Blood immunophenotyping identifies distinct kidney histopathology and outcomes in patients with lupus nephritis

Lupus nephritis (LN) is a frequent manifestation of systemic lupus erythematosus, and fewer than half of patients achieve complete renal response with standard immunosuppressants. Identifying non-invasive, blood-based pathologic immune alterations associated with renal injury could aid therapeutic decisions. Here, we used mass cytometry immunophenotyping of peripheral blood mononuclear cells in 145 patients with biopsy-proven LN and 40 healthy controls to evaluate the heterogeneity of immune activation in patients with LN and to identify correlates of renal parameters and treatment response. Unbiased analysis identified 3 immunologically distinct groups of patients with LN that were associated with different patterns of histopathology, renal cell infiltrates, urine proteomic profiles, and treatment response at one year. Patients with enriched circulating granzyme B+ T cells at baseline showed more severe disease and increased numbers of activated CD8 T cells in the kidney, yet they had the highest likelihood of treatment response. A second group characterized primarily by a high type I interferon signature had a lower likelihood of response to therapy, while a third group appeared immunologically inactive by immunophenotyping at enrollment but with chronic renal injuries. Main immune profiles could be distilled down to 5 simple cytometric parameters that recapitulate several of the associations, highlighting the potential for blood immune profiling to translate to clinically useful non-invasive metrics to assess immune-mediated disease in LN.

Urine proteomic signatures of histological class, activity, chronicity, and treatment response in lupus nephritis

Lupus nephritis (LN) is a pathologically heterogenous autoimmune disease linked to end-stage kidney disease and mortality. Better therapeutic strategies are needed as only 30%-40% of patients completely respond to treatment. Noninvasive biomarkers of intrarenal inflammation may guide more precise approaches. Because urine collects the byproducts of kidney inflammation, we studied the urine proteomic profiles of 225 patients with LN (573 samples) in the longitudinal Accelerating Medicines Partnership in RA/SLE cohort. Urinary biomarkers of monocyte/neutrophil degranulation (i.e., PR3, S100A8, azurocidin, catalase, cathepsins, MMP8), macrophage activation (i.e., CD163, CD206, galectin-1), wound healing/matrix degradation (i.e., nidogen-1, decorin), and IL-16 characterized the aggressive proliferative LN classes and significantly correlated with histological activity. A decline of these biomarkers after 3 months of treatment predicted the 1-year response more robustly than proteinuria, the standard of care (AUC: CD206 0.91, EGFR 0.9, CD163 0.89, proteinuria 0.8). Candidate biomarkers were validated and provide potentially treatable targets. We propose these biomarkers of intrarenal immunological activity as noninvasive tools to diagnose LN and guide treatment and as surrogate endpoints for clinical trials. These findings provide insights into the processes involved in LN activity. This data set is a public resource to generate and test hypotheses and validate biomarkers.

A genome-wide association study suggests new susceptibility loci for primary antiphospholipid syndrome

Objectives

Primary antiphospholipid syndrome (PAPS) is a rare autoimmune disease characterized by the presence of antiphospholipid antibodies and the occurrence of thrombotic events and pregnancy complications. Our study aimed to identify novel genetic susceptibility loci associated with PAPS.

Methods

We performed a genome-wide association study comprising 5,485 individuals (482 affected individuals) of European ancestry. Significant and suggestive independent variants from a meta-analysis of approximately 7 million variants were evaluated for functional and biological process enrichment. The genetic risk variability for PAPS in different populations was also assessed. Hierarchical clustering, Mahalanobis distance, and Dirichlet Process Mixtures with uncertainty clustering methods were used to assess genetic similarities between PAPS and other immune-mediated diseases.

Results

We revealed genetic associations with PAPS in a regulatory locus within the HLA class II region near HLA-DRA and in STAT4 with a genome-wide level of significance. 34 additional suggestive genetic susceptibility loci for PAPS were also identified. The disease risk allele in the HLA class II locus is associated with overexpression of HLA-DRB6 , HLA-DRB9 , HLA-DPB2 , HLA-DQA2 and HLA-DQB2 , and is independent of the association between PAPS and HLA-DRB1*1302 . Functional analyses highlighted immune and nervous system related pathways in PAPS-associated loci. The comparison with other immune-mediated diseases revealed a close genetic relatedness to neuromyelitis optica, systemic sclerosis, and Sjögren's syndrome, suggesting colocalized causal variations close to STAT4 , TNPO3 , and BLK .

Conclusions

This study represents a comprehensive large-scale genetic analysis for PAPS and provides new insights into the genetic basis and pathophysiology of this rare disease.

Obexelimab in Systemic Lupus Erythematosus With Exploration of Response Based on Gene Pathway Co-Expression Patterns: A Double-Blind, Randomized, Placebo-Controlled, Phase 2 Trial

OBJECTIVE

Obexelimab is an investigational, bifunctional, noncytolytic monoclonal antibody that binds CD19 and FcyRIIb to inhibit B cells, plasmablasts, and plasma cells. This trial evaluated the efficacy and safety of obexelimab in the treatment of patients with systemic lupus erythematosus (SLE).

METHODS

During screening, patients with active, non-organ-threatening SLE received corticosteroid injections to ameliorate symptoms while immunosuppressants were withdrawn (≤10 mg/day prednisone equivalent and ≤400 mg/day hydroxychloroquine allowed). Patients with improved disease activity were randomized 1:1 to obexelimab 5 mg/kg intravenously or placebo once every 2 weeks until week 32 or loss of improvement (LOI).

RESULTS

In this study, 104 patients were randomized. Analysis of the primary endpoint, proportion of patients reaching week 32 without LOI, used an efficacy-evaluable (EE) population defined as patients who completed the study or withdrew for flare or treatment-related toxicity. This endpoint did not reach statistical significance: 21 of 50 obexelimab-treated patients (42.0%) versus 12 of 42 patients (28.6%) treated with a placebo (P = 0.183). Time to LOI was increased in obexelimab-treated patients versus patients treated with a placebo in the EE (hazard ratio [HR] 0.53, P = 0.025) and intention-to-treat (HR 0.59, P = 0.062) populations. In obexelimab-treated patients, B cells decreased approximately 50%, and trough concentration and inclusion in baseline gene expression clusters with high B cell pathway modules were associated with increased time to LOI. Obexelimab was associated with infusion reactions but was generally safe and well-tolerated.

CONCLUSION

Although the primary endpoint was not reached, secondary analysis showed time to LOI was significantly increased in obexelimab-treated patients, and analysis of patient subsets defined by gene expression patterns at baseline suggests a responding subpopulation.

POS0098 LINC01871, IMPLICATED IN SJÖGREN’S DISEASE PATHOGENESIS, IS REGULATED BY INTERFERON-G AND CALCINEURIN SIGNALING

Background

Sjögren’s disease (SjD) is an autoimmune disease characterized by exocrine gland dysfunction. Long non-coding RNAs (lncRNAs) are a functionally diverse class of non-protein coding RNAs that are longer than 200 nucleotides. Our previous study using whole blood RNA-seq found that lncRNA, LINC01871, is overexpressed in SjD relative to controls [1]. CRISPR-Cas9 targeting in HSB2 T cells yielded a LINC01871-/- clone with altered expression of many genes implicated in immune regulation [1].

