A survey of ficolin-3 activity in Systemic Lupus Erythematosus reveals a link to hematological disease manifestations and autoantibody profile.

The complement system plays a central role in the pathogenesis of Systemic Lupus Erythematosus (SLE), but most studies have focused on the classical pathway. Ficolin-3 is the main initiator of the lectin pathway of complement in humans, but its role in systemic autoimmune disease has not been conclusively determined. Here, we combined biochemical and genetic approaches to assess the contribution of ficolin-3 to SLE risk and disease manifestations. Ficolin-3 activity was measured by a functional assay in serum or plasma samples from Swedish SLE patients (n = 786) and controls matched for age and sex (n = 566). Genetic variants in an extended 300 kb genomic region spanning the FCN3 locus were analyzed for their association with ficolin-3 activity and SLE manifestations in a Swedish multicenter cohort (n = 985). Patients with ficolin-3 activity in the highest tertile showed a strong enrichment in an SLE cluster defined by anti-Sm/DNA/nucleosome antibodies (OR 3.0, p < 0.001) and had increased rates of hematological disease (OR 1.4, p = 0.078) and lymphopenia (OR = 1.6, p = 0.039). Genetic variants associated with low ficolin-3 activity mapped to an extended haplotype in high linkage disequilibrium upstream of the FCN3 gene. Patients carrying the lead genetic variant associated with low ficolin-3 activity had a lower frequency of hematological disease (OR 0.67, p = 0.018) and lymphopenia (OR 0.63, p = 0.031) and fewer autoantibodies (p = 0.0019). Loss-of-function variants in the FCN3 gene were not associated with SLE, but four (0.5 %) SLE patients developed acquired ficolin-3 deficiency where ficolin-3 activity in serum was depleted following diagnosis of SLE. Taken together, our results provide genetic and biochemical evidence that implicate the lectin pathway in hematological SLE manifestations. We also identify lectin pathway activation through ficolin-3 as a factor that contributes to the autoantibody response in SLE.

Plasma interferon-alpha protein levels during pregnancy are associated with lower birth weight in systemic lupus erythematosus.

OBJECTIVES: Adverse pregnancy outcomes are more common in women with systemic lupus erythematosus (SLE) compared with healthy women, but we lack prognostic biomarkers. Plasma interferon alpha (IFNα) protein levels are elevated in a subgroup of pregnant women with SLE, but whether this is associated with pregnancy outcomes is unknown. We investigated the relationship between IFNα, adverse pregnancy outcomes and the presence of autoantibodies in SLE pregnancy. METHODS: We followed 76 women with SLE prospectively. Protein levels of IFNα were quantified in plasma collected in the 2nd and 3rd trimester with single-molecule array. Positivity for antinuclear and antiphospholipid antibodies was assessed during late pregnancy with multiplexed bead assay. Clinical outcomes included the adverse pregnancy outcomes small for gestational age (SGA), preterm birth, and preeclampsia. RESULTS: During SLE pregnancy, women with SGA infants compared with those without had higher levels of plasma IFNα protein, and IFNα positivity was associated with lower birth weight of the infant. Preterm birth was associated with autoantibodies against chromatin. IFNα protein levels associated positively with autoantibodies against chromatin, Smith/ribonucleoprotein (SmRNP) and RNP, but negatively with phospholipid antibodies. CONCLUSION: Elevated IFNα protein in plasma of women with SLE is a potential risk factor for lower birth weight of their infants. The association between IFNα and lower birth weight warrants further investigation regarding the pathophysiological role of IFNα during SLE pregnancy.

Serologic immunogenicity and safety of Herpes Zoster subunit vaccine in patients with Rheumatoid Arthritis receiving Janus Kinase inhibitors.

