Age- and sex-related patterns of serum interferon-alpha activity in lupus families

HERC6 regulates STING activity in a sex-biased manner through modulation of LATS2/VGLL3 Hippo signaling

Interferon (IFN) activity exhibits a gender bias in human skin, skewed toward females. We show that HERC6, an IFN-induced E3 ubiquitin ligase, is induced in human keratinocytes through the epidermal type I IFN; IFN-κ. HERC6 knockdown in human keratinocytes results in enhanced induction of interferon-stimulated genes (ISGs) upon treatment with a double-stranded (ds) DNA STING activator cGAMP but not in response to the RNA-sensing TLR3 agonist. Keratinocytes lacking HERC6 exhibit sustained STING-TBK1 signaling following cGAMP stimulation through modulation of LATS2 and TBK1 activity, unmasking more robust ISG responses in female keratinocytes. This enhanced female-biased immune response with loss of HERC6 depends on VGLL3, a regulator of type I IFN signature. These data identify HERC6 as a previously unrecognized negative regulator of ISG expression specific to dsDNA sensing and establish it as a regulator of female-biased immune responses through modulation of STING signaling.

A Comprehensive Literature Review on Managing Systemic Lupus Erythematosus: Addressing Cardiovascular Disease Risk in Females and Its Autoimmune Disease Associations

This review aimed to evaluate the mechanism of premature cardiovascular disease (CVD) in systemic lupus erythematosus (SLE) patients, particularly in the female population, and emphasize the need for early management interventions; explore the association between SLE and two autoimmune diseases, myasthenia gravis (MG) and antiphospholipid antibody syndrome (APS), and their management strategies; and evaluate the effectiveness of pharmacological and non-pharmacological interventions in managing SLE, focusing on premenopausal females, females of childbearing age, and pregnant patients. We conducted a comprehensive literature review to achieve these objectives using various databases, including PubMed, Google Scholar, and Cochrane. The collected data were analyzed and synthesized to provide an evidence-based overview of SLE, its management strategies as an independent disease, and some disease associations. The treatment should be focused on remission, preventing organ damage, and improving the overall quality of life (QOL). Extensive emphasis should also be focused on diagnosing SLE and concurrent underlying secondary diseases timely and managing them appropriately.

Type I interferon pathway assays in studies of rheumatic and musculoskeletal diseases: a systematic literature review informing EULAR points to consider

OBJECTIVES

To systematically review the literature for assay methods that aim to evaluate type I interferon (IFN-I) pathway activation and to harmonise-related terminology.

METHODS

Three databases were searched for reports of IFN-I and rheumatic musculoskeletal diseases. Information about the performance metrics of assays measuring IFN-I and measures of truth were extracted and summarised. A EULAR task force panel assessed feasibility and developed consensus terminology.

RESULTS

Of 10 037 abstracts, 276 fulfilled eligibility criteria for data extraction. Some reported more than one technique to measure IFN-I pathway activation. Hence, 276 papers generated data on 412 methods. IFN-I pathway activation was measured using: qPCR (n=121), immunoassays (n=101), microarray (n=69), reporter cell assay (n=38), DNA methylation (n=14), flow cytometry (n=14), cytopathic effect assay (n=11), RNA sequencing (n=9), plaque reduction assay (n=8), Nanostring (n=5), bisulphite sequencing (n=3). Principles of each assay are summarised for content validity. Concurrent validity (correlation with other IFN assays) was presented for n=150/412 assays. Reliability data were variable and provided for 13 assays. Gene expression and immunoassays were considered most feasible. Consensus terminology to define different aspects of IFN-I research and practice was produced.

CONCLUSIONS

Diverse methods have been reported as IFN-I assays and these differ in what elements or aspects of IFN-I pathway activation they measure and how. No 'gold standard' represents the entirety of the IFN pathway, some may not be specific for IFN-I. Data on reliability or comparing assays were limited, and feasibility is a challenge for many assays. Consensus terminology should improve consistency of reporting.

Relationship of systemic type I interferon activity with clinical phenotypes, disease activity, and damage accrual in systemic lupus erythematosus in treatment-naive patients: a retrospective longitudinal analysis

BACKGROUND

Systemic lupus erythematosus (SLE) is heterogeneous in organ involvement and disease severity, presenting a broad clinical phenotype. Systemic type I interferon (IFN) activity has been shown to be associated with lupus nephritis, autoantibodies, and disease activity in treated SLE patients; however, these relationships are unknown in treatment-naive patients. We aimed to determine the relationship of systemic IFN activity with clinical phenotypes, disease activity, and damage accrual in treatment-naive SLE patients before and after induction and maintenance therapy.

METHODS

Forty treatment-naive SLE patients were enrolled for this retrospective longitudinal observational study to examine the relationship between serum IFN activity and clinical manifestations of EULAR/ACR-2019 criteria domains, disease activity measures, and damage accrual. As controls, 59 other treatment-naive rheumatic disease patients and 33 healthy individuals were recruited. Serum IFN activity was measured by WISH bioassay and presented as an IFN activity score.

RESULTS

Treatment-naive SLE patients had significantly higher serum IFN activity than other rheumatic disease patients (score: 97.6 and 0.0, respectively, p < 0.001). High serum IFN activity was significantly associated with fever, hematologic disorders (leukopenia), and mucocutaneous manifestations (acute cutaneous lupus and oral ulcer) of EULAR/ACR-2019 criteria domains in treatment-naive SLE patients. Serum IFN activity at baseline significantly correlated with SLEDAI-2K scores and decreased along with a decrease in SLEDAI-2K scores after induction and maintenance therapy (R² = 0.112, p = 0.034). SLE patients who developed organ damage (SDI ≥ 1) had higher serum IFN activity at baseline than those who did not (SDI = 0) (150.0 versus 57.3, p= 0.018), but the multivariate analysis did not detect its independent significance (p = 0.132).

CONCLUSIONS

Serum IFN activity is characteristically high and is linked to fever, hematologic disorders, and mucocutaneous manifestations in treatment-naive SLE patients. Serum IFN activity at baseline correlates with disease activity and decreases in parallel with a decrease in disease activity after induction and maintenance therapy. Our results suggest that IFN plays an important role in the pathophysiology of SLE and that serum IFN activity at baseline may be a potential biomarker for the disease activity in treatment-naive SLE patients.

Ablation of SigH+ pDCs in B6.Nba2 mice prevents lupus-like disease development only if started before disease is fully established

Systemic lupus erythematosus is characterized by hyper-activation of the immune system, multi-organ inflammation, and end-organ damage. Type I interferons (IFN-I) have been strongly implicated a role in disease etiology as has the main IFN-I-producing cell subset, the plasmacytoid dendritic cell (pDC). The B6.Nba2 mouse model develops a lupus-like disease characterized by elevated IFN-I levels and pDC pathogenicity. We have previously shown that pDC ablation prior to disease development in B6.Nba2 mice effectively prevents disease; however, it remains unclear if a similar protection can be seen if pDC ablation is initiated during later disease stages. This is important as Systemic lupus erythematosus patients are rarely diagnosed until disease is well-established and thus preventative treatment is unlikely to take place. Here we show that ablation of pDCs in the B6.Nba2 mouse model must be initiated early in order to effectively block disease development and that sustained reduction in pDC numbers is necessary for sustained effects. Finally, targeting of pDCs have been hypothesized to affect immunity towards infectious agents, in particular virus and intracellular bacteria. We show here that pDC ablation in B6.Nba2 mice does not affect the anti-viral response to encephalomyocarditic virus or a model T-dependent antigen. In summary, pDC ablation does not affect general immunity, but needs to happen early and be sustained to prevent lupus-like disease development in B6.Nba2 mice.