Objectives

The goal of this study was to analyze the gene expression perturbations resulting from the loss of LINC01871 and to characterize the regulation of LINC01871 in both the LINC01871-/- clone and primary human T cells in response to immune stimuli.

Methods

Flow cytometry and LegendPlex bead assays were used to compare surface and secreted protein expression changes, respectively, in LINC01871-/- cells and the parental HSB2 cells. Parental HSB2 T cells, LINC01871-/- cells, Kasumi-3 myeloid cells, and primary human T cells were stimulated in vitro and changes in gene expression were measured over time using qRT-PCR. Responses to interferons (IFN) were assessed using universal type I IFN (IFNα) or IFNγ. TCR signaling responses were assessed using PMA/Ionomycin (PMA/I) or anti-CD3/CD28 stimulations in the presence or absence of the calcineurin inhibitor, FK506.

Results

Previous RNA-seq analysis found 1166 differentially expressed (DE) transcripts (log2FC ≥1 or ≤-1; padj ≤0.05) in LINC01871-/- cells compared to parental HSB2 cells, including many prominent immune regulatory genes. Changes in the basal expression of 7 proteins in LINC01871-/- cells were confirmed using flow cytometry (significantly decreased: CD8a (p=0.0004), CD30 (p=0.0008), CXCR3 (p=0.037), T-Bet (p=0.0002), and Aiolos (p=0.02); significantly increased: CD226 (p=0.0059) and CD44 (p=0.024)). Analysis of LINC01871-/- cells revealed a growth inhibition in LINC01871-/- cells (p=0.0014 at 72h), in which multiple secreted growth and adhesion factors were significantly reduced: GM-CSF (p=2.0e-06), M-CSF (p=2.7e-09), IGBPF4 (p=1.2e-07), s-ICAM1 (p=0.015), MMP9 (p=3.0e-14), and MMP2 (p=6e-08). In contrast, the IL-6 cytokine family member, LIF, was significantly increased in LINC01871-/- cells (p=1.2e-07). Because HSB2 cells were not responsive to all IFNs, IFN-mediated regulation of LINC01871 expression was examined in the Kasumi-3 myeloid cell line. While LINC01871 expression was not modulated by type I IFN stimulation, it was robustly responsive to IFNγ treatment. Since LINC01871 was expressed in T cells and implicated in T cell pathways, responses to TCR signaling pathways were characterized in HSB2 cells or purified primary human T cells treated with PMA/I. In both cell types, LINC01871 exhibited a prolonged decrease in expression that was abrogated by concurrent treatment with FK506, indicating that LINC01871 is regulated by calcineurin signaling. Treatment of primary human T cells with anti-CD3/CD28 to mimic true TCR engagement resulted in a modest decrease of LINC01871 expression at early time points, followed by an increase in expression with longer stimulation (2d).

Conclusion

Our findings suggest that LINC01871 is a potential mediator of the dysregulated T cell inflammatory response pathways implicated in SjD pathogenesis. LINC01871 influences the expression of many important immune cell genes and growth factors, is inducible by IFNγ, and is regulated directly by calcineurin signaling and TCR ligand engagement. Although LINC01871 functions are still unknown, observed LINC01871 overexpression in whole blood of SjD cases and after prolonged TCR stimulation in primary human T cells suggests that it could be a biomarker of SjD.

References

[1]Joachims, et al. Annals of the Rheumatic Diseases 2020;79:90.

Disclosure of Interests

Michelle L Joachims: None declared, Bhuwan Khatri: None declared, Chuang Li: None declared, Kandice L Tessneer: None declared, John Ice: None declared, Anna M Stolarczyk: None declared, Nicolas Means: None declared, Kiely Grundahl: None declared, Stuart Glenn: None declared, Jennifer Kelly: None declared, David Lewis: None declared, Lida Radfar: None declared, Donald Stone: None declared, Joel Guthridge: None declared, Judith A. James: None declared, R Hal Scofield: None declared, Graham B Wiley: None declared, Jonathan Wren: None declared, Patrick M Gaffney: None declared, Courtney Montgomery: None declared, Kathy Sivils Employee of: Current employee of Janssen., Astrid Rasmussen: None declared, A Darise Farris: None declared, Indra Adrianto: None declared, Christopher Lessard: None declared

AB0026 CELL TYPE-SPECIFIC DYSREGULATION FOUND TO DIFFERENTIATE PATIENT SUBSETS OF SJÖGREN’S DISEASE

Background

Sjögren’s disease (SjD) is a chronic, heterogenous autoimmune disorder characterized by inflammatory destruction of the exocrine glands and Ro autoantibodies. Previous studies, most in whole blood, reported transcriptional and cell type differences between SjD subphenotypes.

Objectives

Evaluate the role of cell type-specific dysregulation in subpopulations of SjD patients having focal lymphocytic sialadenitis and/or anti-Ro/SSA and/or ANA positivity using single-cell RNA-seq (scRNA-seq).

Methods

Peripherical blood mononuclear cells (PBMCs) stored at -120°C from 30 SjD patients and 10 healthy controls (HCs) were selected from our OMRF Sjögren’s Research Cohort based on ACR/EULAR 2016 criteria. PBMCs were captured, libraries processed using 10X Genomics Chromium v3.1 and sequenced to a depth of ~45,000 reads/cell. 10X Genomics Cell Ranger (v 6.1.2) cell multiplexing pipeline was used to align reads to the GRCh38 human genome and separate combined data to per-sample output files. Seurat R package was used for quality control (QC), integration, clustering, and cell type assignment. Differential expression (DE) analysis was done using Seurat for genes with 10% or more of the cells showing expression. DE transcripts (defined as padj<0.05) were evaluated using Ingenuity Pathway Analysis (IPA).

Results

After removing cells with low feature counts, high mitochondrial gene counts, and/or other QC criteria, a total of 331,981 cells were captured. Cells were mapped to 28 clusters using Seurat, then cell types were predicted using marker genes developed from an in-house reference panel of publicly available scRNA-seq datasets. Mapping condensed the 28 observed cell clusters to 19 clusters of specific cell types; 4 clusters remained unidentified. Percentages of each cell type were compared across various subsets of SjD (Ro+; Ro-; Ro-/ANA+; Ro-/ANA-) and HCs. CD14 monocytes were decreased in Ro-/ANA- vs. Ro+ or Ro-/ANA+ cases (p<0.05) and trended downward when compared to HCs (p=0.057). CD8 central memory T cells (TCM) were decreased in Ro+ vs. Ro- or Ro-/ANA- cases (p<0.02) and trended downward when vs. HCs (p=0.076). Conventional dendric cells (DCs) were increased in Ro+ vs. Ro-/ANA- SjD cases (p=0.036) and trended upward in Ro+ vs. Ro- cases (p=0.08) but were not significantly different from HCs. Natural killer (NK) cells were increased in both Ro-/ANA- and Ro- vs. Ro+ (p<0.05).