OBJECTIVE: Patients with rheumatoid arthritis (RA) treated with Janus Kinase inhibitors (JAKi) are at increased risk of Herpes Zoster (HZ). The objective of this study was to investigate serological immunogenicity and safety of the HZ subunit (HZ/su) vaccine in RA patients treated with JAKi, for which little is known. METHODS: RA patients treated with JAKi (n = 82) at the Department of Rheumatology, Skåne University Hospital, Sweden, and healthy controls (n = 51) received two doses of the HZ/su vaccine (Shingrix). Vaccine-specific antibody responses were analysed using indirect enzyme-linked immunosorbent assay (ELISA). Post-vaccination antibody levels were compared between patients and controls using analysis of covariance. Potential predictors for vaccine response were investigated using a multivariable linear regression analysis. Self-reported adverse events (AEs) and changes in RA disease activity were analysed. RESULTS: Following vaccination, vaccine-specific antibody levels increased significantly in both patients and controls (p< 0.0001). 80.5% of patients and 98.0% of controls achieved a ≥ 4-fold increase in antibody levels. Post-vaccination antibody levels were lower in patients than controls (ratio 0.44, 95% CI 0.31-0.63), and lower in patients receiving JAKi+Methotrexate than JAKi monotherapy (ratio 0.43, 95% CI 0.24-0.79). AEs, mostly mild/moderate, were common. One patient developed HZ and six patients (6.5%) had increased RA disease activity following vaccination. CONCLUSION: The HZ/su vaccine was serologically immunogenic in most RA patients treated with JAKi. Moreover, the vaccine had an acceptable safety profile. These results support recommendations for usage of the HZ/su vaccine in this vulnerable population. TRIAL REGISTRATION: ClinicalTrials.gov, https://clinicaltrials.gov, NCT03886038.

Argonaute, Vault, and Ribosomal Proteins Targeted by Autoantibodies in Systemic Lupus Erythematosus.

OBJECTIVE: To expand, in an unbiased manner, our knowledge of autoantigens and autoantibodies in patients with systemic lupus erythematosus (SLE) and evaluate their associations with serological and clinical variables. METHODS: Human proteome arrays (> 21,000 proteins) were screened with serum from patients with SLE (n = 12) and healthy controls (n = 6) for IgG and IgA binding. Top hits were validated with 2 cohorts of patients with SLE (cohort 1, n = 49; cohort 2, n = 46) and other rheumatic diseases by ELISA. Clinical associations of the autoantibodies were tested. RESULTS: Ro60 was the top hit in the screen, and the 10 following proteins included 2 additional known SLE autoantigens plus 8 novel autoantigens involved in microRNA processing (Argonaute protein 1 [AGO1], AGO2, and AGO3), ribosomes (ribosomal protein lateral stalk subunit P2 and ovarian tumor deubiquitinase 5 [OTUD5]), RNA transport by the vault (major vault protein), and the immune proteasome (proteasome activator complex subunit 3). Patient serum contained IgG reactive with these proteins and IgA against the AGO proteins. Using the 95th percentile of healthy donor reactivity, 5-43% were positive for the novel antigens, with OTUD5 and AGO1 showing the highest percentages of positivity. Autoantibodies against AGO1 proteins were more prevalent in patients with oral ulcers in a statistically significant manner. IgG autoantibodies against AGO proteins were also seen in other rheumatic diseases. CONCLUSION: We discovered new autoantigens existing in cytosolic macromolecular protein assemblies containing RNA (except the proteasome) in cells. A more comprehensive list of autoantigens will allow for a better analysis of how proteins are targeted by the autoimmune response. Future research will also reveal whether specific autoantibodies have utility in the diagnosis or management of SLE.

Autoantibodies against the envelope proteins of endogenous retroviruses K102 and K108 in patients with systemic lupus erythematosus correlate with active disease.

OBJECTIVES: To determine if patients with systemic lupus erythematosus (SLE), a disease characterised by elevated type I interferons reminiscent of anti-viral immunity, have expression of human endogenous retrovirus K (HERV-K) proviruses capable of producing envelope (Env) protein, as well as associated autoantibodies against the Env protein. METHODS: ELISAs were conducted with recombinant Env protein and sera from SLE patients with active (n=60) or inactive (n=49) disease, healthy controls (n=47), other rheumatic disorders (n=59), as well as plasma from paediatric lupus patients with active (n=30) or inactive (n=30) disease, and 17 healthy children. Antibody reactivity was evaluated for correlations with clinical and laboratory parameters of the patients. Expression of HERV-K transcripts were profiled in SLE leukocytes by RNA-Seq. RESULTS: Both adult and paediatric SLE patients had autoantibodies against HERV-K Env with higher titres than healthy controls or patients with Sjögren's syndrome, small- or large-vessel vasculitis, or psoriatic arthritis. Transcripts from only two HERV-K loci capable of producing Env, HERV-K102 and -K108, were detected among the 10 expressed loci in SLE patients. CONCLUSIONS: Our data reveal that HERV-K proviruses are expressed in SLE and that the HERV-K-encoded Env protein elicits an immune response in patients, particularly during active disease.