APOL1 variant-expressing endothelial cells exhibit autophagic dysfunction and mitochondrial stress

Polymorphisms in the Apolipoprotein L1 (APOL1) gene are common in ancestrally African populations, and associate with kidney injury and cardiovascular disease. These risk variants (RV) provide an advantage in resisting Trypanosoma brucei, the causal agent of African trypanosomiasis, and are largely absent from non-African genomes. Clinical associations between the APOL1 high risk genotype (HRG) and disease are stronger in those with comorbid infectious or immune disease. To understand the interaction between cytokine exposure and APOL1 cytotoxicity, we established human umbilical vein endothelial cell (HUVEC) cultures representing each APOL1 genotype. Untreated HUVECs were compared to IFNɣ-exposed; and APOL1 expression, mitochondrial function, lysosome integrity, and autophagic flux were measured. IFNɣ increased median APOL1 expression across all genotypes 22.1 (8.3 to 29.8) fold (p=0.02). Compared to zero risk variant-carrying HUVECs (0RV), HUVECs carrying 2 risk variant copies (2RV) showed both depressed baseline and maximum mitochondrial oxygen consumption (p<0.01), and impaired mitochondrial networking on MitoTracker assays. These cells also demonstrated a contracted lysosomal compartment, and an accumulation of autophagosomes suggesting a defect in autophagic flux. Upon blocking autophagy with non-selective lysosome inhibitor, hydroxychloroquine, autophagosome accumulation between 0RV HUVECs and untreated 2RV HUVECs was similar, implicating lysosomal dysfunction in the HRG-associated autophagy defect. Compared to 0RV and 2RV HUVECs, HUVECs carrying 1 risk variant copy (1RV) demonstrated intermediate mitochondrial respiration and autophagic flux phenotypes, which were exacerbated with IFNɣ exposure. Taken together, our data reveal that IFNɣ induces APOL1 expression, and that each additional RV associates with mitochondrial dysfunction and autophagy inhibition. IFNɣ amplifies this phenotype even in 1RV HUVECs, representing the first description of APOL1 pathobiology in variant heterozygous cell cultures.

Single-cell RNA-seq reveals cell type-specific molecular and genetic associations to lupus

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease. Knowledge of circulating immune cell types and states associated with SLE remains incomplete. We profiled more than 1.2 million peripheral blood mononuclear cells (162 cases, 99 controls) with multiplexed single-cell RNA sequencing (mux-seq). Cases exhibited elevated expression of type 1 interferon-stimulated genes (ISGs) in monocytes, reduction of naïve CD4+ T cells that correlated with monocyte ISG expression, and expansion of repertoire-restricted cytotoxic GZMH+ CD8+ T cells. Cell type-specific expression features predicted case-control status and stratified patients into two molecular subtypes. We integrated dense genotyping data to map cell type-specific cis-expression quantitative trait loci and to link SLE-associated variants to cell type-specific expression. These results demonstrate mux-seq as a systematic approach to characterize cellular composition, identify transcriptional signatures, and annotate genetic variants associated with SLE.

High Systemic Type I Interferon Activity is Associated with Active Class III/IV Lupus Nephritis

OBJECTIVE

Previous studies suggest a link between high serum type I interferon (IFN) and lupus nephritis (LN). We determined whether serum IFN activity is associated with subtypes of LN and studied renal tissues and cells to understand the impact of IFN in LN.

METHODS

221 systemic lupus erythematosus (SLE) patients were studied. Serum IFN activity was measured by WISH bioassay. mRNA in-situ hybridization was used in renal tissue to measure expression of the representative IFN-induced gene, interferon-induced protein with tetratricopeptide repeats-1 (IFIT1), and the plasmacytoid dendritic cell (pDC) marker gene C-type lectin domain family-4 member C (CLEC4C or BDCA2). Podocyte cell line gene expression was measured by real-time PCR.

RESULTS

Class III/IV LN prevalence was significantly increased in patients with high serum IFN compared with those with low IFN (OR=5.48, p=4.0x10-7). In multivariate regression models, type I IFN was a stronger predictor of class III/IV LN than complement C3 or anti-dsDNA antibody, and could account for the association of these variables with LN. IFIT1 expression was increased in all classes of LN, but most in the glomerular areas of active class III/IV LN kidneys. IFIT1 expression was not closely co-localized with pDCs. IFN directly activated podocyte cell lines to induce chemokines and proapoptotic molecules.

CONCLUSION

Systemic high IFN is involved in the pathogenesis of severe LN. We do not find co-localization of pDCs with IFN signature in renal tissue, and instead observe the greatest intensity of IFN signature in glomerular areas, which could suggest a blood source of IFN.

Inhibition of mTOR suppresses IFNα production and the STING pathway in monocytes from systemic lupus erythematosus patients

OBJECTIVE

Increased IFNα is important in the pathogenesis of SLE. Plasmacytoid dendritic cells are considered the main producer of IFNα upon Toll-like receptor pathway activation. However, which cells produce IFNα following stimulation with cyclic GMP-AMP synthase (cGAS) and stimulator of IFN genes (STING) in SLE remains unknown. We investigated the IFNα producing capacity of myeloid cells under cGAS-STING pathway stimulation.

METHODS

IFNα levels in peripheral blood mononuclear cells from SLE patients and healthy controls stimulated with 2'3'c-GAMP, a stimulator of cGAS-STING, were measured by intracellular cytokine staining and flow cytometry. STING expression and its co-localization with TBK1 were examined by flow cytometry or confocal microscopy. The effects of in vitro exposure to IFNα on IFNα production and STING expression, and in vitro rapamycin treatment on IFNα production and STING, pTBK1 and IRF3 expression were examined.

RESULTS

IFNα was produced by monocytes, conventional dendritic cells and plasmacytoid dendritic cells upon cGAS-STING pathway activation. The frequency of IFNα-producing monocytes positively correlated with SLE disease activity. STING expression and its co-localization with TBK1 were increased in lupus monocytes. Prior exposure to IFNα enhanced the IFNα-producing capacity of monocytes. Inhibition of the mechanistic target of the rapamycin (mTOR) pathway suppressed IFNα production from monocytes and downregulated enhanced STING expression and its downstream molecules.

CONCLUSION

Enhanced IFNα from lupus monocytes induced by augmented STING pathway activation is associated with SLE pathogenesis. Suppression of the mTOR pathway downregulated the enhanced STING expression and the subsequent IFNα production by monocytes.

The baseline interferon signature predicts disease severity over the subsequent 5 years in systemic lupus erythematosus

Objectives

Type I interferons (IFNs) play an important role in the pathophysiology of systemic lupus erythematosus (SLE). While cross-sectional data suggest an association between IFN-induced gene expression and SLE disease activity, interest in this as a biomarker of flare has been tempered by a lack of fluctuation with disease activity in the majority of patients. This led us to question whether IFN-induced gene expression might instead be a biomarker of overall disease severity, with patients with high levels spending more time in an active disease state.

Methods

Levels of five interferon-responsive genes were measured in the whole peripheral blood at baseline visit for 137 SLE patients subsequently followed for 5 years. Log transformed values were summed to yield a composite IFN5 score, and the correlation with various disease outcomes examined. Receiver operator characteristic analyses were performed for outcomes of interest. Kaplan-Meier curves were generated to compare the proportion of flare-free patients with high and low IFN5 scores over time.

Results

The baseline IFN5 score was positively correlated with the adjusted mean SLE disease activity index-2000, number of flares, adjusted mean prednisone dose, and number of new immunosuppressive medications over the subsequent 5 years. Optimal cut-offs for the IFN5 score were determined using Youden’s index and predicted more severe outcomes with 57–67% accuracy. A high baseline IFN5 level was associated with a significantly increased risk of subsequent flare.

Conclusions

Measurement of the type I IFN signature is a useful tool for predicting the subsequent disease activity course.

