Serum complement 3 is a potential biomarker for assessing disease activity in Takayasu arteritis

A pilot study of childhood-onset Takayasu arteritis using whole exome sequencing suggests oligogenic inheritance involving classical complement, collagen, and autoinflammatory pathways

Takayasu arteritis (TA) is a chronic granulomatous inflammatory disease affecting the aorta and its branches. Paediatric TA (pTA) may present from 6 months after birth till the adolescent age group. Genetics and pathogenesis of pTA are not fully understood. Earlier studies reported monogenic mutation in NOD2, XIAP, and STAT1 genes in patients with pTA. TA, a relatively rare disease, is more common in geographical pockets, including India. We hypothesized that South Asian patients with pTA, namely, those of Indian subcontinent origin, may have clinically relevant and unique pathogenic variants involving one or more genes, especially those linked to genetically driven vasculitic illnesses, including autoinflammatory pathologies. Children with pTA fulfilling EULAR/PRINTO/PReS classification criteria and presenting with clinical symptoms to the Paediatric Rheumatology clinic of Christian Medical College, Vellore, were included. Blood samples were collected after getting informed consent from parents or guardians and assent forms from children. DNA was extracted from whole blood using the Qiagen DNA extraction kit. Initially, the common variant in Indian population, namely, ADA2 c.139G > A; p.Gly47Arg, was screened, followed by whole exome sequencing. Fourteen children were recruited for the study. Median age of patients was 11 years (4 months-14 years) with a male-to-female ratio of 4:10. Distribution of angiographic subsets by Numano's classification of included children were as follows: type 5 (n = 7), type 4 (n = 5), and type 3 (n = 2). We identified novel variants in ten different genes. This include variants in genes of classical complement pathway, namely, C2, C3, C6, C7, and C9, and other genes, namely, CYBA, SH3BP2, GUCY2C, CTC1, COL5A1, and NLPR3. Two of 14 patients have heterozygous pathogenic variants; this implies that combination of heterozygous variants in C3 and COL5A1 might lead to disease development, suggesting digenic inheritance. One patient has a homozygous variant in CYBA. None of the patients were identified to have ADA2 variants. Whole exome sequencing reveals combination of rare variants in genes C3, COL5A1, and CYBA associated with disease development in children with Takayasu Arteritis. Key Points • We identified novel variants in genes of classical complement pathway, namely, C2, C3, C6, C7, and C9, and other genes, namely, CYBA, SH3BP2, GUCY2C, CTC1, COL5A1, and NLPR3. • Two of 14 patients have heterozygous pathogenic variants in C3 and COL5A1; this may have implications in disease development, suggesting digenic inheritance. • One patient has homozygous variant in CYBA. • None of the patients were identified to have ADA2 variants.

Interleukin 6 Levels and Disease Activity in Takayasu Arteritis: A Systematic Review With Meta-analysis

BACKGROUND

Various studies have suggested interleukin 6 (IL-6) as a potential biomarker for detecting disease activity in Takayasu arteritis.

METHODS

A systematic review and meta-analysis was performed to assess differences in IL-6 levels in patients with active (aTA) and inactive Takayasu arteritis (iTA), as well as healthy controls (HCs), using validated activity scores. Study quality and the risk of bias were assessed using STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) and the Newcastle-Ottawa and Joanna Briggs checklist, respectively. For the meta-analysis, we pooled the raw mean IL-6 levels in each group and then estimated and pooled the crude mean differences between the groups. We applied a random-effects model in all analyses.

RESULTS

Of the 93 eligible articles, 10 were included after removing duplicates and studies that met the exclusion criteria. Overall, 1825 patients with a mean age ranging from 24 to 40.6 years were included. The pooled levels of IL-6 increased depending on disease activity as follows: HCs: 3.08 (95% confidence interval [CI], 0.88-5.28), iTA: 7.21 (3.61-10.82), and aTA: 22.67 (12.44-32.91) pg/mL. Patients with aTA had higher IL-6 levels than HCs (21.52 [95% CI, -0.43 to 43.47]) and those with iTA (16.69 [95% CI, 5.32-28.06]), whereas IL-6 levels were not different between HCs and patients with iTA (3.62 [95% CI, -13.18 to 20.42]).