Plasma and cerebrospinal fluid neurofilament light concentrations reflect neuronal damage in systemic lupus Erythematosus.

BACKGROUND: Neuronal damage in systemic lupus erythematosus (SLE) is common, but the extent and mechanisms are unclear. Neurofilament light (NfL) concentrations rise in plasma and cerebrospinal fluid (CSF) during neuronal damage in various neurological disorders. In this cross-sectional study, plasma and CSF concentrations of NfL were explored as a marker of neuronal damage in SLE. METHODS: Seventy-two consecutive SLE out-patients and 26 healthy controls, all female, aged < 55 years, underwent magnetic resonance imaging (MRI) and neurocognitive testing. NfL concentrations in plasma from all individuals and in CSF from 32 patients were measured with single-molecule array technology. Patients were assessed by a rheumatologist and neurologist to define neuropsychiatric involvement (NPSLE) according to three attribution models: SLICC A, SLICC B and ACR. RESULTS: Plasma and CSF NfL concentrations correlated strongly (r = 0.72, p < 0.001). Both NPSLE and non-NPSLE patients in all attribution models had higher plasma NfL concentrations compared with healthy controls (log-NfL, pg/ml, mean (SD); healthy controls (0.71 (0.17)); SLICC A model: NPSLE (0.87 (0.13), p = 0.003), non-NPSLE (0.83 (0.18), p = 0.005); SLICC B model: NPSLE (0.87 (0.14), p = 0.001), non-NPSLE (0.83 (0.18), p = 0.008); ACR model: NPSLE (0.86 (0.16), p < 0.001), non-NPSLE (0.81 (0.17), p = 0.044)). Plasma and CSF NfL concentrations did not differ between NPSLE and non-NPSLE patients. Higher plasma NfL concentrations correlated with larger CSF volumes on MRI (r = 0.34, p = 0.005), and was associated with poorer cognitive performance in the domains of simple attention, psychomotor speed and verbal memory. SLICC/ACR-Damage Index ≥1 was independently associated with higher plasma NfL concentrations (ß = 0.074, p = 0.038). Higher plasma creatinine concentrations, anti-dsDNA-positivity, low complement C3 levels, or a history of renal involvement were associated with higher plasma NfL concentrations (ß = 0.003, p = 0.009; ß = 0.072, p = 0.031; ß = 0.077, p = 0.027; ß = 0.069, p = 0.047, respectively). CONCLUSIONS: Higher plasma NfL concentrations in NPSLE and non-NPSLE patients may indicate a higher degree of neuronal damage in SLE in general, corresponding to cognitive impairment and organ damage development. Furthermore, our results may indicate a higher degree of neuronal breakdown in patients with active SLE, also without overt clinical symptoms. NfL may serve as an indicator of neuronal damage in SLE in further studies.

Variants in BANK1 are associated with lupus nephritis of European ancestry.

The genetic background of lupus nephritis (LN) has not been completely elucidated. We performed a case-only study of 2886 SLE patients, including 947 (33%) with LN. Renal biopsies were available from 396 patients. The discovery cohort (Sweden, n = 1091) and replication cohort 1 (US, n = 962) were genotyped on the Immunochip and replication cohort 2 (Denmark/Norway, n = 833) on a custom array. Patients with LN, proliferative nephritis, or LN with end-stage renal disease were compared with SLE without nephritis. Six loci were associated with LN (p < 1 × 10-4, NFKBIA, CACNA1S, ITGA1, BANK1, OR2Y, and ACER3) in the discovery cohort. Variants in BANK1 showed the strongest association with LN in replication cohort 1 (p = 9.5 × 10-4) and proliferative nephritis in a meta-analysis of discovery and replication cohort 1. There was a weak association between BANK1 and LN in replication cohort 2 (p = 0.052), and in the meta-analysis of all three cohorts the association was strengthened (p = 2.2 × 10-7). DNA methylation data in 180 LN patients demonstrated methylation quantitative trait loci (meQTL) effects between a CpG site and BANK1 variants. To conclude, we describe genetic variations in BANK1 associated with LN and evidence for genetic regulation of DNA methylation within the BANK1 locus. This indicates a role for BANK1 in LN pathogenesis.