DE analysis between immune cell subsets revealed potential subphenotype-specific differences in pathophysiology. Interferon signaling was upregulated in CD14 monocytes, naïve B, and CD4 central memory (TCM) cells from the Ro+ subset. Ro+ subset also showed upregulation of genes involved in T cell receptor signaling in CD4 cytotoxic T (CTL), CD4 TCM, and CD4 effector memory T (TEM) cells, but downregulation of this pathway in CD8 TCM cells. Ro+ subset also exhibited increased B cell receptor signaling pathway in naïve and memory B cells. Ro+ subset showed downregulation of autophagy in naïve B, CD4 CTL, CD4 TCM, and CD4 TEM cells. Several cell types in Ro+ and Ro-(ANA+/-) subsets showed decreased DE of genes involved in nitric oxide production and NRF2 oxidative stress pathways. Ro- (ANA+/-) vs. HCs showed increased IL6 and TREM1 signaling pathways in CD14 and CD16 monocytes. While Ro+ subsets showed upregulation of B and T cell pathways (shown previously in lupus), Ro- (ANA+/-) showed dysregulation of osteoarthritis and neuroinflammatory pathways. Interestingly, among the DE long intergenic non-coding (linc)RNAs found herein, we observed that LINC01871, which we previously reported as DE in all subsets of SjD, was overexpressed in CD4 CTL and NK cells in both Ro+ and Ro- (ANA-) vs. HCs.

Conclusion

This interim analysis shows similarities and differences in the dysregulation of genes and pathways for specific cell subsets from our Ro+ and Ro- (ANA+/-) subsets of SjD, potentially allowing for more tailored diagnostics and interventions for the disease in the future.

Disclosure of Interests

Chuang Li: None declared, Bhuwan Khatri: None declared, Anna M Stolarczyk: None declared, Kandice L Tessneer: None declared, Astrid Rasmussen: None declared, Joel Guthridge: None declared, Judith A. James: None declared, R Hal Scofield: None declared, He Li Employee of: Current employee of Janssen, A Darise Farris Grant/research support from: Active collaborative research agreement with Janssen, Kathy Sivils Employee of: Current employee of Janssen, Christopher Lessard Grant/research support from: Active collaborative research agreement with Janssen

Quantifying Chemical Composition and Reaction Kinetics of Individual Colloidally Dispersed Nanoparticles

To control a nanoparticle's chemical composition and thus function, researchers require readily accessible and economical characterization methods that provide quantitative in situ analysis of individual nanoparticles with high throughput. Here, we established dual analyte single-particle inductively coupled plasma quadrupole mass spectrometry to quantify the chemical composition and reaction kinetics of individual colloidal nanoparticles. We determined the individual bimetallic nanoparticle mass and chemical composition changes during two different chemical reactions: (i) nanoparticle etching and (ii) element deposition on nanoparticles at a rate of 300+ nanoparticles/min. Our results revealed the heterogeneity of chemical reactions at the single nanoparticle level. This proof-of-concept study serves as a framework to quantitatively understand the dynamic changes of physicochemical properties that individual nanoparticles undergo during chemical reactions using a commonly available mass spectrometer. Such methods will broadly empower and inform the synthesis and development of safer, more effective, and more efficient nanotechnologies that use nanoparticles with defined functions.

ARID3a Defines a Novel Subset of Naïve B Cells in SLE Patients

Systemic Lupus Erythematosus (SLE) is a complex autoimmune disease characterized by overproduction of autoantibodies by B cells and the loss of tolerance to nucleic acids. Our previous studies show that AT-rich interacting domain 3a (ARID3a), a DNA-binding protein, is more abundant in SLE B cells than in healthy control B cells. Increased numbers of ARID3a+ B cells in SLE correlated with increased disease activity in patients. ARID3a expression in SLE patient blood occurred in naïve B cell subsets which do not express ARID3a in healthy controls. Studies by the Sanz laboratory revealed that activated naïve B cells and may be precursors for the double negative (DN) B cells linked to pathogenic responses in SLE. We hypothesize that ARID3a expression in naïve B cells also defines precursors of pathogenic B cells. In individual patients, ARID3a is bimodally expressed, such that only a fraction of the naïve B cells express ARID3a at any given time. We took advantage of this bimodal expression using single cell technology to perform RNA-seq analyses of ARID3a+ and ARID3a− SLE B cells to identify differentially expressed genes associated with ARID3a. PCA analyses of scRNA seq data show that ARID3a+ naïve B cells cluster together and away from ARID3a− cells. This allows for analyses within and among individual samples by binning cells based on ARID3a expression. Preliminary data indicate that ARID3a expression is correlated with innate immune response genes, transcription factors, and epigenetic regulators. These studies will be informative regarding how ARID3a expression contributes to disease pathogenesis in patients with SLE and will provide novel information defining a new subset of naive B cells that may be directly linked to breaches in tolerance.

AB006. A modular analysis approach to studying gene expression in cutaneous lupus erythematosus

Previous studies on blood transcription profiles of patients with cutaneous lupus (CLE) have primarily used a gene expression approach. The large amount of data involved in these studies can make data analysis and interpretation cumbersome. Consequently, a novel approach in gene expression analyses was devised that groups genes into transcriptional modules (i.e., apoptosis, protein synthesis, inflammation) to identify important themes and relevant genes. This approach was used to study gene expression in systemic lupus patients and subsequently identified a unique interferon signature. Thus, we aim to use the modular analysis approach to identify unique modules and genes of CLE patients in order to better understand their disease pathophysiology. We conducted RNA sequencing of whole transcriptomes of blood from 66 CLE patients and 10 human controls and subsequently performed modular analyses. Based on module scores, we performed an unsupervised cluster analysis to identify subgroups of CLE patients with distinct gene expression patterns. Statistical analyses comparing module scores of these clusters was performed using the Kruskal-Wallis tests with Bonferroni’s correction. Modules were associated with patient subgroups distinguished by demographic, clinical, and laboratory features such as CLE subtypes, autoantibody profiles (BioPlex^® 2200 ANA Screen with MDSS), and cytokine profiles (Thermo Scientific ProCarta xMAP cytokine assay kits). The unsupervised cluster analysis identified eight distinct clusters of CLE patients and controls. A neutrophilic predominant signature governed by azurophilic granule genes (i.e., BPI, LTF, MPO) and neutrophil chemotaxis genes (CEACAM6, CEACAM8) was seen in two groups of patients mostly with subacute lupus erythematosus (SCLE) [n=7 (77.8% of total SCLE)] or lupus erythematosus tumidus (LET) [n=6 (60% of total LET)] and European-American descent [n=28 (53.6% of total European-Americans)]. Four groups consisting of a majority of discoid lupus erythematosus (DLE) patients [n=29 (60% of total DLE)] had a predominant T cell signature driven by genes important for antigen presentation and T cell proliferation and differentiation (i.e., SKAP1, ITK). Our data suggests that unique cell populations may help differentiate CLE subgroups, which can potentially affect their disease course and treatment selection. Further studies examining individual gene and protein levels are necessary to confirm our hypotheses.