CONCLUSIONS

Interleukin 6 levels are significantly increased in patients with aTA compared with those with iTA and HCs but not in patients with iTA compared with HCs. More studies are needed to establish the IL-6 cutoff value for assessing disease activity.

The Contribution of Innate Immunity in Large-Vessel Vasculitis: Detangling New Pathomechanisms beyond the Onset of Vascular Inflammation

Large-vessel vasculitis (LVV) are autoimmune and autoinflammatory diseases focused on vascular inflammation. The central core of the intricate immunological and molecular network resides in the disruption of the "privileged immune state" of the arterial wall. The outbreak, initially primed by dendritic cells (DC), is then continuously powered in a feed-forward loop by the intimate cooperation between innate and adaptive immunity. If the role of adaptive immunity has been largely elucidated, knowledge of the critical function of innate immunity in LVV is still fragile. A growing body of evidence has strengthened the active role of innate immunity players and their key signaling pathways in orchestrating the complex pathomechanisms underlying LVV. Besides DC, macrophages are crucial culprits in LVV development and participate across all phases of vascular inflammation, culminating in vessel wall remodeling. In recent years, the variety of potential pathogenic actors has expanded to include neutrophils, mast cells, and soluble mediators, including the complement system. Interestingly, new insights have recently linked the inflammasome to vascular inflammation, paving the way for its potential pathogenic role in LVV. Overall, these observations encourage a new conceptual approach that includes a more in-depth study of innate immunity pathways in LVV to guide future targeted therapies.

Platelet count as a potential predictor in refractory Takayasu arteritis

Platelet parameters have been recognized as important markers for disease severity in various types of diseases. The aim of our study was to investigate whether platelet count could be used as a potential predictor of refractory Takayasu arteritis (TAK). In this retrospective study, fifty-seven patients were selected as development data group to identify the associated risk factors and potential predictors of refractory TAK. Ninety-two TAK patients were included in the validation data group to verify the predictive value of platelet count for refractory TAK. Refractory TAK patients had higher levels of platelet (PLT) than non-refractory TAK patients (305.5 vs. 272.0 × 109/L, P = 0.043). For PLT, the best cut-off value was 296.5 × 109/L to predict refractory TAK. Elevated PLT (> 296.5 × 109/L) was found to be statistically related to refractory TAK (OR [95%CI] 4.000 [1.233-12.974], p = 0.021). In the validation data group, the proportion of refractory TAK in patients with elevated PLT was significantly higher than that in patients with non-elevated PLT (55.6% vs. 32.2%, P = 0.037). The 1-, 3- and 5-year cumulative incidence of refractory TAK were 37.0%, 44.4% and 55.6% in patients with elevated PLT, respectively. Elevated PLT (p = 0.035, hazard ratio (HR) 2.106) was identified as a potential predictor of refractory TAK. Clinicians should pay close attention to platelet levels in patients with TAK. For TAK patients with PLT greater than 296.5 × 109/L, closer monitoring of the disease and comprehensive assessment of disease activity are recommended to be alert to the occurrence of refractory TAK.