Proteomic Data Analysis for Differential Profiling of the Autoimmune Diseases SLE, RA, SS, and ANCA-Associated Vasculitis.

Early and correct diagnosis of inflammatory rheumatic diseases (IRD) poses a clinical challenge due to the multifaceted nature of symptoms, which also may change over time. The aim of this study was to perform protein expression profiling of four systemic IRDs, systemic lupus erythematosus (SLE), ANCA-associated systemic vasculitis (SV), rheumatoid arthritis (RA), and Sjögren's syndrome (SS), and healthy controls to identify candidate biomarker signatures for differential classification. A total of 316 serum samples collected from patients with SLE, RA, SS, or SV and from healthy controls were analyzed using 394-plex recombinant antibody microarrays. Differential protein expression profiling was examined using Wilcoxon signed rank test, and condensed biomarker panels were identified using advanced bioinformatics and state-of-the art classification algorithms to pinpoint signatures reflecting each disease (raw data set available at https://figshare.com/s/3bd3848a28ef6e7ae9a9.). In this study, we were able to classify the included individual IRDs with high accuracy, as demonstrated by the ROC area under the curve (ROC AUC) values ranging between 0.96 and 0.80. In addition, the groups of IRDs could be separated from healthy controls at an ROC AUC value of 0.94. Disease-specific candidate biomarker signatures and general autoimmune signature were identified, including several deregulated analytes. This study supports the rationale of using multiplexed affinity-based technologies to reflect the biological complexity of autoimmune diseases. A multiplexed approach for decoding multifactorial complex diseases, such as autoimmune diseases, will play a significant role for future diagnostic purposes, essential to prevent severe organ- and tissue-related damage.

Interaction between the STAT4 rs11889341(T) risk allele and smoking confers increased risk of myocardial infarction and nephritis in patients with systemic lupus erythematosus.

OBJECTIVE: To investigate how genetics influence the risk of smoking-related systemic lupus erythematosus (SLE) manifestations. METHODS: Patients with SLE (ndiscovery cohort=776, nreplication cohort=836) were genotyped using the 200K Immunochip single nucleotide polymorphisms (SNP) Array (Illumina) and a custom array. Sixty SNPs with SLE association (p<5.0×10-8) were analysed. Signal transducer and activator of transcription 4 (STAT4) activation was assessed in in vitro stimulated peripheral blood mononuclear cells from healthy controls (n=45). RESULTS: In the discovery cohort, smoking was associated with myocardial infarction (MI) (OR 1.96 (95% CI 1.09 to 3.55)), with a greater effect in patients carrying any rs11889341 STAT4 risk allele (OR 2.72 (95% CI 1.24 to 6.00)) or two risk alleles (OR 8.27 (95% CI 1.48 to 46.27)).Smokers carrying the risk allele also displayed an increased risk of nephritis (OR 1.47 (95% CI 1.06 to 2.03)). In the replication cohort, the high risk of MI in smokers carrying the risk allele and the association between the STAT4 risk allele and nephritis in smokers were confirmed (OR 6.19 (95% CI 1.29 to 29.79) and 1.84 (95% CI 1.05 to 3.29), respectively).The interaction between smoking and the STAT4 risk allele resulted in further increase in the risk of MI (OR 2.14 (95% CI 1.01 to 4.62)) and nephritis (OR 1.53 (95% CI 1.08 to 2.17)), with 54% (MI) and 34% (nephritis) of the risk attributable to the interaction. Levels of interleukin-12-induced phosphorylation of STAT4 in CD8+ T cells were higher in smokers than in non-smokers (mean geometric fluorescence intensity 1063 vs 565, p=0.0063).Lastly, the IL12A rs564799 risk allele displayed association with MI in both cohorts (OR 1.53 (95% CI 1.01 to 2.31) and 2.15 (95% CI 1.08 to 4.26), respectively). CONCLUSIONS: Smoking in the presence of the STAT4 risk gene variant appears to increase the risk of MI and nephritis in SLE. Our results also highlight the role of the IL12-STAT4 pathway in SLE-cardiovascular morbidity.