SIGLEC1 (CD169) is a sensitive biomarker for the deterioration of the clinical course in childhood systemic lupus erythematosus

Background

To analyse the validity of membrane-bound SIGLEC1 (CD169) as a sensitive biomarker for monitoring disease activity in pediatric systemic lupus erythematosus (SLE).

Methods

27 children and adolescents with SLE were followed for a mean of 13.5 months. During consecutive routine visits SLEDAI-2k, C3, C4 and ds-DNA values were determined. Additionally, expression of SIGLEC1 on monocytes was determined by flow cytometry. The amount of PE-labelled CD169 mAb bound per monocyte was analyzed using QuantiBRITE™ PE tubes. Associations between biomarkers and the clinical course were investigated by regression analysis.

Results

In general, SIGLEC1 expression is high on SLE-derived monocytes (mean 6 359 (SD 6 056) molecules/monocyte, cut-off 2 500 molecules/monocyte), all patients with newly diagnosed SLE exhibit elevated expression (mean 13366 (SD 7 750) molecules/monocyte). Changes (Δ) in SIGLEC1 levels during the clinical course is the only biomarker that significantly correlates with the change in SLEDAI-2k (beta_ST = 0.28, p = 0.001). At follow-up visit, a clinically important worsening was experienced by 47.6% of patients with a Δ SIGLEC1 > 2 151 molecules/cell (OR 5.31) and 72.4% with a Δ SIGLEC1 > 756 molecules/cell (OR 8.90). Conversely, 36.4% of patients with a Δ SIGLEC1 < -2 818 molecules/cell (OR 4.16, percentiles as cut-off criteria) and 50.0% of patients with a Δ SIGLEC1 < -1 370 molecules/cell (OR 3.55, application of Youden index) showed clinical improvement. SIGLEC1 expression correlates inversely with the amount of therapeutically applied hydroxychloroquine (p < 0.001).

Conclusions

SIGLEC1 expression on monocytes is a sensitive biomarker for adjusting disease activity in childhood SLE and represents a promising and easily applicable tool for disease monitoring.

Sex differences in neutrophil biology modulate response to type I interferons and immunometabolism

Differences between female and male immunity may contribute to variations in response to infections and predisposition to autoimmunity. We previously reported that neutrophils from reproductive-age males are more immature and less activated than their female counterparts. To further characterize the mechanisms that drive differential neutrophil phenotypes, we performed RNA sequencing on circulating neutrophils from healthy adult females and males. Female neutrophils displayed significant up-regulation of type I IFN (IFN)-stimulated genes (ISGs). Single-cell RNA-sequencing analysis indicated that these differences are neutrophil specific, driven by a distinct neutrophil subset and related to maturation status. Neutrophil hyperresponsiveness to type I IFNs promoted enhanced responses to Toll-like receptor agonists. Neutrophils from young adult males had significantly increased mitochondrial metabolism compared to those from females and this was modulated by estradiol. Assessment of ISGs and neutrophil maturation genes in Klinefelter syndrome (47, XXY) males and in prepubescent children supported that differences in neutrophil phenotype between adult male and female neutrophils are hormonally driven and not explained by X chromosome gene dosage. Our results indicate that there are distinct sex differences in neutrophil biology related to responses to type I IFNs, immunometabolism, and maturation status that may have prominent functional and pathogenic implications.

Type I Interferon Predicts an Alternate Immune System Phenotype in Systemic Lupus Erythematosus

Objective

Type I interferon (IFN) is important to systemic lupus erythematosus (SLE) pathogenesis, but it is not clear how chronic elevations in IFN alter immune function. We compared cytokine responses after whole blood stimulation with Toll‐like receptor (TLR) agonists in high‐ and low‐IFN SLE patient subgroups.

Methods

SLE patients and nonautoimmune controls were recruited, and SLE patients were categorized as either high or low IFN. Whole blood was dispensed into tubes coated with lipopolysaccharide (LPS), oligonucleotides with cytosine‐guanine repeats, Resiquimod, IFN‐α, and IFN‐α + LPS. Cytokine production in patient sera and after whole blood TLR stimulation was measured by multiplex assay, and type I IFN was assessed using a functional assay.

Results

Circulating plasmacytoid dendritic cell numbers were specifically reduced in high‐IFN SLE patients and not in low‐IFN SLE patients. In serum, we observed that the correlations between cytokines in serum differed to a much greater degree between the high‐ and low‐IFN groups (P < 0.0001) than the absolute cytokine levels differed between these same groups. In stimulated conditions, the high‐IFN patients had less cytokine production in response to TLR ligation than the low‐IFN SLE patients. LPS produced the most diverse response, and a number of interactions between type I IFN and LPS were observed.

Conclusion

We find striking differences in resting and stimulated cytokine patterns in high‐ vs. low‐IFN SLE patients, which supports the biological importance of these patient subsets. These data could inform personalized treatment approaches and the pathogenesis of SLE flare following infection.

Interferon pathway in SLE: one key to unlocking the mystery of the disease

SLE is characterised by an activation of the interferon (IFN) system, which leads to an increased expression of IFN-regulated genes. The reasons behind the IFN signature in SLE are (1) the existence of endogenous IFN inducers, (2) activation of several IFN-producing cell types, (3) production of many different IFNs, (4) a genetic setup promoting IFN production and (5) deficient negative feedback mechanisms. The consequences for the immune system is a continuous stimulation to an immune response, and for the patient a number of different organ manifestations leading to typical symptoms for SLE. In the current review, we will present the existing knowledge of the IFN system and pathway activation in SLE. We will also discuss how this information can contribute to our understanding of both the aetiopathogenesis and some organ manifestations of the disease. We will put forward some issues that are unresolved and should be clarified in order to make a proper stratification of patients with SLE, which seems important when selecting a therapy aiming to downregulate the IFN system.

Novel genetic associations with interferon in systemic lupus erythematosus identified by replication and fine-mapping of trait-stratified genome-wide screen

BACKGROUND/PURPOSE

High serum interferon alpha (IFN-α) is an important heritable phenotype in systemic lupus erythematosus (SLE) which is involved in primary disease pathogenesis. High vs. low levels of IFN-α are associated with disease severity and account for some of the biological heterogeneity between SLE patients. The aim of the study was to replicate and fine-map previously detected genetic associations with serum IFN-α in SLE.

METHODS

We previously undertook a case-case genome-wide association study of SLE patients stratified by ancestry and extremes of phenotype in serum IFN-α. Single nucleotide polymorphisms (SNPs) in seven loci identified in this screen were selected for follow up in a large independent cohort of 1370 SLE patients (703 European-ancestry, 432 African ancestry, and 235 Amerindian ancestry). Each ancestral background was analyzed separately, and ancestry-informative markers were used to control for ancestry and admixture.

RESULTS

We find a rare haplotype spanning the promoter region of EFNA5 that is strongly associated with serum IFN-α in both African-American and European-American SLE patients (OR = 3.0, p = 3.7 × 10^-6). We also find SNPs in the PPM1H, PTPRM, and NRGN regions associated with IFN-α levels in European-American, Amerindian, and African-American SLE patients respectively. Many of these associations are within regulatory regions of the gene, suggesting an impact on transcription.

CONCLUSION

This study demonstrates the power of molecular sub-phenotypes to reveal genetic factors involved in complex autoimmune disease. The distinct associations observed in different ancestral backgrounds emphasize the heterogeneity of molecular pathogenesis in SLE.