OP0140 DYSREGULATED EXPRESSION OF THE LONG NON-CODING RNA, LINC01871, IMPLICATED IN SJÖGREN’S SYNDROME PATHOGENESIS

Background:

Sjögren’s syndrome (SS) is a chronic, heterogenous autoimmune disease characterized by inflammatory destruction of the exocrine glands. Long non-coding RNAs (lncRNAs) have emerged as a functionally diverse class of non-protein coding RNA (ncRNA) with increasing implications in interferon signaling, immune cell regulation, and autoimmune disease pathology. The potential role of lncRNAs in SS pathogenesis is unknown.

Objectives:

To identify and characterize candidate lncRNAs with potential relevance to SS pathology.

Methods:

RNA-seq was used on whole blood from SS patients (n=30 antibody negative (Ro-); n=27 antibody positive (Ro+)) and healthy controls (HC, n=27) to identify differentially expressed (DE) lncRNAs (log2 fold change (FC) ≥ 2 or ≤ 0.5; padj<0.05). Bioinformatic and pathway analyses were used to predict lncRNA function.In vitrotime course experiments in HSB2 T cell lymphoblasts stimulated with PMA/Ionomycin (PMA/I) or type I interferon (IFN) were used to assess biological relevance.LINC01871function was further investigated by RNA-seq on a single cell clone of HSB2 with confirmed CRISPR-targetedLINC01871deletion (LINC01871-/-).

Results:

We identified a total of 1054 unique DE ncRNAs between Ro+, Ro-and/or a combined analysis relative to HC; of these, 45 (1 long intergenic ncRNA (lincRNA), 1 antisense, 43 pseudogenes) were overexpressed in all 3 SS subsets. To begin investigating the function of the previously undescribed lincRNA,LINC01871(SSRo-: FC=2.85; padj=1.1x10-4), we performed a correlation analysis of the SSRo-transcriptome, which found several co-expressed protein coding RNAs involved in immune regulation (THEMIS,TBX21,IL10RA,IL2RB,among many others). Similarly, Ingenuity Pathway Analysis of the SS transcriptome compared to HC, as well as several gene ontology enrichment analyses of publicly available RNA expression correlation databases, identified shared immune-related pathways including cytotoxic T cell, natural killer cell, and T cell regulation. To further study the role ofLINC01871in cytotoxic T cells, we used qRT-PCR to resolve the effects of PMA/I or type I IFN stimulation onLINC01871expression in the T lymphoblastoid HSB2 cells.LINC01871expression was downregulated after PMA/I stimulation, but unchanged with type I IFN stimulation. To explore the regulatory function ofLINC01871in T cells, we targetedLINC01871in HSB2 cells using CRISPR. To this end, we generated a single cellLINC01871-/-clone with no RNA expression by qPCR and confirmed homozygous deletion using DNA sequencing. RNA-seq analysis ofLINC01871-/-compared to unmodified HSB2 cells identified 1166 DE transcripts. Pathway analyses clustered the DE transcripts into similar immune regulatory, cytotoxic and T cell pathways identified in SSRo-whole blood RNA-seq and publicly available RNA-seq databases. Further, several prominent T cell regulatory transcripts that exhibited correlated upregulation withLINC01871in SSRo-whole blood RNA-seq also demonstrated downregulation afterLINC01871deletion:CD109(FC=-9.7; padj=5.3x10-16),IL22(FC=-8.1; padj=7.6x10-11),PDCD1(FC=-6.2; padj=1.1x10-6),THEMIS(FC=-3.8; padj=2.7x10-165) andTBX21(FC=-2.1; padj=3.3x10-25).

Conclusion:

LncRNAs are emerging as important regulators of immune function with increasing evidence of autoimmune disease relevance. Here, we leveraged RNA-seq, extensive bioinformatic data, and CRISPR technology to identify and functionally characterizeLINC01871as a potential mediator of the dysregulated T cell inflammatory response pathways implicated in SS pathogenesis.

Disclosure of Interests:

Michelle L Joachims: None declared, Bhuwan Khatri: None declared, Kandice L Tessneer: None declared, Anna M Stolarczyk: None declared, Graham B Wiley: None declared, Astrid Rasmussen Speakers bureau: Novartis, ThermoFischer, Joel Guthridge Grant/research support from: Xencor, Bristol Myers Squibb, DXterity, Judith A. James Grant/research support from: Progentec Diagnostics, Inc, Consultant of: Abbvie, Novartis, Jannsen, R Hal Scofield Grant/research support from: Pfizer, Kathy L Sivils: None declared, Indra Adrianto: None declared, Christopher Lessard: None declared

SAT0187 DISCRIMINATION OF SYSTEMIC LUPUS (SLE) PATIENTS WITH CLINICAL RESPONSE TO OBEXELIMAB (XMAB®5871) BASED ON A PATTERN OF IMMUNOLOGIC MARKERS

Background:

We recently reported Phase 2 SLE trial results of obexelimab, an FcγRIIb agonist (suppressor of B cell activation). Obexelimab did not meet the primary endpoint (% of patients without flare at Day 225) (p=0.183) but other endpoints such as time to flare (p=0.025) were met.

Objectives:

1. To assign SLE patients to phenotypic subsets based on patterns of gene expression in immune-related pathways.12. To explore the association of immune patterns and clinical response to obexelimab.

Methods:

This analysis included 71 of the 104 participants in the obexelimab study, those who either completed the protocol or terminated for disease flare, if there were adequate blood samples (biomarker subset). At screening, patients were assigned to clusters based on 41 SLE co-expression signature modules from the Human Immune Phenotyping Consortium via unsupervised random forest and K-means clustering.2Other markers of SLE disease were also examined. TheBOLD3study design mandated withdrawal of background immunosuppressants, supporting less ambiguous pharmacodynamic analysis as the trial progressed.

Results:

Immune pathway expression patterns of 7 patient clusters (Fig 1a) confirmed our prior characterization of 200 non-overlapping SLE patients.2The biomarker subset retained a trend of longer time to first flare in patients receiving obexelimab (n=38) vs placebo (n=33) (Fig1b, HR 0.61, p=0.11). A smaller set of only Clusters 3 and 6 demonstrated marked increased time to flare in the obexelimab group (n=13) compared to placebo (n=14) (Fig 1c, HR 0.22, p=0.025). Obexelimab had no effect on other clusters (Fig 1d). The responder clusters shared low expression of inflammation modules (p < 0.001) compared to other clusters and high expression of T Cell, immune response, cell cycle, mitochondrial modules (all p < 0.001) and B Cell modules (p=0.006). We therefore sorted patients by these specific features regardless of cluster assignment. Figure 2 shows significant impact of obexelimab on time to flare in 64 patients with B Cell pathway activation (HR 0.5, p=0.038), although less robust by itself than found in Clusters 3 and 6. In a group with high B or plasma cell modules but low inflammation (n=46), treatment effect increased (HR 0.35, p=0.019). Between Screening and Baseline, as brief steroids were given and background treatments withdrawn, expression of B Cell and Plasma Cell pathways increased. Both then decreased after treatment with obexelimab but not placebo (p< 0.0001 and p< 0.001 respectively), an effect not seen with other immune pathway modules.