Molecular pathways in patients with systemic lupus erythematosus revealed by gene-centred DNA sequencing.

OBJECTIVES: Systemic lupus erythematosus (SLE) is an autoimmune disease with extensive heterogeneity in disease presentation between patients, which is likely due to an underlying molecular diversity. Here, we aimed at elucidating the genetic aetiology of SLE from the immunity pathway level to the single variant level, and stratify patients with SLE into distinguishable molecular subgroups, which could inform treatment choices in SLE. METHODS: We undertook a pathway-centred approach, using sequencing of immunological pathway genes. Altogether 1832 candidate genes were analysed in 958 Swedish patients with SLE and 1026 healthy individuals. Aggregate and single variant association testing was performed, and we generated pathway polygenic risk scores (PRS). RESULTS: We identified two main independent pathways involved in SLE susceptibility: T lymphocyte differentiation and innate immunity, characterised by HLA and interferon, respectively. Pathway PRS defined pathways in individual patients, who on average were positive for seven pathways. We found that SLE organ damage was more pronounced in patients positive for the T or B cell receptor signalling pathways. Further, pathway PRS-based clustering allowed stratification of patients into four groups with different risk score profiles. Studying sets of genes with priors for involvement in SLE, we observed an aggregate common variant contribution to SLE at genes previously reported for monogenic SLE as well as at interferonopathy genes. CONCLUSIONS: Our results show that pathway risk scores have the potential to stratify patients with SLE beyond clinical manifestations into molecular subsets, which may have implications for clinical follow-up and therapy selection.

De novo lupus nephritis during treatment with belimumab.

OBJECTIVE: In light of reports of de novo LN during belimumab (BLM) treatment, we sought to determine its frequency and contributing or protective factors in a real-life setting. METHODS: Patients with SLE who received BLM between 2011 and 2017 at five European academic practices were enrolled (n = 95) and followed longitudinally for a median time of 13.1 months [interquartile range (IQR): 6.0-34.7]; 52.6% were anti-dsDNA positive, 60.0% had low complement levels, and 69.5% had no renal involvement prior to/at BLM initiation [mean disease duration at baseline: 11.4 (9.3) years]. Age- and sex-matched patients with non-renal SLE who had similar serological profiles, but were not exposed to BLM, served as controls (median follow-up: 132.0 months; IQR: 98.3-151.2). RESULTS: We observed 6/66 cases (9.1%) of biopsy-proven de novo LN (4/6 proliferative) among the non-renal BLM-treated SLE cases after a follow-up of 7.4 months (IQR: 2.7-22.2). Among controls, 2/66 cases (3.0%) of de novo LN (both proliferative) were observed after 21 and 50 months. BLM treatment was associated with an increased frequency and/or shorter time to de novo LN [hazard ratio (HR): 10.7; 95% CI: 1.7, 67.9; P = 0.012], while concomitant use of antimalarial agents along with BLM showed an opposing association (HR: 0.2; 95% CI: 0.03, 0.97; P = 0.046). CONCLUSION: Addition of BLM to standard-of-care did not prevent LN in patients with active non-renal SLE, but a favourable effect of concomitant use of antimalarials was implicated. Studies of whether effects of B-cell activating factor inhibition on lymphocyte subsets contribute to LN susceptibility are warranted.

Complement deposition, C4d, on platelets is associated with vascular events in systemic lupus erythematosus.