Conventional DCs from Male and Female Lupus-Prone B6.NZM Sle1/Sle2/Sle3 Mice Express an IFN Signature and Have a Higher Immunometabolism That Are Enhanced by Estrogen

Type I interferons (IFN) are pathogenic in systemic lupus erythematosus (SLE) and were proposed to control the immunometabolism of dendritic cells (DCs). We previously reported that DCs from female lupus-prone mice constitutively overexpress IFN-responsive genes resembling the IFN signature found in SLE patients. As SLE has higher incidence in women than men, more so in women of reproductive age, estrogens are suggested to affect lupus pathogenesis. We investigated the effects of sex and estrogens on the IFN signature in conventional GM-CSF-bone marrow-derived DCs (cDCs), from male and female Triple Congenic B6.NZM.Sle1/Sle2/Sle3 (TCSle) lupus-prone mice or from wild-type C57BL/6 mice, generated with titrations of 17-beta-estradiol (E2). We found that cDCs from prediseased TCSle male mice express the IFN signature as female TCSle cDCs do. Estrogens are necessary but not sufficient to express this IFN signature, but high doses of E2 can compensate for other steroidal components. E2 stimulation, regardless of sex, modulates type I IFN-dependent and type I IFN-independent activation of cDCs in response to TLR stimulation. Finally, we found that TCSle cDCs from both sexes have elevated markers of immunometabolism and estrogens enhance the metabolic pathways in cDCs, suggesting a mechanistic link between estrogens, immunometabolism, and the IFN signature in lupus.

Associations between type I interferon and antiphospholipid antibody status differ between ancestral backgrounds

OBJECTIVE

The type I interferon pathway is activated in many patients with systemic lupus erythematosus (SLE), and anti-double-stranded DNA (dsDNA) and anti-RNA binding protein autoantibodies are correlated with high interferon-α (IFNα) activity. We studied whether antiphospholipid (APL) antibodies, which should not stimulate Toll-like receptors, are also associated with high levels of IFNα activity.

METHODS

Serum IFNα activity was measured in patients with SLE using the WISH cell bioassay. IgG APL, anti-RBP and anti-dsDNA antibodies were measured in the clinical laboratory, and standard clinical cut-offs were used to define the positive results.

RESULTS

High IFNα activity was associated with anti-RBP and anti-dsDNA antibodies in all three ancestral backgrounds. Strikingly, African-American subjects with a positive APL antibody test had higher IFNα activity than those without IgG APL antibodies. This was not shared with other ancestral backgrounds. This finding was independent of other autoantibody profiles, and clinical features did not differ between IgG APL antibody positive versus negative African-American patients.

CONCLUSION

The difference in association between IFNα activity and IgG APL status between ancestral backgrounds supports differences in molecular pathogenesis. This may suggest B cell hyperactivity in the setting of type I IFN in African-Americans and could suggest ways to individualise therapy.

Lupus-Associated Functional Polymorphism in PNP Causes Cell Cycle Abnormalities and Interferon Pathway Activation in Human Immune Cells

OBJECTIVE

Systemic lupus erythematosus (SLE) is frequently characterized by activation of the type I interferon (IFN) pathway. We previously observed that a missense single-nucleotide polymorphism (rs1049564) in the purine nucleoside phosphorylase (PNP) gene was associated with high levels of IFN in SLE. PNP is a key enzyme involved in purine metabolism. In this study, we performed functional follow-up of this polymorphism in human cells.

METHODS

Type I IFN was measured in patient sera, using a reporter cell assay. Structural modeling of the PNP variant was performed using PyMOL software. PNP messenger RNA (mRNA) and protein levels and type I IFN-induced gene expression were measured in lymphoblastoid cell lines with known PNP rs1049564 genotypes. The cell cycle was assayed using flow cytometry.

RESULTS

Structural modeling indicated no major disruption in folding related to rs1049564. We observed that homozygous rs1049564 TT lymphoblastoid cells had decreased PNP mRNA expression and protein levels, and that cells with the TT genotype had reduced PNP enzymatic activity even when the amount of PNP was controlled. Cells with the TT genotype had a 2-fold increase in S-phase block as compared with cells with the homozygous CC phenotype. The S-phase block could be pharmacologically reversed with hypoxanthine and adenosine, supporting the notion that relative PNP deficiency is the cause of the S-phase block. Type I IFN-induced transcripts were increased in a dose-response manner related to the rs1049564 T allele, at both baseline and after type I IFN stimulation.

CONCLUSION

The PNP rs1049564 T allele is a loss-of-function variant that induces S-phase block and IFN pathway activation in lymphocytes. The S-phase block could be rescued in our in vitro experiments, suggesting the potential for personalized treatment.

Enhanced IFN-α production is associated with increased TLR7 retention in the lysosomes of palasmacytoid dendritic cells in systemic lupus erythematosus

Background

Interferon-α (IFN-α) is increased and plays an important role in the pathogenesis of systemic lupus erythematosus (SLE). Plasmacytoid dendritic cells (pDCs) are the main producer of IFN-α, but their IFN-α producing capacity has been shown to be unchanged or reduced when stimulated with a Toll-like receptor 9 (TLR9) agonist in patients with SLE compared to in healthy individuals. In this study, we investigated the IFN-α-producing capacity of lupus pDCs under different stimulation.

Methods

pDCs from patients with SLE and healthy controls (HC) were stimulated with TLR9 or TLR7 agonist, and their IFN-α producing capacity was examined by intracellular cytokine staining and flow cytometry. The correlation of IFN-α-producing capacity with serum IFN-α levels and disease activity was assessed. The effect of in vitro IFN-α exposure on IFN-α production by pDCs was examined. Localization of TLR7 in cellular compartments in pDCs was investigated.

Results

The IFN-α producing capacity of pDCs was reduced after TLR9 stimulation, but increased when stimulated with a TLR7 agonist in SLE compared to in HC. IFN-α production by pDCs upon TLR9 stimulation was reduced and the percentage of IFN-α⁺pDC was inversely correlated with disease activity and serum IFN-α levels. However, the TLR7 agonist-induced IFN-α producing capacity of lupus pDCs was enhanced and correlated with disease activity and serum IFN-α. Exposure to IFN-α enhanced IFN-α production of TLR7-stimulated pDCs, but reduced that of pDCs activated with a TLR9 agonist. TLR7 localization was increased in late endosome/lysosome compartments in pDCs from SLE patients.

Conclusions

These findings indicate that enhanced TLR7 responses of lupus pDCs, owing to TLR7 retention in late endosome/lysosome and exposure to IFN-α, are associated with the pathogenesis of SLE.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1441-7) contains supplementary material, which is available to authorized users.

Type I interferon-mediated autoimmune diseases: pathogenesis, diagnosis and targeted therapy

Type I interferons (IFN-Is) are a group of molecules with pleiotropic effects on the immune system forming a crucial link between innate and adaptive immune responses. Apart from their important role in antiviral immunity, IFN-Is are increasingly recognized as key players in autoimmune CTDs such as SLE. Novel therapies that target IFN-I appear effective in SLE in early trials, but effectiveness is related to the presence of IFN-I biomarkers. IFN-I biomarkers may also act as positive or negative predictors of response to other biologics. Despite the high failure rate of clinical trials in SLE, subgroups of patients often respond better. Fully optimizing the potential of these agents is therefore likely to require stratification of patients using IFN-I and other biomarkers. This suggests the unified concept of type I IFN-mediated autoimmune diseases as a grouping including patients with a variety of different traditional diagnoses.