Conclusion:

Precision medicine for SLE has been hampered by heterogenous immune signals with variable expression. Clustering of patients by gene co-expression pathways enabled an efficient, hierarchical array that reduplicated results of a prior SLE cohort, suggesting these are not random phenotypes. Of these 7 reproducible SLE subsets, the combination of clusters 3 and 6 distinguished an obexelimab responder population of 27 out of 71 subjects (38%) with high expression of B and T Cell modules and cell activation pathways. Focus on the defining features shared by these clusters revealed specific factors associated with response, enabling inclusion of some patients from other clusters in an optimized responder population of 46/71 (65% of subjects). B Cell and Plasma Cell pathways demonstrated mechanism-related pharmacodynamic effects of obexelimab. Lack of responders with high expression of inflammation modules could implicate inhibitory factors to obexelimab within inflammatory pathways, potentially targetable by complementary treatments.

References:

[1]Banchereau Cell 165:1548 2016

[2]Lu ACR Abstract #2977 2017

[3]Merrill Arthritis Rheumatol 69: 1257 2017

Disclosure of Interests: :

Joan T Merrill Grant/research support from: Xencor, Bristol Myers Squibb, Glaxo Smith Kline, Consultant of: Xencor, Abbvie, UCB, Glaxo Smith Kline, EMD Serono, Astellas, Remegen, Celgene/Bristol Myers Squibb, Exagen, Astra Zeneca, Amgen, Jannsen, Servier, ILTOO, Daitchi Sankyo, Lilly, Paid instructor for: Abbvie, Bristol Myers Squibb, Joel Guthridge Grant/research support from: Xencor, Bristol Myers Squibb, DXterity, Debra Zack Shareholder of: Xencor, Employee of: Xencor, Paul Foster Shareholder of: Xencor Inc, Employee of: Xencor Inc, Bart Burington Shareholder of: Xencor Inc, Employee of: Xencor Inc, Ly Tran: None declared, Miles Smith: None declared, Judith A. James Grant/research support from: Progentec Diagnostics, Inc, Consultant of: Abbvie, Novartis, Jannsen

OP0047 GENOME-WIDE ASSOCIATION STUDY OF SJÖGREN’S SYNDROME IDENTIFIES TEN NEW RISK LOCI

Background:

Sjögren’s syndrome (SS) is a complex autoimmune disease with exocrine gland dysfunction leading to substantial morbidity. There are 10 published genetic susceptibility loci.

Objectives:

Our genome-wide association study (GWAS) aimed to identify additional risk loci of genome-wide significance (GWS; p<5E-08) in European-derived primary SS.

Methods:

A total of 3232 cases and 17481 controls genotyped on GWAS arrays and 619 cases and 6171 controls genotyped on ImmunoChip (IC) arrays were imputed after quality control. Logistic regression was calculated adjusting for ancestry using the first 4 principal components to identify SS-associated SNPs. GWAS and IC results were meta-analyzed using weighted Z-scores. Bayesian statistics were used to assign posterior probabilities and define credible SNP sets for each locus. Bioinformatic analyses were used to predict functionality.

Results:

Seven novel loci exceeded GWS in the GWAS analysis:NAB1,MIR146A-PTTG1,XKR6,MAPT-CRHR1,RPTOR-CHMP6-BAIAP2,TYK2andSYNGR1. Meta-analysis with IC data identified three more novel loci exceeding GWS:CD247,PRDM1-ATG5andTNFAIP3. Several additional loci with suggestive association (p<1E-05) were also identified:ADAMTSL2,CGNL1andPHRF1.

Several identified loci have reported functional implications in immune regulation and autoimmune disease. In lupus, rs2431697 correlated with rs2431098, which was shown to alterMIR146Aexpression, resulting in type I interferon pathway imbalance. Similarly,TYK2risk association reportedly drives interferon, IL10 and RET signaling pathways.PRDM1encodes Blimp-1, a master regulator of immune cell differentiation.CD247encodes the zeta subunit of the T cell receptor complex.XKR6is implicated in apoptotic cell ingestion.ATG5is also involved in apoptosis, as well as autophagy and antigen presentation.

Additional bioinformatics analyses (Haploreg, Regulome DB, ENCODE, etc.) revealed immune-relevant functional implications for each risk locus. The SS-associated credible set included variants downstream ofTNFAIP3in a region reported to abolish looping between an enhancer and theTNFAIP3promoter in lupus and a coding variant that has been shown to alter NF-kB activity and neutrophil extra-cellular traps. The rs2293765 in the 5’ UTR ofNAB1showed evidence of enhancer/promoter activities. The rs2069235 in theSYNGR1locus showed enhancer and transcription start site activities in B and T cells. The rs7210219 in theMAPT-CRHR1locus showed enhancer/promotor activities in various tissues.

Conclusion:

We have identified ten novel genetic susceptibility loci associated with SS pathology. Our finding increases the current number of GWS regions in SS patients of European origin, from 10 to 20. Future work is needed to identify and characterize the functional variants in each region.

Disclosure of Interests:

Bhuwan Khatri: None declared, Tove Ragna Reksten: None declared, Kandice L Tessneer: None declared, Astrid Rasmussen Speakers bureau: Novartis, ThermoFischer, R Hal Scofield Grant/research support from: Pfizer, Simon J. Bowman Consultant of: Astrazeneca, Biogen, BMS, Celgene, Medimmune, MTPharma, Novartis, Ono, UCB, xtlbio, Glapagos, Speakers bureau: Novartis, Joel Guthridge Grant/research support from: Xencor, Bristol Myers Squibb, DXterity, Judith A. James Grant/research support from: Progentec Diagnostics, Inc, Consultant of: Abbvie, Novartis, Jannsen, Lars Ronnblom Grant/research support from: AZ, Speakers bureau: AZ, Blake M Warner: None declared, Xavier Mariette: None declared, Roald Omdal: None declared, Javier Martin Ibanez: None declared, Maria Teruel: None declared, Janicke Liaaen Jensen: None declared, Lara A Aqrawi: None declared, Øyvind Palm: None declared, Marie Wahren-Herlenius: None declared, Torsten Witte: None declared, Roland Jonsson: None declared, Maureen Rischmueller: None declared, A Darise Farris Speakers bureau: Biogen, Marta Alarcon-Riquelme: None declared, Wan-fai Ng: None declared, Kathy L Sivils: None declared, Gunnel Nordmark: None declared, Christopher Lessard: None declared

Author Correction: Tubular cell and keratinocyte single-cell transcriptomics applied to lupus nephritis reveal type I IFN and fibrosis relevant pathways

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Site-1 protease deficiency causes human skeletal dysplasia due to defective inter-organelle protein trafficking

