Strong Association of Combined Genetic Deficiencies in the Classical Complement Pathway With Risk of Systemic Lupus Erythematosus and Primary Sjögren's Syndrome

OBJECTIVE

Complete genetic deficiency of the complement component C2 is a strong risk factor for monogenic systemic lupus erythematosus (SLE), but whether heterozygous C2 deficiency adds to the risk of SLE or primary Sjögren's syndrome (SS) has not been studied systematically. This study was undertaken to investigate potential associations of heterozygous C2 deficiency and C4 copy number variation with clinical manifestations in patients with SLE and patients with primary SS.

METHODS

The presence of the common 28-bp C2 deletion rs9332736 and C4 copy number variation was examined in Scandinavian patients who had received a diagnosis of SLE (n = 958) or primary SS (n = 911) and in 2,262 healthy controls through the use of DNA sequencing. The concentration of complement proteins in plasma and classical complement function were analyzed in a subgroup of SLE patients.

RESULTS

Heterozygous C2 deficiency-when present in combination with a low C4A copy number-substantially increased the risk of SLE (odds ratio [OR] 10.2 [95% confidence interval (95% CI) 3.5-37.0]) and the risk of primary SS (OR 13.0 [95% CI 4.5-48.4]) when compared to individuals with 2 C4A copies and normal C2. For patients heterozygous for rs9332736 with 1 C4A copy, the median age at diagnosis was 7 years earlier in patients with SLE and 12 years earlier in patients with primary SS when compared to patients with normal C2. Reduced C2 levels in plasma (P = 2 × 10^-9 ) and impaired function of the classical complement pathway (P = 0.03) were detected in SLE patients with heterozygous C2 deficiency. Finally, in a primary SS patient homozygous for C2 deficiency, we observed low levels of anti-Scl-70, which suggests a risk of developing systemic sclerosis or potential overlap between primary SS and other systemic autoimmune diseases.

CONCLUSION

We demonstrate that a genetic pattern involving partial deficiencies of C2 and C4A in the classical complement pathway is a strong risk factor for SLE and for primary SS. Our results emphasize the central role of the complement system in the pathogenesis of both SLE and primary SS.

Complement C4 Copy Number Variation is Linked to SSA/Ro and SSB/La Autoantibodies in Systemic Inflammatory Autoimmune Diseases

OBJECTIVE

Copy number variation of the C4 complement components, C4A and C4B, has been associated with systemic inflammatory autoimmune diseases. This study was undertaken to investigate whether C4 copy number variation is connected to the autoimmune repertoire in systemic lupus erythematosus (SLE), primary Sjögren's syndrome (SS), or myositis.

METHODS

Using targeted DNA sequencing, we determined the copy number and genetic variants of C4 in 2,290 well-characterized Scandinavian patients with SLE, primary SS, or myositis and 1,251 healthy controls.

RESULTS

A prominent relationship was observed between C4A copy number and the presence of SSA/SSB autoantibodies, which was shared between the 3 diseases. The strongest association was detected in patients with autoantibodies against both SSA and SSB and 0 C4A copies when compared to healthy controls (odds ratio [OR] 18.0 [95% confidence interval (95% CI) 10.2-33.3]), whereas a weaker association was seen in patients without SSA/SSB autoantibodies (OR 3.1 [95% CI 1.7-5.5]). The copy number of C4 correlated positively with C4 plasma levels. Further, a common loss-of-function variant in C4A leading to reduced plasma C4 was more prevalent in SLE patients with a low copy number of C4A. Functionally, we showed that absence of C4A reduced the individuals' capacity to deposit C4b on immune complexes.

CONCLUSION

We show that a low C4A copy number is more strongly associated with the autoantibody repertoire than with the clinically defined disease entities. These findings may have implications for understanding the etiopathogenetic mechanisms of systemic inflammatory autoimmune diseases and for patient stratification when taking the genetic profile into account.

Genetic and clinical basis for two distinct subtypes of primary Sjögren's syndrome

OBJECTIVES

Clinical presentation of primary Sjögren's syndrome (pSS) varies considerably. A shortage of evidence-based objective markers hinders efficient drug development and most clinical trials have failed to reach primary endpoints.

METHODS

We performed a multicentre study to identify patient subgroups based on clinical, immunological and genetic features. Targeted DNA sequencing of 1853 autoimmune-related loci was performed. After quality control, 918 patients with pSS, 1264 controls and 107 045 single nucleotide variants remained for analysis. Replication was performed in 177 patients with pSS and 7672 controls.