Serum IL-18 as biomarker in predicting long-term renal outcome among pediatric-onset systemic lupus erythematosus patients

An urge of biomarker identification is needed to better monitor lupus nephritis (LN) disease activity, guide clinical treatment, and predict patient's long-term outcome. With the proinflammatory effect and its association with inflammasomes, the significance of interleukin-18 (IL-18) among pediatric-onset systemic lupus erythematous (pSLE) patient, especially, its importance in predicting long-term renal outcome was investigated.In a pSLE cohort of 96 patients with an average follow-up period of 10.39 ± 3.31 years, clinical data and laboratory workups including serum IL-18 were collected at time of disease onset and 6 months after treatment despite their initial renal status. Through Cox regression analysis, the parameters at baseline and at 6 months posttreatment were carefully analyzed.Average age of all cases was 12.74 ± 3.01 years old and 65 of them underwent renal biopsy at the time of diagnosis. Nine subjects (9.38%) progressed to end-stage renal disease (ESRD) and 2 cases (2.08%) died during follow-up. Through multivariate analysis, serum IL-18 level 6 months posttreatment was found to be the most unfavorable factor associating poor clinical outcome despite patient's initial renal status. In addition, the presentation of serum IL-18 in its correlation with SLE global disease activity as well as the presence and severity of LN were all significant (P < 0.001, P = 0.03, and P = 0.02, respectively). The histological classification of LN, however, was not associated with the level of IL-18 among the pSLE patients (P = 0.64).The role of serum IL-18 as biomarker representing global disease activity and status of renal flares among pSLE population was shown for the first time. Additionally, we have identified IL-18 at 6 months posttreatment a novel marker for long-term renal outcome prediction.

Advances in lupus genetics

PURPOSE OF REVIEW

The field of systemic lupus erythematosus (SLE) genetics has been advancing rapidly in recent years. This review will summarize recent advances in SLE genetics.

RECENT FINDINGS

Genome-wide-association and follow-up studies have greatly expanded the list of associated polymorphisms, and much current work strives to integrate these polymorphisms into immune system biology and the pathogenic mediators involved in the disease. This review covers some current areas of interest, including genetic studies in non-European SLE patient populations, studies of pathogenic immune system subphenotypes such as type I interferon and autoantibodies, and a rapidly growing body of work investigating the functional consequences of the genetic polymorphisms associated with SLE.

SUMMARY

These studies provide a fascinating window into human SLE disease biology. As the work proceeds from genetic association signal to altered human biology, we move closer to tailoring interventions based upon an individual's genetic substrate.

The genetics of human autoimmune disease: A perspective on progress in the field and future directions

Progress in defining the genetics of autoimmune disease has been dramatically enhanced by large scale genetic studies. Genome-wide approaches, examining hundreds or for some diseases thousands of cases and controls, have been implemented using high throughput genotyping and appropriate algorithms to provide a wealth of data over the last decade. These studies have identified hundreds of non-HLA loci as well as further defining HLA variations that predispose to different autoimmune diseases. These studies to identify genetic risk loci are also complemented by progress in gene expression studies including definition of expression quantitative trait loci (eQTL), various alterations in chromatin structure including histone marks, DNase I sensitivity, repressed chromatin regions as well as transcript factor binding sites. Integration of this information can partially explain why particular variations can alter proclivity to autoimmune phenotypes. Despite our incomplete knowledge base with only partial definition of hereditary factors and possible functional connections, this progress has and will continue to facilitate a better understanding of critical pathways and critical changes in immunoregulation. Advances in defining and understanding functional variants potentially can lead to both novel therapeutics and personalized medicine in which therapeutic approaches are chosen based on particular molecular phenotypes and genomic alterations.

Age-Related Differences in Percentages of Regulatory and Effector T Lymphocytes and Their Subsets in Healthy Individuals and Characteristic STAT1/STAT5 Signalling Response in Helper T Lymphocytes

The dynamic process of the development of the immune system can in itself result in age-related immune malfunctions. In this study, we analysed lymphocyte subsets in the peripheral blood of 60 healthy donors, divided into groups of children, adolescents, and adults, focusing on effector (Teff) and regulatory (Treg) T lymphocytes and STAT1/STAT5 signalling response in helper T lymphocytes (Th) in adults, using flow cytometry. Our results demonstrate a decrease in the percentage of total Tregs and an increase in the percentage of total Teffs with age and a consequential immense increase in the Teff/Treg ratio. The increase of Teffs was most apparent in Th1, Th1Th17, and Th17CD161- subsets. Significant Th lymphocyte STAT1 expression differences were observed between children and adolescents, which were associated with the decrease in activated Tregs. Higher expression of STAT1 was found in FoxP3hi than in FoxP3low Th lymphocytes, while significant IL-2 induced STAT5 phosphorylation differences were found among the subsets of Th lymphocytes in adults. Our study demonstrates age-related changes in circulating Teff and Treg, as well as significant differences in STAT5/STAT1 signalling among FoxP3+ Th lymphocytes, providing new advances in the understanding of immunosenescence.

The type I interferons: Basic concepts and clinical relevance in immune-mediated inflammatory diseases

There is increasing scientific and clinical interest in elucidating the biology of type I Interferons, which began approximately 60 years ago with the concept of "viral interference", a property that reduces the ability of a virus to infect cells. Although our understanding of the multiple cellular and molecular functions of interferons has advanced significantly, much remains to be learned and type I Interferons remain an active and fascinating area of inquiry. In this review, we cover some general aspects of type I interferon genes, with emphasis on interferon-alpha, and various aspects of molecular mechanisms triggered by type I interferons and toll-like receptor signaling by the Janus activated kinase/signal transducer activation of transcription (JAK-STAT) pathway and interferon regulatory factor pathway. We will also describe the role of type I interferons in autoimmune and inflammatory diseases, and its potential use as therapeutic agent.

Serum interleukin-17 levels are associated with nephritis in childhood-onset systemic lupus erythematosus

OBJECTIVES

To determine the serum interleukin-17 (IL-17) levels in childhood-onset systemic lupus erythematosus patients and to evaluate the association between IL-17 and clinical manifestations, disease activity, laboratory findings and treatment.

METHODS

We included 67 consecutive childhood-onset systemic lupus erythematosus patients [61 women; median age 18 years (range 11-31)], 55 first-degree relatives [50 women; median age 40 years (range 29-52)] and 47 age- and sex-matched healthy controls [42 women; median age 19 years (range 6-30)]. The childhood-onset systemic lupus erythematosus patients were assessed for clinical and laboratory systemic lupus erythematosus manifestations, disease activity [Systemic Lupus Erythematosus Disease Activity Index (SLEDAI)], cumulative damage [Systemic Lupus International Collaborating Clinics/American College of Rheumatology (ACR) Damage Index] and current drug use. Serum IL-17 levels were measured by an enzyme-linked immunosorbent assay using commercial kits.

RESULTS

The median serum IL-17 level was 36.3 (range 17.36-105.92) pg/mL in childhood-onset systemic lupus erythematosus patients and 29.47 (15.16-62.17) pg/mL in healthy controls (p=0.009). We observed an association between serum IL-17 levels and active nephritis (p=0.01) and migraines (p=0.03). Serum IL-17 levels were not associated with disease activity (p=0.32), cumulative damage (p=0.34), or medication use (p=0.63).

CONCLUSION

IL-17 is increased in childhood-onset systemic lupus erythematosus and may play a role in the pathogenesis of neuropsychiatric and renal manifestations. Longitudinal studies are necessary to determine the role of IL-17 in childhood-onset systemic lupus erythematosus.

Interferon regulatory factors: critical mediators of human lupus

The pathogenesis of systemic lupus erythematosus (SLE) is multifactorial, and the interferon regulatory factors (IRFs) play an important role. Autoantibodies formed in SLE target nuclear antigens, and immune complexes formed by these antibodies contain nucleic acid. These immune complexes can activate antiviral pattern recognition receptors (PRRs), resulting in the downstream activation of IRFs, which can induce type I interferon (IFN-I) and other inflammatory mediators. Genetic variations in IRFs have been associated with susceptibility to SLE, and current evidence supports the idea that these polymorphisms are gain of function in humans. Recent studies suggest that these genetic variations contribute to the break in humoral tolerance that allows for nucleic acid binding autoantibodies, and that the same polymorphisms also augment IFN-I production in the presence of these autoantibody immune complexes, forming a feed-forward loop. In this review, we will outline major features of the PRR/IRF systems and describe the role of the IRFs in human SLE pathogenesis.