Site-1 protease (S1P), encoded by MBTPS1, is a serine protease in the Golgi. S1P regulates lipogenesis, endoplasmic reticulum (ER) function, and lysosome biogenesis in mice and in cultured cells. However, how S1P differentially regulates these diverse functions in humans has been unclear. In addition, no human disease with S1P deficiency has been identified. Here, we report a pediatric patient with an amorphic and a severely hypomorphic mutation in MBTPS1. The unique combination of these mutations results in a frequency of functional MBTPS1 transcripts of approximately 1%, a finding that is associated with skeletal dysplasia and elevated blood lysosomal enzymes. We found that the residually expressed S1P is sufficient for lipid homeostasis but not for ER and lysosomal functions, especially in chondrocytes. The defective S1P function specifically impairs activation of the ER stress transducer BBF2H7, leading to ER retention of collagen in chondrocytes. S1P deficiency also causes abnormal secretion of lysosomal enzymes due to partial impairment of mannose-6-phosphate-dependent delivery to lysosomes. Collectively, these abnormalities lead to apoptosis of chondrocytes and lysosomal enzyme-mediated degradation of the bone matrix. Correction of an MBTPS1 variant or reduction of ER stress mitigated collagen-trafficking defects. These results define a new congenital human skeletal disorder and, more importantly, reveal that S1P is particularly required for skeletal development in humans. Our findings may also lead to new therapies for other genetic skeletal diseases, as ER dysfunction is common in these disorders.

A potential link between immune response to a periodontal bacterium, Aggregatibacter actinomycetemcomintans and Systemic Lupus Erythematosus

Infections are a significant cause of morbidity in Systemic Lupus Erythematosus (SLE). Although oral health is considerably compromised in SLE patients, the role of oral pathogens in influencing lupus pathogenesis is not known. In the present study, antibody responses to a periodontogenic, facultative anaerobic bacterium, Aggregatibacter actinomycetemcomitans (Aa), (which serve as an indicator of past or ongoing infection with Aa), were measured in SLE patients (n=587) and healthy controls (n=75). The associations between anti-Aa antibody titers and clinical measures of SLE were evaluated. The effect of Aa infection on development of lupus was investigated in the NZM2328 mice. The ability of Aa to induce neutrophil extracellular traps (NETs) was studied in vitro.

Both SLE patients and controls showed the presence of anti-Aa. In SLE patients, the anti-Aa titers correlated strongly with anti-dsDNA, anti-chromatin, anti-RNP, and anti-Sm; but not with anti-Ro52, anti-Ro60, and anti-La antibodies. NZM2328 mice developed a robust immune response to Aa, and the Aa infection caused an accelerated onset of autoantibody and renal disease. In addition, Aa readily induced NETosis in NZM2328 neutrophils.

Our data suggest for the first time that SLE patients are exposed to oral pathogen Aa, and this exposure significantly influences immune responses against a subset of lupus-associated autoantigens, possibly through NETosis. Furthermore, our studies suggest that management of oral health in SLE patients might prove to be beneficial for controlling lupus.

Altered soluble mediator levels and systemic lupus erythematosus-specific Connective Tissue Disease Screening Questionnaire (CSQ) scores differentiate unaffected relatives of lupus patients from healthy individuals with no family history of SLE (CCR4P.214)

Identifying populations at risk of SLE who remain unaffected would provide insights for potential disease prevention. Using a unique resource of SLE patient family members, first degree relatives (FDRs) of SLE patients (n = 154) with plasma samples available from previous genetic studies and who remained unaffected at follow-up evaluation (mean time = 6.8 years) were matched to healthy individuals unrelated to SLE patients (Controls). FDRs and Controls provided clinical and demographic information, and completed screening questionairres at baseline (BL) and follow-up (FU). BL and FU plasma samples were assessed for autoantibody production and soluble mediators. FDRs had significantly higher BL and FU CSQ scores (p&lt;0.0001), but no difference in the number of positive autoantibodies compared to Controls. FDRs had significant (p &lt; 0.01) increases in 38 (of 52) soluble mediators at BL and FU, including IFN-associated chemokines, TNFR ligands, and regulatory mediators (p&lt;0.002). Levels of MIP-1α (p=0.008), MIG (p=0.019), GROα (p=0.001), ICAM-1 (p=0.007), and VEGF (p=0.004), along with CSQ scores (p=0.010), best distinguished FDRs from Controls in logistic regression models. These alterations are present despite lack of progression to classified SLE, suggesting that multiple perturbations in immune-mediated inflammatory processes present in FDRs of SLE patients may be offset by inhibitory factors.

Autoantibody-positive healthy individuals display unique immune profiles that regulate autoimmunity (HUM3P.244)

Antinuclear antibodies (ANA) are detected in up to 25% of the population, yet only 5-8% develop autoimmunity. Immunological differences between ANA+ healthy individuals and SLE patients may give us insight into mechanisms by which ANA+ individuals avoid autoimmunity or transition to SLE. European-American ANA+ individuals (n=31) were matched to ANA- controls and SLE patients. Serum cytokine profiles, lymphocyte subset frequency, and lymphocyte reactivity were analyzed. Numerous pro-inflammatory cytokines including IFNγ, IL-2, IL-5 and TNFα were elevated in the serum of ANA+ healthy individuals compared to ANA- controls; however, SLE patients had even higher cytokine levels compared to ANA+ healthy individuals (p&gt;0.05). Interestingly, Type I IFNs, BLyS, IL-12p40 and SCF were only increased in SLE patients (p&lt;0.05). Further, IL-1RA was decreased in both ANA+ and SLE individuals (p&lt;0.0001). Total monocytes and memory B cells, were elevated in ANA+ individuals compared with ANA- controls while regulatory CD4+ T cells were decreased (p&lt;0.05). Further, monocytes and B cells from ANA+ individuals had increased levels of pSTAT1 and pSTAT3 following IFN-α stimulation compared to controls (p&lt;0.05). These data reveal ANA+ healthy individuals exhibit similar features to SLE patients with increased inflammation and loss of immune tolerance, but differ by the absence of elevated Type I IFNs, BLyS, IL-12p40 and SCF and severely decreased IL-1RA that contribute to disease pathogenesis.

Altered innate, adaptive, and TNF-superfamily soluble inflammatory mediators mark impending systemic lupus erythematosus disease flare, while regulatory mediators distinguish lack of impending disease flare in African-American lupus patients (CCR5P.201)

SLE is a multifaceted disease characterized by immune dysregulation and varied disease activity. We evaluated changes in plasma soluble mediators (n=52) preceding clinically-defined disease flare, in 13 African American (AA) SLE patients who developed disease flare 6 or 12 weeks after baseline assessment compared to matched SLE patients without impending flare and healthy controls. In addition, mediators within samples preceding SLE disease flare and during a clinically stable period from the same individual were compared in 18 AA SLE patients. Patients with impending flare had significant (q&lt;0.01) alterations in 32 soluble mediators at baseline with significantly higher levels of pro-inflammatory mediators, including innate and adaptive cytokines. Baseline levels of regulatory cytokines, including IL-10 and TGF-β, were higher in non-flare SLE patients, while baseline levels of soluble TNFRI, TNFRII, TRAIL, FasL, and CD40L were significantly greater in pre-flare patients (p&lt;0.05). A normalized and weighted combined soluble mediator score was significantly higher in pre-flare SLE patients versus those with stable disease (p&lt;0.0001). Pro-inflammatory soluble mediators are elevated prior to disease flare, while regulatory mediators are elevated during periods of stable disease. Alterations in the balance between inflammatory and regulatory mediators may help identify AA patients at risk of disease flare and help decipher SLE pathogenic mechanisms.