RESULTS

We found strong signals of association with pSS in the HLA region. Principal component analysis of clinical data distinguished two patient subgroups defined by the presence of SSA/SSB antibodies. We observed an unprecedented high risk of pSS for an association in the HLA-DQA1 locus of odds ratio 6.10 (95% CI: 4.93, 7.54, P=2.2×10-62) in the SSA/SSB-positive subgroup, while absent in the antibody negative group. Three independent signals within the MHC were observed. The two most significant variants in MHC class I and II respectively, identified patients with a higher risk of hypergammaglobulinaemia, leukopenia, anaemia, purpura, major salivary gland swelling and lymphadenopathy. Replication confirmed the association with both MHC class I and II signals confined to SSA/SSB antibody positive pSS.

CONCLUSION

Two subgroups of patients with pSS with distinct clinical manifestations can be defined by the presence or absence of SSA/SSB antibodies and genetic markers in the HLA locus. These subgroups should be considered in clinical follow-up, drug development and trial outcomes, for the benefit of both subgroups.

Symptom-based stratification of patients with primary Sjögren's syndrome: multi-dimensional characterisation of international observational cohorts and reanalyses of randomised clinical trials

BACKGROUND

Heterogeneity is a major obstacle to developing effective treatments for patients with primary Sjögren's syndrome. We aimed to develop a robust method for stratification, exploiting heterogeneity in patient-reported symptoms, and to relate these differences to pathobiology and therapeutic response.

METHODS

We did hierarchical cluster analysis using five common symptoms associated with primary Sjögren's syndrome (pain, fatigue, dryness, anxiety, and depression), followed by multinomial logistic regression to identify subgroups in the UK Primary Sjögren's Syndrome Registry (UKPSSR). We assessed clinical and biological differences between these subgroups, including transcriptional differences in peripheral blood. Patients from two independent validation cohorts in Norway and France were used to confirm patient stratification. Data from two phase 3 clinical trials were similarly stratified to assess the differences between subgroups in treatment response to hydroxychloroquine and rituximab.

FINDINGS

In the UKPSSR cohort (n=608), we identified four subgroups: Low symptom burden (LSB), high symptom burden (HSB), dryness dominant with fatigue (DDF), and pain dominant with fatigue (PDF). Significant differences in peripheral blood lymphocyte counts, anti-SSA and anti-SSB antibody positivity, as well as serum IgG, κ-free light chain, β2-microglobulin, and CXCL13 concentrations were observed between these subgroups, along with differentially expressed transcriptomic modules in peripheral blood. Similar findings were observed in the independent validation cohorts (n=396). Reanalysis of trial data stratifying patients into these subgroups suggested a treatment effect with hydroxychloroquine in the HSB subgroup and with rituximab in the DDF subgroup compared with placebo.

INTERPRETATION

Stratification on the basis of patient-reported symptoms of patients with primary Sjögren's syndrome revealed distinct pathobiological endotypes with distinct responses to immunomodulatory treatments. Our data have important implications for clinical management, trial design, and therapeutic development. Similar stratification approaches might be useful for patients with other chronic immune-mediated diseases.

FUNDING

UK Medical Research Council, British Sjogren's Syndrome Association, French Ministry of Health, Arthritis Research UK, Foundation for Research in Rheumatology. VIDEO ABSTRACT.

No structural cerebral MRI changes related to fatigue in patients with primary Sjögren's syndrome

Objective

Whether or not chronic fatigue is reflected in structural changes in the brain is a matter of debate. Primary SS (pSS) is characterized by dryness of the mouth and eyes, migrating muscle and joint pain and prominent fatigue. We aimed to investigate whether the severity of fatigue in pSS was associated with cerebral MRI findings.

Methods

Fatigue was measured with the fatigue visual analog scale in 65 patients with pSS. Global grey matter (GM) and white matter volumes were estimated from magnetic resonance T1 images, and associations between fatigue and brain volumes were assessed in regression models. Voxel-based morphometric analyses of GM were performed to investigate possible associations between fatigue and GM volume changes in particular brain regions.

Results

The fatigue scores in the patient group were spread across a wide range. Global volume analyses showed no significant effect of GM volumes and white matter volumes on fatigue. Voxel-wise analyses of GM did not identify any particular brain region associated with fatigue.

