):1303-1308.
To determine the factors associated with peripheral vascular damage in systemic lupus erythematosus (SLE) patients and its impact on survival from LUMINA, a longitudinal multiethnic cohort. Peripheral vascular damage was defined by the Systemic Lupus International Collaborating Clinics (SLICC) Damage Index (SDI). Factors associated with peripheral vascular damage were examined by univariable and multivariable logistic regression models and its impact on survival by a Cox multivariable regression. Thirty-four (5.3%) of 637 patients (90% women, mean [SD] age 36.5 [12.6] (16-87) years developed peripheral vascular damage. Age and the SDI (without peripheral vascular damage) were statistically significant (odds ratio [OR] =1.05, 95% confidence interval [CI] 1.01-1.08; p=0.0107 and OR=1.30, 95% CI 0.09-1.56; p=0.0043, respectively) in multivariable analyses. Azathioprine, warfarin and statins were also statistically significant, glucocorticoid use was borderline statistically significant (OR=1.03, 95% CI 0.10-1.06; p=0.0975). In the survival analysis, peripheral vascular damage was independenly associated with a diminished survival (Hazard Ratio =2.36; 95% CI 1.07-5.19; p=0.0334). In short, age was independently associated with peripheral vascular damage, but so was the presence of damage in others organs (ocular, neuropsychiatric, renal, cardiovascular, pulmonary, musculoskeletal and integument) and some medications (probably reflecting more severe disease). Peripheral vascular damage also negatively affected survival.
PMCID: PMC3758688  PMID: 19850658
23.  PTPN22 Association in Systemic Lupus Erythematosus (SLE) with Respect to Individual Ancestry and Clinical Sub-Phenotypes 
PLoS ONE  2013;8(8):e69404.
Protein tyrosine phosphatase non-receptor type 22 (PTPN22) is a negative regulator of T-cell activation associated with several autoimmune diseases, including systemic lupus erythematosus (SLE). Missense rs2476601 is associated with SLE in individuals with European ancestry. Since the rs2476601 risk allele frequency differs dramatically across ethnicities, we assessed robustness of PTPN22 association with SLE and its clinical sub-phenotypes across four ethnically diverse populations. Ten SNPs were genotyped in 8220 SLE cases and 7369 controls from in European-Americans (EA), African-Americans (AA), Asians (AS), and Hispanics (HS). We performed imputation-based association followed by conditional analysis to identify independent associations. Significantly associated SNPs were tested for association with SLE clinical sub-phenotypes, including autoantibody profiles. Multiple testing was accounted for by using false discovery rate. We successfully imputed and tested allelic association for 107 SNPs within the PTPN22 region and detected evidence of ethnic-specific associations from EA and HS. In EA, the strongest association was at rs2476601 (P = 4.7×10−9, OR = 1.40 (95% CI = 1.25–1.56)). Independent association with rs1217414 was also observed in EA, and both SNPs are correlated with increased European ancestry. For HS imputed intronic SNP, rs3765598, predicted to be a cis-eQTL, was associated (P = 0.007, OR = 0.79 and 95% CI = 0.67–0.94). No significant associations were observed in AA or AS. Case-only analysis using lupus-related clinical criteria revealed differences between EA SLE patients positive for moderate to high titers of IgG anti-cardiolipin (aCL IgG >20) versus negative aCL IgG at rs2476601 (P = 0.012, OR = 1.65). Association was reinforced when these cases were compared to controls (P = 2.7×10−5, OR = 2.11). Our results validate that rs2476601 is the most significantly associated SNP in individuals with European ancestry. Additionally, rs1217414 and rs3765598 may be associated with SLE. Further studies are required to confirm the involvement of rs2476601 with aCL IgG.
PMCID: PMC3737240  PMID: 23950893
24.  Variable association of reactive intermediate genes with systemic lupus erythematosus (SLE) in populations with different African ancestry 
The Journal of rheumatology  2013;40(6):842-849.
Little is known about the genetic etiology of systemic lupus erythematosus (SLE) in individuals of African ancestry, despite its higher prevalence and greater disease severity. Overproduction of nitric oxide (NO) and reactive oxygen species are implicated in the pathogenesis and severity of SLE, making NO synthases and other reactive intermediate related genes biological candidates for disease susceptibility. This study analyzed variation in reactive intermediate genes for association with SLE in two populations with African ancestry.
A total of 244 SNPs from 53 regions were analyzed in non-Gullah African Americans (AA; 1432 cases and 1687 controls) and the genetically more homogeneous Gullah of the Sea Islands of South Carolina (133 cases and 112 controls) and. Single-marker, haplotype, and two-locus interaction tests were computed for these populations.
The glutathione reductase gene GSR (rs2253409, P=0.0014, OR [95% CI]=1.26 [1.09–1.44]) was the most significant single-SNP association in AA. In the Gullah, the NADH dehydrogenase NDUFS4 (rs381575, P=0.0065, OR [95%CI]=2.10 [1.23–3.59]) and nitric oxide synthase gene NOS1 (rs561712, P=0.0072, OR [95%CI]=0.62 [0.44–0.88]) were most strongly associated with SLE. When both populations were analyzed together, GSR remained the most significant effect (rs2253409, P=0.00072, OR [95%CI]=1.26 [1.10–1.44]). Haplotype and two-locus interaction analyses also uncovered different loci in each population.
These results suggest distinct patterns of association with SLE in African-derived populations; specific loci may be more strongly associated within select population groups.
PMCID: PMC3735344  PMID: 23637325
systemic lupus erythematosus; African Americans; genetic association studies; oxygen compounds; single nucleotide polymorphism
25.  Derivation and Validation of Systemic Lupus International Collaborating Clinics Classification Criteria for Systemic Lupus Erythematosus 
Arthritis and rheumatism  2012;64(8):2677-2686.
The Systemic Lupus Collaborating Clinics (SLICC) revised and validated the American College of Rheumatology (ACR) SLE classification criteria in order to improve clinical relevance, meet stringent methodology requirements and incorporate new knowledge in SLE immunology.
The classification criteria were derived from a set of 702 expert-rated patient scenarios. Recursive partitioning was used to derive an initial rule that was simplified and refined based on SLICC physician consensus. SLICC validated the classification criteria in a new validation sample of 690 SLE patients and controls.
Seventeen criteria were identified. The SLICC criteria for SLE classification requires: 1) Fulfillment of at least four criteria, with at least one clinical criterion AND one immunologic criterion OR 2) Lupus nephritis as the sole clinical criterion in the presence of ANA or anti-dsDNA antibodies. In the derivation set, the SLICC classification criteria resulted in fewer misclassifications than the current ACR classification criteria (49 versus 70, p=0.0082), had greater sensitivity (94% versus 86%, p<0.0001) and equal specificity (92% versus 93%, p=0.39). In the validation set, the SLICC Classification criteria resulted in fewer misclassifications (62 versus 74, p=0.24), had greater sensitivity (97% versus 83%, p<0.0001) but less specificity (84% versus 96%, p<0.0001).
The new SLICC classification criteria performed well on a large set of patient scenarios rated by experts. They require that at least one clinical criterion and one immunologic criterion be present for a classification of SLE. Biopsy confirmed nephritis compatible with lupus (in the presence of SLE autoantibodies) is sufficient for classification.
PMCID: PMC3409311  PMID: 22553077

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