Comparison of systemic lupus erythematosus and healthy anti-nuclear antibody positive African-Americans reveals distinct differences in CD4+ and CD8+ T cell populations (BA3P.117)

Systemic lupus erythematosus (SLE) is an autoimmune disorder arising from genetic and environmental factors that likely affect phenotypic and functional characteristics of multiple cell lineages. Almost all SLE individuals are antinuclear antibody positive (ANA+) although ANA positivity does not obligate autoimmune disease. The differences in cell physiology between ANA+ healthy individuals and individuals that go on to develop SLE remains a critical goal in understanding SLE development. We visualized the expression of 33 cellular markers through the hierarchical clustering of SPADE to provide a comprehensive view of the immune system between ANA- African Americans (n=8), ANA+ healthy controls (n=8) and ANA+ patients with SLE (n=8). In addition, the levels of 51 cytokines were measured in plasma using a multiplex immunoassay. Compared to healthy controls, SLE patients had lower frequencies of cytotoxic CD8+ T cells and regulatory CD4+ T cells (P&lt;0.05). Concentrations of serum sCD40 ligand were reduced in patients with SLE compared with ANA+ and ANA- healthy controls (p&lt;0.05). Interestingly, sCD40L production positively correlated with a decrease in regulatory CD4+ T cell populations (p&lt;0.01). IL-7 levels were lower in both ANA+ controls and SLE patients compared with ANA- healthy individuals (p&lt;0.05). Our results indicate that early differences in IL-7 may contribute to decreased levels of regulatory CD8+ and CD4+ T cells important for controlling systemic inflammation.

Dysregulation of type II interferon associated mediators precedes autoantibody accumulation and type I interferon elevation and predicts transition to systemic lupus erythematosus classification (BA3P.109)

Autoantibodies and interferon (IFN) are associated with clinical illness in systemic lupus erythematosus (SLE), but how these factors influence autoimmune disease development is unknown. This study evaluates the timing and changes in SLE-linked autoantibody specificities, serum IFN-α activity, and IFN-associated soluble mediator levels in the years preceding SLE classification. Serial sera from 55 SLE cases spanning pre- and post-SLE classification (average time = 4.3 years) and matched healthy controls (HC) were obtained from the Department of Defense Serum Repository. Cases with positive serum IFN-α activity had more SLE-linked autoantibody specificities (p&lt;0.05). Growth curve modeling and path analysis corroborated that most autoantibody specificities precede IFN-α activity, and IFN-γ and IP-10 were elevated prior to or concurrent with autoantibody positivity (p&lt;0.01). The number of autoantibody specificities and IFN-associated soluble mediators, as well as female gender, predicted increases in IFN-α activity (p&lt;0.04; ANCOVA). IFN-γ and MCP-3 levels, as well as the presence of anti-chromatin and spliceosomal autoantibodies, best predicted transition to SLE with 93% accuracy &gt;4 years before SLE classification (Random Forest). These data indicate that pre-clinical immune system perturbations allow for the accumulation of autoantibodies and subsequent elevation in IFN-α activity immediately preceding clinical symptoms and SLE classification.

Soluble mediators and clinical features predict transition to systemic lupus erythematosus classification in previously unaffected relatives of SLE patients (HUM3P.243)

Healthy relatives of lupus patients have an increased risk of developing SLE, but predictors and mechanisms of disease transition are unknown. Unaffected relatives of SLE patients (n=409) were enrolled in this follow-up study to identify factors associated with transition to SLE. Participants provided detailed demographic and clinical information, including the Connective Tissue Disease Screening Questionnaire (CSQ). Medical records were reviewed for ACR classification criteria. Plasma samples were tested for the presence of autoantibodies and soluble mediators. Forty-five relatives (11%) transitioned to classified SLE during follow-up (mean time = 6.4 years) who had more autoantibodies (p&lt;0.0001) and higher pre-classification (baseline) CSQ scores (p&lt;0.0001). Relatives who transitioned also had elevated baseline levels of inflammatory mediators, including BLyS, SCF, and IFN-associated chemokines (p&lt;0.05), with concurrent decreased regulatory mediators, including TGF-β and IL-10 (p&lt;0.05). Logistic regression analysis revealed that baseline ACR and CSQ scores (but not autoantibodies), and baseline plasma levels of SCF and TGF-β were significant and independent predictors of SLE transition. Thus, perturbations in immune-mediated processes precede SLE clinical classification and can help identify unaffected relatives at highest risk of future SLE classification for early intervention studies.

Altered adaptive and TNF-superfamily soluble inflammatory mediators mark impending Systemic Lupus Erythematosus disease flare in European-American lupus patients after influenza vaccination (P6282)

SLE is a waxing and waning disease characterized by major organ involvement, disease flares and immune dysregulation. Understanding mechanisms and identifying biomarkers of flare would help prevent damage and improve management. Plasma samples were obtained from SLE patients on the day of influenza vaccination (BL) and at 6 and 12 weeks post (FU) in 28 European American SLE patients who exhibited SELENA-SLEDAI defined disease flare at 6 (n=13) or 12 (n=15) weeks post-vaccination. Each SLE patient was matched to a unique SLE patient who did not flare (NF), and to a healthy control (HC). Samples from 13 SLE patients with flare were compared to samples from a non-flare year (self nonflare, SNF). Plasma samples were tested for 52 soluble inflammatory mediators using xMAP technology. SLE patients who exhibited disease flare had significantly (p &lt; 0.01) higher levels of BL pro-inflammatory mediators, including Th1, Th2, and Th17-type cytokines compared to NF/SNF SLE patients and HC. Regulatory cytokines, including IL-10 and TGF-β were increased (p &lt; 0.01) at BL in SLE patients not exhibiting disease flare (NF/SNF) compared to SLE flare and HC. TNFR family members, TNFRI, TNFRII, Fas, FasL, CD40L, were increased at BL in SLE flare patients. Select serum cytokines and chemokines are elevated in patients before SLE disease flare, providing important pathways to dissect for mechanism of flare, therapeutic selection or development.

Functional characterization of the MECP2/IRAK1 lupus risk haplotype in human T cells and a human MECP2 transgenic mouse (P3319)

Genetic polymorphism in MECP2/IRAK1 is a confirmed susceptibility locus for lupus. DNA methylation changes in T cells play a central role in the pathogenesis of lupus, and MeCp-2 is a master regulator of gene expression and is known to recruit DNA methyltransferase 1 (DNMT1) during DNA synthesis. Using human T cells from normal individuals, we demonstrate that the lupus risk variant in MECP2/IRAK1 increases MECP2 mRNA expression in stimulated T cells. By assessing DNA methylation levels at ~ 485,000 methylation sites across the genome, we further show that the lupus risk variant in this locus is associated with significant DNA methylation changes, including in the HLA-DR and HLA-DQ loci, as well as interferon-related genes such as IFI6, IRF6, and BST2. Further, using a human MECP2 transgenic mouse, we show that overexpression of MECP2 alters gene expression in stimulated T cells. This includes overexpression of Eif2c2 that regulates the expression of multiple microRNAs (such as miR-21), and the histone demethylase Jhdm1d. We also show that MECP2 transgenic mice develop antinuclear antibodies. Our data suggest that the lupus associated variant in the MECP2/IRAK1 locus has the potential to affect all 3 epigenetic mechanisms. Importantly, we demonstrate that variants within the MECP2 gene can alter DNA methylation in other genetic loci including the HLA and interferon-regulated genes, thereby providing evidence for genetic-epigenetic interaction in lupus.