OBJECTIVE: Complement components, including C4d, can be found on activated platelets, a process associated with vascular disease in SLE. We investigated whether platelet C4d (PC4d) adds additional value to traditional and known lupus-associated risk factors when identifying SLE patients with vascular disease. METHODS: This cross-sectional study included 308 well-characterized SLE patients and 308 matched general population controls. PC4d deposition was analysed using flow cytometry. Values >95% of controls were considered as PC4d positive (+). aPL were determined by Luminex, and the LA test was performed by DRVVT. History of vascular disease (composite and as separate outcomes) was defined at inclusion. RESULTS: SLE patients had increased PC4d deposition as compared with population controls (50 vs 5%, P < 0.0001). PC4d+ positively associated with any vascular events, and separately with venous and cerebrovascular events, and also with all investigated aPL profiles. The association for any vascular event remained statistically significant after adjustment for traditional and SLE-associated risk factors (odds ratio: 2.3, 95% CI: 1.3, 4.3, P = 0.008). Compared with patients negative for both PC4d and LA, patients with double positivity were more likely to have vascular disease (odds ratio: 12.3, 95% CI: 5.4, 29.3; attributable proportion due to interaction 0.8, 95% CI: 0.4, 1.1). CONCLUSION: PC4d+ is associated with vascular events in SLE, independently of traditional and SLE-associated risk factors. Concurrent presence of PC4d and LA seem to interact to further increase the odds for vascular events. Prospective studies should examine whether the aPL/PC4d combination can improve prediction of vascular events in SLE and/or APS.

Autoantibody and Cytokine Profiles during Treatment with Belimumab in Patients with Systemic Lupus Erythematosus.

We investigated whether belimumab treatment impacts on levels of autoantibodies and cytokines of interest in systemic lupus erythematosus (SLE). Longitudinally collected serum samples from 78 belimumab-treated Swedish SLE patients were analysed. Serum cytokine levels were determined using Luminex xMAP technology, and nuclear antigen autoantibody specificities using addressable laser bead immunoassay. In patients with detectable levels at baseline, interferon (IFN)-α2 levels were lower at month 6 (median; interquartile range (IQR): 8.9; 1.5-54.9 pg/mL) versus baseline (28.4; 20.9-100.3 pg/mL; p = 0.043). Interleukin (IL)-6 (baseline: 7.1; 2.9-16.1 pg/mL) decreased from month 6 (0.5; 0.5-6.3 pg/mL; p = 0.018) and throughout a 24 month follow-up. IL-10 (baseline: 12.6; 2.8-29.7 pg/mL) showed more rapid decreases from month 3 (1.8; 0.6-9.1 pg/mL; p = 0.003). Levels of anti-dsDNA (p < 0.001), anti-Smith antigen (Sm) (p = 0.002), anti-U1 small nuclear ribonucleoprotein (U1RNP) (p < 0.001), anti-Sm-U1RNP complex (p = 0.028), and anti-ribosomal P (p = 0.012) antibodies decreased from month 3 and remained decreased. Anti-Sm positivity at baseline was associated with higher probability and/or shorter time to achieve sustained SLE responder index-4 response (hazard ratio (HR): 2.52; 95% CI: 1.20-5.29; p = 0.015), independently of other factors. Decline of IL-6 levels through month 3 was greater in responders. In summary, belimumab treatment lowered IFN-α2, IL-6, and IL-10 levels, as well as levels of multiple autoantibodies, however after different time spans. Notably, anti-Sm positivity and early decline in IL-6 levels were associated with favorable treatment outcome.

Whole-genome sequencing identifies complex contributions to genetic risk by variants in genes causing monogenic systemic lupus erythematosus.

Systemic lupus erythematosus (SLE, OMIM 152700) is a systemic autoimmune disease with a complex etiology. The mode of inheritance of the genetic risk beyond familial SLE cases is currently unknown. Additionally, the contribution of heterozygous variants in genes known to cause monogenic SLE is not fully understood. Whole-genome sequencing of DNA samples from 71 Swedish patients with SLE and their healthy biological parents was performed to investigate the general genetic risk of SLE using known SLE GWAS risk loci identified using the ImmunoChip, variants in genes associated to monogenic SLE, and the mode of inheritance of SLE risk alleles in these families. A random forest model for predicting genetic risk for SLE showed that the SLE risk variants were mainly inherited from one of the parents. In the 71 patients, we detected a significant enrichment of ultra-rare ( ≤ 0.1%) missense and nonsense mutations in 22 genes known to cause monogenic forms of SLE. We identified one previously reported homozygous nonsense mutation in the C1QC (Complement C1q C Chain) gene, which explains the immunodeficiency and severe SLE phenotype of that patient. We also identified seven ultra-rare, coding heterozygous variants in five genes (C1S, DNASE1L3, DNASE1, IFIH1, and RNASEH2A) involved in monogenic SLE. Our findings indicate a complex contribution to the overall genetic risk of SLE by rare variants in genes associated with monogenic forms of SLE. The rare variants were inherited from the other parent than the one who passed on the more common risk variants leading to an increased genetic burden for SLE in the child. Higher frequency SLE risk variants are mostly passed from one of the parents to the offspring affected with SLE. In contrast, the other parent, in seven cases, contributed heterozygous rare variants in genes associated with monogenic forms of SLE, suggesting a larger impact of rare variants in SLE than hitherto reported.