Dysregulation of antiviral helicase pathways in systemic lupus erythematosus

In the autoimmune disease systemic lupus erythematosus (SLE), our normal antiviral defenses are inappropriately activated, resulting in over-activity of the type I interferon (IFN) pathway. This increased activity of the type I IFN pathway is an important primary pathogenic factor in the disease. Emerging evidence has implicated the antiviral helicases in this process. The antiviral helicases normally function as nucleic acid receptors in viral immunity. Genetic variations in antiviral helicase genes have been associated with SLE, supporting the idea that helicase pathways are involved in the primary pathogenesis of SLE. Studies have documented functional consequences of these genetic variations within the type I IFN pathway in human cell lines and SLE patients. In this review, we summarize the function of helicases in the anti-viral immune response, and how this response is dysregulated in SLE patients. In particular, we will focus on known functional genetic polymorphisms in the IFIH1 (MDA5) and mitochondrial antiviral signaling protein genes which have been implicated in human SLE. These data provide fascinating evidence for dysregulation of helicase-mediated innate immunity in SLE, and may support novel therapeutic strategies in the disease.

Systemic Lupus Erythematosus: Old and New Susceptibility Genes versus Clinical Manifestations

Systemic Lupus Erythematosus (SLE) is one of the most relevant world-wide autoimmune disorders. The formation of autoantibodies and the deposition of antibody-containing immune complexes in blood vessels throughout the body is the main pathogenic mechanism of SLE leading to heterogeneous clinical manifestations and target tissue damage. The complexity of etiology and pathogenesis in SLE, enclosing genetic and environmental factors, apparently is one of the greatest challenges for both researchers and clinicians. Strong indications for a genetic background in SLE come from studies in families as well as in monozygotic and dizygotic twins, discovering several SLE-associated loci and genes (e.g. IRF5, PTPN22, CTLA4, STAT4 and BANK1). As SLE has a complex genetic background, none of these genes is likely to be entirely responsible for triggering autoimmune response in SLE even if they disclosure a potentially novel molecular mechanisms in the pathogenesis' disease. The clinical manifestations and disease severity varies greatly among patients, thus several studies try to associate clinical heterogeneity and prognosis with specific genetic polymorphisms in SLE associated genes. The continue effort to describe new predisposing or modulating genes in SLE is justified by the limited knowledge about the pathogenesis, assorted clinical manifestation and the possible prevention strategies. In this review we describe newly discovered, as well as the most studied genes associated to SLE susceptibility, and relate them to clinical manifestations of the disease.

Genetics of the type I interferon pathway in systemic lupus erythematosus

Genetic studies of systemic lupus erythematosus (SLE) have been successful, identifying numerous risk factors for human disease. While the list is not yet complete, it is clear that important immune system pathways are represented, one of which being type I interferon (IFN). Circulating type I IFN levels are high in SLE patients and this IFN pathway activation is heritable in families with SLE. We summarize our current understanding of the genetics of the type I IFN pathway in SLE, with an emphasis on studies that demonstrate an impact of the SLE-risk alleles upon type I IFN pathway activation in SLE patients. These studies illustrate that variations in type I IFN pathway genes represent a common genetic feature of SLE. By understanding the genetic regulation of type I IFN, we may be able to intervene in a more personalized fashion, based upon the molecular dysregulation present in a given individual.

Activation of the Interferon Pathway is Dependent Upon Autoantibodies in African-American SLE Patients, but Not in European-American SLE Patients

Background: In systemic lupus erythematosus (SLE), antibodies directed at RNA-binding proteins (anti-RBP) are associated with high serum type I interferon (IFN), which plays an important role in SLE pathogenesis. African-Americans (AA) are more likely to develop SLE, and SLE is also more severe in this population. We hypothesized that peripheral blood gene expression patterns would differ between AA and European-American (EA) SLE patients, and between those with anti-RBP antibodies and those who lack these antibodies.

Methods: Whole blood RNA from 33 female SLE patients and 16 matched female controls from AA and EA ancestral backgrounds was analyzed on Affymetrix Gene 1.0 ST gene expression arrays. Ingenuity Pathway Analysis was used to compare the top differentially expressed canonical pathways amongst the sample groups. An independent cohort of 116 SLE patients was used to replicate findings using quantitative real-time PCR (qPCR).

Results: Both AA and EA patients with positive anti-RBP antibodies showed over-expression of similar IFN-related canonical pathways, such as IFN Signaling (P = 1.3 × 10⁻⁷ and 6.3 × 10⁻¹¹ in AA vs. EA respectively), Antigen Presenting Pathway (P = 1.8 × 10⁻⁵ and 2.5 × 10⁻⁶), and a number of pattern recognition receptor pathways. In anti-RBP negative (RBP−) patients, EA subjects demonstrated similar IFN-related pathway activation, whereas no IFN-related pathways were detected in RBP−AA patients. qPCR validation confirmed similar results.

Conclusion: Our data show that IFN-induced gene expression is completely dependent on the presence of autoantibodies in AA SLE patients but not in EA patients. This molecular heterogeneity suggests differences in IFN-pathway activation between ancestral backgrounds in SLE. This heterogeneity may be clinically important, as therapeutics targeting this pathway are being developed.

The role of cytokines in the pathogenesis of systemic lupus erythematosus - from bench to bedside

The pathogenesis of systemic lupus erythematosus (SLE) entails a complex interaction between the different arms of the immune system. While autoantibodies production and immune complex deposition are cornered as hallmark features of SLE, there is growing evidence to propose the pathogenic role of cytokines in this disease. Examples of these cytokines include BLys, interleukin-6, interleukin-17, interleukin-18, type I interferons and tumour necrosis factor alpha. These cytokines all assume pivotal functions to orchestrate the differentiation, maturation and activation of various cell types, which would mediate local inflammatory process and tissue injury. The knowledge on these cytokines not only fosters our understanding of the disease, but also provides insights in devising biomarkers and targeted therapies. In this review, we focus on cytokines which have substantial pathogenic significance and also highlight the possible clinical applications of these cytokines.

Genetic variation near IRF8 is associated with serologic and cytokine profiles in systemic lupus erythematosus and multiple sclerosis

Alleles of IRF8 are associated with susceptibility to both systemic lupus erythematosus (SLE) and multiple sclerosis (MS). While high type I interferon (IFN) is thought to be causal in SLE, type I IFN is used as a therapy in MS. We investigated whether IRF8 alleles were associated with type I IFN levels or serologic profiles in SLE and MS. Alleles which have been previously associated with SLE or MS were genotyped in SLE and MS patients. The MS-associated rs17445836G allele was associated with anti-dsDNA autoantibodies in SLE patients (meta-analysis OR=1.92). The same allele was associated with decreased serum IFN activity in SLE patients with anti-dsDNA antibodies, and with decreased type I IFN-induced gene expression in PBMC from anti-dsDNA negative SLE patients. In secondary progressive MS patients, rs17445836G was associated with decreased serum type I IFN. Rs17445836G was associated with increased IRF8 expression in SLE patient B cells. In summary, IRF8 rs17445836G is associated with human autoimmune disease characterized by low type I IFN levels, and this may have pharmacogenetic relevance as type I IFN is modulated in SLE and MS. The association with autoantibodies and increased IRF8 expression in B cells supports a role for rs17445836G in humoral tolerance.