IRF5 Genetic Risk Haplotype Influences Host B Cell Gene Responses to Epstein-Barr Virus (EBV) (49.14)

Both gene and environment interactions play keyroles in the development of systemic lupus erythematosus (SLE). We examined effects of the IRF5 lupus risk haplotype upon the host's B cell response to the binding or infection with EBV, a suspected environmental trigger for SLE. Whole genome microarray expression profile data was collected from cells exposed to EBV for 16 hours. Analysis of gene expression by gene set enrichment analysis revealed that key differences in expression between SLE patients and controls (or individuals carrying the IRF5 risk and non-risk haplotype) were in a subset of interferon response genes. Patients with the IRF5 risk haplotype have a heightened interferon signature under all experimental conditions; whereas, the patients with the IRF5 protective haplotype have a B cell interferon signature similar to that of unrelated, matched controls. Overexpression of interferon pathway genes in B cells following viral exposure in control individuals carrying the IRF5 risk haplotype suggests that the IRF5 risk alleles alone can modulate ones biological response to the environmental insult. Patients carrying either the IRF5 risk or non-risk alleles appear to already be predisposed to having a higher interferon signature even without exposure to virus, suggesting that other genetic factors are also influencing the interferon response, independent of virus. Support by NIH (AI007633 and AI31584).

C8orf13/BLK association with systemic lupus erythematosus across different ethnicities (136.28)

SLE is a complex autoimmune disease with immunological abnormalities that targets B cell functions and development. Previous genome-wide association studies identified C8orf13/BLK as a novel SLE risk factor. BLK (B lymphoid tyrosine kinase) has been shown to have potential effects on B cell develoment. The main objectives of this study are to: 1.) assess this association in independent populations and 2.) determine if BLK risk alleles correlate with alteration in peripheral blood B cell development and protein expression. We genotyped 52 SNPs within the C8orf13/BLK region in European-derived, Asian and African American populations. rs13277113 is associated with SLE in all three populations. A few novel upstream SNPs within the intergenic region demonstrate a stronger association in Asians. Flow cytometry data suggests there is a significant difference in BLK expression and T2 cells B cell numbers between high-risk and non-risk individuals based on the risk haplotype. Our results suggest that the BLK genetic polymorphisms alter immune system development and function to increase the risk for SLE development. Supported by NIH RR020143, RR015577, NIAID-DAIT-BAA-05-11, AI031584, AR053483, AR48940, AI063274, AR052125, AR043247 and OCAST # HR08-037.

Systemic lupus erythematosus (SLE) and chromosome 16: confirmation of linkage to 16q12-13 and evidence for genetic heterogeneity

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease with significant morbidity and mortality, characterized by remarkable clinical variability with unknown etiology. Genetic contribution to the development of SLE is well established. Recently, we found evidence (P<0.004) of linkage at 16p13 and 16q12-13 in a genome scan based on 37 Hispanic families. The main objective of this study is to replicate and confirm the linkage at these two genomic locations in two large independent replication data sets designated as, group-1 and group-2, consisting of 172 and 120 multiplex SLE families, respectively. We have found a significant evidence of linkage with high heterogeneity (HLOD=4.85, alpha=35%) at 16q12-13 in group-2. Other independent research groups also reported the SLE susceptibility at or close to 16q12-13 previously. Therefore, independent published reports, together with our initial linkage with Hispanics and followed by significant evidence from group-2, provide a strong and confirmed evidence for an SLE susceptibility locus at 16q12-13.

Characterization of a complement receptor 2 (CR2, CD21) ligand binding site for C3. An initial model of ligand interaction with two linked short consensus repeat modules

Human CR2 (CD21, EBV receptor) is an approximately 145-kDa receptor and a member of the regulators of complement activation gene family. Regulators of complement activation proteins are characterized by the presence of repeating motifs of 60 to 70 amino acids that are designated short consensus repeats (SCR). CR2 serves as a receptor for four distinct ligands. Three of these ligands (complement C3, gp350/220 of EBV, and CD23) interact with the amino terminal 2 of 16 SCR (SCR 1 and 2). Previous studies have determined that at least four sites are important in allowing CR2 to efficiently bind EBV. Two of these sites are also important for binding mAb OKB7, a reagent that blocks both EBV and iC3b/C3dg binding to CR2. We have identified and characterized important sites of iC3b ligand binding by utilizing human-mouse CR2 chimeras, a rat anti-mouse CR2 mAb designated 4E3 that blocks receptor binding to C3, and human CR2-derived peptides. In addition to demonstrating an important role for the same sequence in SCR 1 that is part of the mAb OKB7 and EBV binding site, we have identified a new region within SCR 2 that interacts with C3. These results, when compared with a model of a dual SCR solution structure derived from human factor H SCR, predict that two distinct largely surface-exposed sites on CR2 interact with iC3b. A relative twist of 130 degrees about the long axis of the second SCR in this model would be necessary for these sites to form a single patch for iC3b binding on CR2.

Characterization of a complement receptor 2 (CR2, CD21) ligand binding site for C3. An initial model of ligand interaction with two linked short consensus repeat modules

Human CR2 (CD21, EBV receptor) is an approximately 145-kDa receptor and a member of the regulators of complement activation gene family. Regulators of complement activation proteins are characterized by the presence of repeating motifs of 60 to 70 amino acids that are designated short consensus repeats (SCR). CR2 serves as a receptor for four distinct ligands. Three of these ligands (complement C3, gp350/220 of EBV, and CD23) interact with the amino terminal 2 of 16 SCR (SCR 1 and 2). Previous studies have determined that at least four sites are important in allowing CR2 to efficiently bind EBV. Two of these sites are also important for binding mAb OKB7, a reagent that blocks both EBV and iC3b/C3dg binding to CR2. We have identified and characterized important sites of iC3b ligand binding by utilizing human-mouse CR2 chimeras, a rat anti-mouse CR2 mAb designated 4E3 that blocks receptor binding to C3, and human CR2-derived peptides. In addition to demonstrating an important role for the same sequence in SCR 1 that is part of the mAb OKB7 and EBV binding site, we have identified a new region within SCR 2 that interacts with C3. These results, when compared with a model of a dual SCR solution structure derived from human factor H SCR, predict that two distinct largely surface-exposed sites on CR2 interact with iC3b. A relative twist of 130 degrees about the long axis of the second SCR in this model would be necessary for these sites to form a single patch for iC3b binding on CR2.