Exploration of molecular signatures associated with different clinical features of Takayasu arteritis based on a prospective cohort study

Takayasu arteritis (TAK) is complicated disorder without reliable biomarkers. Here, we aimed to explore TAK-associated factor panels and their changes after biologic treatment. Five factor panels were identified: 1. systemic inflammation: C3, ESR, CRP, PLT, IL-6, C4, and IgG; 2. vascular inflammation: YKL40, IL-16, PTX3, and CCL2; 3. immune regulation panel: IL-10, IFN-γ, CCL5, and MMP1; 4. angiogenesis and fibrosis: FGF, PDGFAB, and VEGF; and 5. vascular remodeling: CD19+ B cell ratio, MMP3, and leptin. Panel 1 parameters were closely related to disease activity, while Panel 5 parameters, particularly CD19+ B cell ratio and leptin, were significantly higher in ischemic patients. After treatment, tocilizumab had a stronger inhibitory effect on Panel 1 parameters, PTX3, and YKL-40, while adalimumab led to an increase in IL-16, CCL2, and leptin levels. Altogether, these data expanded our knowledge regarding molecular background in TAK development and shed light on precise treatment in future studies.

High level of serum complement 3 is a risk factor for vascular stenosis progression in TA patients receiving tocilizumab: a prospective observational study

BACKGROUND

The IL-6R antibody tocilizumab has been proven effective in treating Takayasu arteritis (TA). However, some patients show silent vascular stenosis progression (VSP) despite treatment with tocilizumab. The aim of the study was to explore the related risk factors of VSP in patients treated with tocilizumab.

METHODS

Patients receiving tocilizumab were enrolled from the prospective living ongoing East China Takayasu Arteritis cohort. Their medical information was uniformly recorded with a homogenized evaluation method. Magnetic resonant angiography or computed tomographic angiography was employed to monitor VSP during the follow-up period, and Cox regression analysis was performed to explore the related risk factors.

RESULTS

Thirty-eight patients were enrolled, among whom 18 (47.4%) experienced VSP, and seven and three patients experienced new and worsened vascular ischemic symptoms and events (VISE) during follow-up, respectively. The median period for VSP occurrence was 6.9 months during follow-up. Patients with VSP showed higher levels of baseline complement 3 (C3) than those in the patients without VSP. Multivariate Cox regression analysis revealed baseline C3 level (hazard ratio [HR] = 7.05, 95% confidence interval: 1.50-33.07, p = 0.013) was independently associated with VSP, with a cut-off value of 1.22 g/L.

CONCLUSIONS

47.4% of TA patients treated with tocilizumab would suffer VSP. A high C3 level is a risk factor for VSP in TA patients receiving tocilizumab, which may facilitate the option of tocilizumab in the future.

Medium-vessel and large-vessel vasculitis in children

PURPOSE OF REVIEW

This article serves as an up-to-date examination of the latest findings in the field of paediatric large-vessel and medium-vessel vasculitis.

RECENT FINDINGS

Over the last 2 years and in the wake of SARS-CoV2 pandemic, a multitude of studies have increased our insight into these conditions. Although large-vessel and medium-vessel vasculitis are uncommon amongst children, they are a complex and multisystem with a constantly evolving landscape. Increasing numbers of reports from low-income and middle-income countries are shaping our understanding of the epidemiology of vasculitis in children. The influence of infectious disease and the microbiome are of particular interest in unravelling pathogenetic aspects. Improved understanding of the genetics and immunology offer opportunities for better diagnostic options and biomarkers of disease as well as targeted therapies.

SUMMARY

In this review, we address recent findings in epidemiology, pathophysiology, clinical findings, bio-markers, imaging and treatment that have the potential to offer better management solutions for these uncommon conditions.

Biomarkers in the era of targeted therapy in giant cell arteritis and polymyalgia rheumatica: is it possible to replace acute-phase reactants?

Research into giant cell arteritis (GCA) and polymyalgia rheumatica (PMR) has become more important in the last few decades. Physicians are facing several challenges in managing the diagnosis, treatment, and relapses of GCA and PMR patients. The search for biomarkers could provide elements to guide a physician's decision. In this review, we aim to summarize the scientific publications about biomarkers in GCA and PMR in the past decade. The first point raised by this review is the number of clinical situations in which biomarkers could be useful: differential diagnosis of either GCA or PMR, diagnosis of underlying vasculitis in PMR, prediction of relapse or complications, disease activity monitoring, choice, and modification of treatments. The second point raised by this review is the large number of biomarkers studied, from common markers like C-reactive protein, erythrocyte sedimentation rate, or elements of blood count to inflammatory cytokines, growth factors, or immune cell subpopulations. Finally, this review underlines the heterogeneity between the studies and proposes points to consider in studies evaluating biomarkers in general and particularly in the case of GCA and PMR.