DNA methylation mapping identifies gene regulatory effects in patients with systemic lupus erythematosus.

OBJECTIVES: Systemic lupus erythematosus (SLE) is a chronic autoimmune condition with heterogeneous presentation and complex aetiology where DNA methylation changes are emerging as a contributing factor. In order to discover novel epigenetic associations and investigate their relationship to genetic risk for SLE, we analysed DNA methylation profiles in a large collection of patients with SLE and healthy individuals. METHODS: DNA extracted from blood from 548 patients with SLE and 587 healthy controls were analysed on the Illumina HumanMethylation 450 k BeadChip, which targets 485 000 CpG sites across the genome. Single nucleotide polymorphism (SNP) genotype data for 196 524 SNPs on the Illumina ImmunoChip from the same individuals were utilised for methylation quantitative trait loci (cis-meQTLs) analyses. RESULTS: We identified and replicated differentially methylated CpGs (DMCs) in SLE at 7245 CpG sites in the genome. The largest methylation differences were observed at type I interferon-regulated genes which exhibited decreased methylation in SLE. We mapped cis-meQTLs and identified genetic regulation of methylation levels at 466 of the DMCs in SLE. The meQTLs for DMCs in SLE were enriched for genetic association to SLE, and included seven SLE genome-wide association study (GWAS) loci: PTPRC (CD45), MHC-class III, UHRF1BP1, IRF5, IRF7, IKZF3 and UBE2L3. In addition, we observed association between genotype and variance of methylation at 20 DMCs in SLE, including at the HLA-DQB2 locus. CONCLUSIONS: Our results suggest that several of the genetic risk variants for SLE may exert their influence on the phenotype through alteration of DNA methylation levels at regulatory regions of target genes.

Novel gene variants associated with cardiovascular disease in systemic lupus erythematosus and rheumatoid arthritis.

OBJECTIVES: Patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) have increased risk of cardiovascular disease (CVD). We investigated whether single nucleotide polymorphisms (SNPs) at autoimmunity risk loci were associated with CVD in SLE and RA. METHODS: Patients with SLE (n=1045) were genotyped using the 200K Immunochip SNP array (Illumina). The allele frequency was compared between patients with and without different manifestations of CVD. Results were replicated in a second SLE cohort (n=1043) and in an RA cohort (n=824). We analysed publicly available genetic data from general population, performed electrophoretic mobility shift assays and measured cytokine levels and occurrence of antiphospholipid antibodies (aPLs). RESULTS: We identified two new putative risk loci associated with increased risk for CVD in two SLE populations, which remained after adjustment for traditional CVD risk factors. An IL19 risk allele, rs17581834(T) was associated with stroke/myocardial infarction (MI) in SLE (OR 2.3 (1.5 to 3.4), P=8.5×10-5) and RA (OR 2.8 (1.4 to 5.6), P=3.8×10-3), meta-analysis (OR 2.5 (2.0 to 2.9), P=3.5×10-7), but not in population controls. The IL19 risk allele affected protein binding, and SLE patients with the risk allele had increased levels of plasma-IL10 (P=0.004) and aPL (P=0.01). An SRP54-AS1 risk allele, rs799454(G) was associated with stroke/transient ischaemic attack in SLE (OR 1.7 (1.3 to 2.2), P=2.5×10-5) but not in RA. The SRP54-AS1 risk allele is an expression quantitative trait locus for four genes. CONCLUSIONS: The IL19 risk allele was associated with stroke/MI in SLE and RA, but not in the general population, indicating that shared immune pathways may be involved in the CVD pathogenesis in inflammatory rheumatic diseases.