Update on differences between childhood-onset and adult-onset systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease and occurs worldwide in both children and adults. The estimated annual incidence among children is 2.22/100,000 and among adults is 23.2/100,000 in the United States. There is increasing understanding about differences in disease manifestations, medication use, and disease severity between those with childhood-onset SLE as compared with adult-onset SLE. Children have a more fulminant disease onset and course than adults with SLE, resulting in two to three times higher mortality. In future years, we anticipate more insight into the genetics between childhood-onset SLE and adult-onset SLE to help delineate the best therapies for both subsets of patients.

Th1/Th2 cytokine profile in childhood-onset systemic lupus erythematosus

OBJECTIVE

To determine the serum levels of Th1 (IL-12, IFN-γ,TNF-α) and Th2 (IL-5, IL-6 and IL-10) cytokines in childhood-onset SLE, first-degree relatives and healthy controls. To elucidate their association with disease activity, laboratory and treatment features.

METHODS

We included 60 consecutive childhood-onset SLE patients [median age 18 years (range 10-37)], 64 first-degree relatives [median 40 (range 28-52)] and 57 healthy [median age 19 years (range 6-30 years)] controls. Controls were age and sex-matched to SLE patients. SLE patients were assessed for clinical and laboratory SLE manifestations, disease activity (SLEDAI), damage (SDI) and current drug exposures. Mood and anxiety disorders were determined through Becks Depression (BDI) and Anxiety Inventory (BAI). Th1 (IL-12, IFN-γ,TNF-α) and Th2 (IL-5, IL-6 and IL-10) cytokines levels were measured by ELISA and compared by non-parametric tests.

RESULTS

Serum TNF-α (p=0.004), IL-6 (p=0.007) and IL-10 (p=0.03) levels were increased in childhood-onset SLE patients when compared to first-degree relatives and healthy controls. TNF-α levels were significantly increased in patients with active disease (p=0.014) and correlated directly with SLEDAI scores (r=0.39; p=0.002). IL-12 (p=0.042) and TNF-α (p=0.009) levels were significantly increased in patients with nephritis and TNF-α in patients with depression (p=0.001). No association between cytokine levels and SDI scores or medication was observed.

CONCLUSION

Th1 cytokines may play a role in the pathogenesis of neuropsychiatric and renal manifestations in childhood-onset SLE. The correlation with SLEDAI suggests that TNF-α may be a useful biomarker for disease activity in childhood-onset SLE, however longitudinal studies are necessary to determine if increase of this cytokine may predict flares in childhood-onset SLE.

Circulating interferon-α2 levels are increased in the majority of patients with systemic lupus erythematosus and are associated with disease activity and multiple cytokine activation

Mutations in interferon (IFN) regulatory factor genes and the biological activity of type I IFN on expression of specific genes that are induced by IFN have been associated with various aspects of systemic lupus erythematosus (SLE). Circulating levels of IFN-α in SLE has not been extensively studied because of limited sensitivity of available ELISA assays. We performed a cross-sectional case-control study where circulating levels of IFN-α2 were measured by a highly sensitive, solution phase multiplex magnetized bead assay and investigated the relation of IFN-α2 with autoantibody profiles, clinical disease activity and levels of inflammatory cytokines in SLE patients ( n = 87). Cytokine levels were determined on stored sera aliquots with cut-off levels determined by the geometric mean + 2SD in healthy controls ( n = 27). IFN-α2 levels were increased in 64% of SLE patients, who displayed more renal disease and higher disease activity ( p = 0.06) and had a significantly higher sum of activated cytokines (median 4.5, range 7) compared to patients with normal IFN-α2 (median one, range 3; p < 0.001). Solution phase micro-bead assay thus identified increased IFN-α2 levels in two-thirds of SLE patients with longstanding disease. The association with clinical disease and activation of multiple inflammatory cytokines supports a role for IFN-α2 in disease perpetuation in a large subset of SLE patients.

Interferon regulatory factor 5 in the pathogenesis of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by multiple genetic risk factors, high levels of interferon alpha (IFN-α), and the production of autoantibodies against components of the cell nucleus. Interferon regulatory factor 5 (IRF5) is a transcription factor which induces the transcription of IFN-α and other cytokines, and genetic variants of IRF5 have been strongly linked to SLE pathogenesis. IRF5 functions downstream of Toll-like receptors and other microbial pattern-recognition receptors, and immune complexes made up of SLE-associated autoantibodies seem to function as a chronic endogenous stimulus to this pathway. In this paper, we discuss the physiologic role of IRF5 in immune defense and the ways in which IRF5 variants may contribute to the pathogenesis of human SLE. Recent data regarding the role of IRF5 in both serologic autoimmunity and the overproduction of IFN-α in human SLE are summarized. These data support a model in which SLE-risk variants of IRF5 participate in a “feed-forward” mechanism, predisposing to SLE-associated autoantibody formation, and subsequently facilitating IFN-α production downstream of Toll-like receptors stimulated by immune complexes composed of these autoantibodies.

IFNα and its response proteins, IP-10 and SIGLEC-1, are biomarkers of disease activity in systemic lupus erythematosus

OBJECTIVES

To evaluate and compare the clinical efficacy of three biomarkers for interferon (IFN) activity (measured directly and indirectly) and six traditional biomarkers in indicating current and prospective disease activity (DA) in systemic lupus erythematosus (SLE).

METHODS

IFNα (dissociation-enhanced lanthanide fluorescent immunoassay), IFNγ-inducible protein 10 (IP-10) (ELISA) and sialic acid-binding Ig-like lectin 1 (SIGLEC-1) (flow cytometry) were measured in 79 accurately characterised patients with lupus and compared with serum titres of Anti-dsDNA (ELISA and radioimmunoassay), Anti-dsDNA-NcX ELISA, Anti-Nuc ELISA, and complement C3 and C4. DA was evaluated using the British Isles Lupus Assessment Group 2004 Index (BILAG-2004) and a modified SLE Disease Activity Index-2000 (mSLEDAI-2K). In addition, 31 clinically quiescent patients were monitored for flares over the course of 180 days.

RESULTS

Increased levels of IFNα, IP-10 and SIGLEC-1 were found in 32%, 50% and 86%, respectively, of 66 patients with active SLE. IFNα (r=0.45; p<0.0001) and SIGLEC-1 (r=0.54; p<0.0001) correlated better with BILAG-2004 than did IP-10 (r=0.38; p=0.0002), Farr assay (r=0.40; p=0.0001), Anti-dsDNA-NcX ELISA (r=0.28; p=0.0061), Anti-dsDNA ELISA (r=0.31; p=0.0025), Anti-Nuc ELISA (r=0.25; p=0.0121), C3 (r=-0.43; p<0.0001) and C4 (r=-0.33; p=0.0013). Predictors of SLE flares were disease duration ≤92 months, mild clinical activity (in contrast with no activity), complement C3≤89 mg/dl and IFNα≥20 pg/ml, while only lymphocyte count and age were independent predictors in multivariate analysis.

CONCLUSIONS

IFNα, IP-10 and SIGLEC-1 emerged as beneficial biomarkers of DA in patients with SLE. Therefore the implementation of IFN biomarkers in standard lupus diagnostics should be reappraised, especially in view of emerging anti-IFN-directed therapies.

Autoimmune heart disease: role of sex hormones and autoantibodies in disease pathogenesis

Cardiovascular disease (CVD) and autoimmune diseases (ADs) are the first and third highest causes of death in the USA, respectively. Men have an increased incidence of the majority of CVDs, including atherosclerosis, myocarditis, dilated cardiomyopathy and heart failure. By contrast, nearly 80% of all ADs occur in women. However, in one category of ADs, rheumatic diseases, CVD is the main cause of death. Factors that link rheumatic ADs to CVD are inflammation and the presence of autoantibodies. In this review we will examine recent findings regarding sex differences in the immunopathogenesis of CVD and ADs, explore possible reasons for the increased occurrence of CVD within rheumatic ADs and discuss whether autoantibodies, including rheumatoid factor, could be involved in disease pathogenesis.