Conclusion

Fatigue is a dominant phenomenon in pSS patients but is not reflected in structural abnormalities in the brain as visualized by conventional MRI. Our findings support the hypothesis of fatigue as a physiological phenomenon that does not lead to vascular changes or neuronal or glial death or damage.

Conventional treatment regimens for ulcerative colitis alleviate fatigue - an observational cohort study

OBJECTIVE

The aim of the study was to investigate the course of fatigue in a conventional inflammatory bowel disease treatment setting.

MATERIALS AND METHODS

Eighty-two patients with newly diagnosed ulcerative colitis were included in an observational cohort study and received conventional non-biological drug treatment for 3 months. Colonoscopy was performed at diagnosis and after 3 months, disease activity was assessed by Mayo score and measurements of serum C-reactive protein (CRP) and fecal calprotectin levels. Fatigue was evaluated using the fatigue visual analog scale (fVAS). Mood was assessed with the hospital anxiety and depression scale (HADS). Associations between fVAS scores and time; age; CRP, fecal calprotectin, hemoglobin, and ferritin levels; and Mayo scores, Mayo endoscopic scores, and HADS depression subscale (HADS-D) scores were explored.

RESULTS

Median fVAS scores decreased, as did Mayo scores and CRP and fecal calprotectin concentrations. HADS-D scores remained unchanged, whereas hemoglobin levels increased after 3 months. Increased fVAS scores were associated with higher ferritin, Mayo and HADS-D scores. There were no associations between fVAS scores and CRP, fecal calprotectin, or Mayo endoscopic scores. Colonic disease distribution did not influence fatigue significantly.

CONCLUSIONS

Disease activity and fatigue improved after 3 months of conventional ulcerative colitis treatment. Over time, more severe fatigue was associated with more ulcerative colitis symptoms, but not with objective disease activity markers or colonic disease distribution. A clinical setting of standard treatment regimens and medical attention may alleviate fatigue in IBD patients.

Fatigue in Newly Diagnosed Inflammatory Bowel Disease

BACKGROUND AND AIMS

The present study investigated the prevalence and severity of fatigue in patients with newly diagnosed and untreated ulcerative colitis (UC) and Crohn's disease (CD) and examined relevant disease variables that may influence the severity of fatigue.

METHODS

Eighty-one patients with inflammatory bowel disease (IBD) (60 with UC and 21 with CD) were assessed for fatigue using two fatigue instruments: the Fatigue Severity Scale (FSS) and a fatigue visual analogue scale (fVAS). Cut-off for fatigue was defined as ≥4 for FSS and ≥50 for fVAS. Results were compared with fatigue scores from age-and gender-matched healthy individuals. Disease activity was assessed by symptom scores using the Mayo score in UC patients and the Harvey-Bradshaw index for CD patients, as well as C-reactive protein (CRP) and faecal calprotectin.

RESULTS

The prevalence of fatigue based on FSS and fVAS was 47 and 42%, respectively, in UC and 62 and 48% in CD. In multivariate regression models, disease activity markers were not associated with fatigue, while a significant relationship was found with age and depression for both fatigue measures.

CONCLUSIONS

Close to 50% of patients with IBD reported fatigue at the time of diagnosis. In newly diagnosed patients with active disease, the severity of fatigue was not associated with measures of disease activity.

Improved detection of advanced oxidation protein products in plasma

BACKGROUND

Oxidative stress has been associated with many diseases and can among others be assessed as increased levels of advanced oxidation protein products (AOPP). Current AOPP methods suffer from poor reproducibility and accuracy due to precipitation of lipids in plasma samples. We therefore aimed to develop a robust method in which plasma lipids are solubilized.

METHODS

Plasma was diluted with citric acid, and AOPP measured as absorbance at 340 nm. The method was optimized and validated, and then used to analyze AOPP levels in plasma from healthy control subjects (HC), and in three patients groups; chronic kidney disease (CKD), primary Sjögren's Syndrome (pSS) and systemic lupus erythematosus (SLE).

RESULTS

AOPP was detected with improved precision compared to established methods where lipids precipitate. Within- and between days variations were less than 1.4% and 2.2%, respectively. A control chart was established and the long-term reproducibility followed over six months.

CONCLUSIONS

This improved method detects plasma AOPP with significantly better reproducibility and accuracy compared to previously reported methods. Solubilization of plasma lipids before spectrophotometric measure of AOPP levels is novel. It prevents both loss of lipoproteins due to precipitation and overestimation as a result of light scattering.