A single nucleotide polymorphism in the NCF1 gene leading to reduced oxidative burst is associated with systemic lupus erythematosus.

OBJECTIVES: Ncf1 polymorphisms leading to low production of reactive oxygen species (ROS) are strongly associated with autoimmune diseases in animal models. The human NCF1 gene is very complex with both functional and non-functional gene copies and genotyping requires assays specific for functional NCF1 genes. We aimed at investigating association and function of the missense single nucleotide polymorphism (SNP), rs201802880 (here denoted NCF1-339) in NCF1 with systemic lupus erythematosus (SLE). METHODS: We genotyped the NCF1-339 SNP in 973 Swedish patients with SLE and 1301 controls, using nested PCR and pyrosequencing. ROS production and gene expression of type 1 interferon-regulated genes were measured in isolated cells from subjects with different NCF1-339 genotypes. RESULTS: We found an increased frequency of the NCF1-339 T allele in patients with SLE, 11% compared with 4% in controls, OR 3.0, 95% CI 2.4 to 3.9, p=7.0×10-20. The NCF1-339 T allele reduced extracellular ROS production in neutrophils (p=0.004) and led to an increase expression of type 1 interferon-regulated genes. In addition, the NCF1-339 T allele was associated with a younger age at diagnosis of SLE; mean age 30.3 compared with 35.9, p=2.0×1-6. CONCLUSIONS: These results clearly demonstrate that a genetically controlled reduced production of ROS increases the risk of developing SLE and confirm the hypothesis that ROS regulate chronic autoimmune inflammatory diseases.

Decreased platelet size is associated with platelet activation and anti-phospholipid syndrome in systemic lupus erythematosus.

Objectives: . SLE is an autoimmune disease with increased cardiovascular morbidity and platelet activation. In the general population, increased platelet size predicts platelet reactivity and cardiovascular disease. The aim of this study was to investigate whether platelet size related to platelet activation and cardiovascular disease in SLE. Methods: . Fresh blood samples from SLE patients ( n = 148), healthy volunteers ( n = 79) and disease controls ( n = 40) were analysed for platelet size and activation by flow cytometry, ELISA and cell count. Associations to manifest cardiovascular disease, venous thrombosis and APS were adjusted for traditional cardiovascular risk factors using logistic regression analysis. Results: . SLE patients had decreased platelet size as compared with healthy controls ( P = 0.003). In SLE, decreased platelet size was related to increased platelet activation, in particular microparticle formation ( P < 0.0001, r = -0.46) and release of serotonin from dense granules ( P < 0.001, r = 0.57). SLE patients with aCL had decreased platelet size ( P = 0.02) and aCL decreased platelet size in vitro ( P = 0.007). In contrast to the general population, increased platelet size was not associated with cardiovascular disease. Instead, decreased platelet size was associated with secondary APS, even after adjusting for traditional cardiovascular risk factors ( P = 0.01, odds ratio 3.58). Conclusion: . Platelet size is decreased in SLE patients and associated with microparticle formation and APS. Future studies are needed to determine the underlying mechanism(s) as well as the potential predictive value of small platelets for disease complications in SLE.

A novel mechanism for NETosis provides antimicrobial defense at the oral mucosa.

Neutrophils are essential for host defense at the oral mucosa and neutropenia or functional neutrophil defects lead to disordered oral homeostasis. We found that neutrophils from the oral mucosa harvested from morning saliva had released neutrophil extracellular traps (undergone NETosis) in vivo. The NETosis was mediated through intracellular signals elicited by binding of sialyl Lewis(X) present on salival mucins to l-selectin on neutrophils. This led to rapid loss of nuclear membrane and intracellular release of granule proteins with subsequent neutrophil extracellular trap (NET) release independent of elastase and reduced NAD phosphate-oxidase activation. The saliva-induced NETs were more DNase-resistant and had higher capacity to bind and kill bacteria than NETs induced by bacteria or by phorbol-myristate acetate. Furthermore, saliva/sialyl Lewis(X) mediated signaling enhanced intracellular killing of bacteria by neutrophils. Saliva from patients with aphthous ulcers and Behçet disease prone to oral ulcers failed to induce NETosis, but for different reasons it demonstrated that disordered homeostasis in the oral cavity may result in deficient saliva-mediated NETosis.