Genetic ancestry, serum interferon-α activity, and autoantibodies in systemic lupus erythematosus

OBJECTIVE

To investigate and refine the relationships among systemic lupus erythematosus (SLE) and related autoantibodies, interferon-α (IFN-α), and various ancestral backgrounds.

METHODS

We investigated quantitatively defined genetic ancestry through principal component analysis in place of self-reported ancestry.

RESULTS

African ancestry was found to be associated with presence of anti-RNP antibody (p = 0.0026), and anti-RNP was correlated with high levels of IFN-α (p = 2.8 × 10(-5)).

CONCLUSION

Our data support a model in which African ancestry increases the likelihood of SLE-associated autoantibody formation, which subsequently results in higher levels of serum IFN-α.

Clinical and serological manifestations associated with interferon-α levels in childhood-onset systemic lupus erythematosus

OBJECTIVE

To determine the serum levels of interferon alpha in childhood-onset systemic lupus erythematosus patients, their first-degree relatives and healthy controls and to evaluate the associations between serum interferon alpha and disease activity, laboratory findings and treatment features.

METHODS

We screened consecutive childhood-onset systemic lupus erythematosus patients in a longitudinal cohort at the pediatric rheumatology unit of the State University of Campinas between 2009 and 2010. All patients demonstrated disease onset before the age of 16. Disease status was assessed according to the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) and Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI). Interferon alpha levels were measured using an enzyme-linked immunoabsorbent assay.

RESULTS

We included 57 childhood-onset systemic lupus erythematosus patients (mean age 17.33 ± 4.50), 64 first-degree relatives (mean age 39.95 ± 5.66), and 57 healthy (mean age 19.30 ± 4.97) controls. Serum interferon alpha levels were significantly increased in childhood-onset systemic lupus erythematosus patients compared to their first-degree relatives and healthy controls. Interferon alpha levels were significantly increased in patients with positive dsDNA antibodies, patients with cutaneous vasculitis, patients with new malar rash and patients who were not receiving medication. Interferon alpha levels correlated with C3 levels and systemic lupus erythematosus Disease Activity Index scores. In addition, we observed an inverse correlation between patient age and interferon alpha levels.

CONCLUSION

Interferon alpha may play a role in the pathogenesis of childhood-onset systemic lupus erythematosus, especially in cutaneous manifestations and dsDNA antibody formation. The observation that interferon alpha levels are increased in patients who are not taking medication should be investigated in longitudinal studies to determine whether elevated interferon alpha levels may predict systemic lupus erythematosus flares.

The autoimmune disease risk allele of UBE2L3 in African American patients with systemic lupus erythematosus: a recessive effect upon subphenotypes

OBJECTIVE

UBE2L3 is associated with susceptibility to systemic lupus erythematosus (SLE) and rheumatoid arthritis in European ancestry populations, and this locus has not been investigated fully in non-European populations. We studied the UBE2L3 risk allele for association with SLE, interferon-α (IFN-α), and autoantibodies in a predominantly African American SLE cohort.

METHODS

We studied 395 patients with SLE and 344 controls. The UBE2L3 rs5754217 polymorphism was genotyped using Taqman primer-probe sets, and IFN-α was measured using a reporter cell assay.

RESULTS

The UBE2L3 rs5754217 T allele was strongly enriched in African American patients with anti-La antibodies as compared to controls, and a recessive model was the best fit for this association (OR 2.55, p = 0.0061). Serum IFN-α also demonstrated a recessive association with the rs5754217 genotype in African American patients, and the TT/anti-La-positive patients formed a significantly high IFN-α subgroup (p = 0.0040). Similar nonstatistically significant patterns of association were observed in the European American patients with SLE. Case-control analysis did not show large allele frequency differences, supporting the idea that this allele is most strongly associated with anti-La-positive patients.

CONCLUSION

This pattern of recessive influence within a subgroup of patients may explain why this allele does not produce a strong signal in standard case-control studies, and subphenotypes should be included in future studies of UBE2L3. The interaction we observed between UBE2L3 genotype and autoantibodies upon serum IFN-α suggests a biological role for this locus in patients with SLE in vivo.

Influenza vaccination responses in human systemic lupus erythematosus: impact of clinical and demographic features

OBJECTIVE

Vaccination against common pathogens, such as influenza, is recommended for patients with systemic lupus erythematosus (SLE) to decrease infections and improve health. However, most reports describing the vaccination response are limited to evaluations of SLE patients with quiescent disease. This study focuses on understanding the clinical, serologic, therapeutic, and demographic factors that influence the response to influenza vaccination in SLE patients with a broad range of disease activity.

METHODS

Blood specimens and information on disease activity were collected from 72 patients with SLE, at baseline and at 2, 6, and 12 weeks after influenza vaccination. Influenza-specific antibody responses were assessed by determining the total serum antibody concentration (B(max)), relative affinity (K(a)), and level of hemagglutination inhibition in the plasma. Using a cumulative score, the patients were evenly divided into groups of high or low vaccine responders. Autoantibody levels were evaluated at each time point using immunofluorescence tests and standard enzyme-linked immunosorbent assays.

RESULTS

Compared to high responders, low responders to the vaccine were more likely to have hematologic criteria (P = 0.009), to have more American College of Rheumatology classification criteria for SLE (P = 0.05), and to be receiving concurrent prednisone treatment (P = 0.04). Interestingly, European American patients were more likely to be low responders than were African American patients (P = 0.03). Following vaccination, low responders were more likely to experience disease flares (P = 0.01) and to have increased titers of antinuclear antibodies (P = 0.04). Serum interferon-α activity at baseline was significantly higher in patients in whom a flare occurred after vaccination compared to a matched group of patients who did not experience a disease flare (P = 0.04).

CONCLUSION

Ancestral background, prednisone treatment, hematologic criteria, and evidence of increased likelihood of disease flares were associated with low antibody responses to influenza vaccination in SLE patients.

The dysregulation of cytokine networks in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease associated with chronic immune activation and tissue damage. Organ damage in SLE results from the deposition of immune complexes and the infiltration of activated T cells into susceptible organs. Cytokines are intimately involved in every step of the SLE pathogenesis. Defective immune regulation and uncontrolled lymphocyte activation, as well as increased antigen presenting cell maturation are all influenced by cytokines. Moreover, expansion of local immune responses as well as tissue infiltration by pathogenic cells is instigated by cytokines. In this review, we describe the main cytokine abnormalities reported in SLE and discuss the mechanisms that drive their aberrant production as well as the pathogenic pathways that their presence promotes.

Interferon alpha as a primary pathogenic factor in human lupus

Interferon alpha (IFN-α) is a critical mediator of human systemic lupus erythematosus (SLE). This review will summarize evidence supporting the role for IFN-α in the initiation of human SLE. IFN-α functions in viral immunity at the interface of innate and adaptive immunity, a position well suited to setting thresholds for autoimmunity. Some individuals treated with IFN-α for chronic viral infections develop de novo SLE, which frequently resolves when IFN-α is withdrawn, supporting the idea that IFN-α was causal. Abnormally high IFN-α levels are clustered within SLE families, suggesting that high serum IFN-α is a heritable risk factor for SLE. Additionally, SLE-risk genetic variants in the IFN-α pathway are gain of function in nature, resulting in either higher circulating IFN-α levels or greater sensitivity to IFN-α signaling in SLE patients. A recent genome-wide association study has identified additional novel genetic loci associated with high serum IFN-α in SLE patients. These data support the idea that genetically determined endogenous elevations in IFN-α predispose to human SLE. It is possible that some of these gain-of-function polymorphisms in the IFN-α pathway are useful in viral defense, and that risk of SLE is a burden we have taken on in the fight to defend ourselves against viral infection.