Elevated serum immunoglobulin level predicts high risk of 1-year recurrence in patients with Takayasu arteritis

BACKGROUND

The mechanism of humoral immunity to Takayasu arteritis (TAK) is not clear. In our study, we aimed to investigate the correlation between immunoglobulins and disease activity and the relationship between immunoglobulins and the prognosis of TAK patients.

METHODS

One hundred ninety TAK patients divided into two groups according to whether they had elevated immunoglobulins or not. We compared the demographic data and the clinical data between the two groups. Pearson correlation was used to analyze the relationship between immunoglobulin and disease activity, as well as the relationship between their changes. Immunohistochemical staining was used to compare the expression of humoral immune cells in TAK and atherosclerotic patients. One hundred twenty TAK patients who achieved remission within 3 months after discharge were followed up for 1 year. Logistic regression was used to explore the relationship between elevated immunoglobulins and recurrence.

RESULTS

Disease activity and inflammatory factors were significantly higher in the group with elevated immunoglobulins than in the normal group [NIH (3.0 vs. 2.0, P = 0.001), ITAS-A (9.0 vs. 7.0, P = 0.006)]. Compared with atherosclerotic patients, CD138 + plasma cells were significantly increased in the aortic wall of patients with TAK (P = 0.021). Changes in IgG correlated well with CRP and ESR [CRP (r = 0.40, P = 0.027), ESR (r = 0.64, P < 0.001)]. For patients with TAK in remission, elevated immunoglobulins was associated with 1-year recurrence [OR95%, CI: 2.37 (1.03, 5.47), P = 0.042].

CONCLUSIONS

Immunoglobulins is of clinical value in evaluating disease activity in TAK patients. Moreover, the dynamic changes of IgG were correlated with the changes in inflammatory indicators in TAK patients.

Serum C3 complement levels predict prognosis and monitor disease activity in Guillain-Barré syndrome

OBJECTIVE

Biomarkers are needed to predict prognosis and disease activity in patients with Guillain-Barré syndrome (GBS). The complement system is a key player in the pathogenesis of GBS. This study aimed to assess the potential utility of serum complement proteins as novel biomarkers in GBS.

METHODS

We reviewed the medical records of 76 GBS patients with C3 and C4 measurements during hospitalization between 2010 and 2021. Clinical outcomes were correlated with baseline serum C3, C4, and seven additional predictors: four existing biomarkers (GM1, albumin, immunoglobulin G, neutrophil-lymphocyte ratio) and three clinical factors from the modified Erasmus GBS outcome score model. Five complement activation products (C3a, C4a, C5a, soluble C5b-9, factor Bb) were measured in 35 patients and were compared with C3 and C4 levels. Longitudinal changes in C3 and C4 levels were compared with the disease course in 12 patients.

RESULTS

Higher C3, but not C4, was associated with poorer outcomes: lower Medical Research Council sum scores (MRCSS), higher GBS disability score (GBSDS), longer hospitalization, and more frequent treatment-related fluctuations. Age, MRCSS at admission, and baseline serum C3 were significant independent indicators of 1- and 3-month GBSDS. We found that C3 was positively correlated with C3a (r = 0.32) and C5a (r = 0.37), which indicates an activated complement cascade with high C3. Longitudinal change of C3 coincided with clinical severity of the disease course.

INTERPRETATION

This study highlights the use of serum C3 as a novel mechanistic biomarker in GBS. Larger prospective studies are needed to validate our findings.

Biomarkers in Takayasu arteritis

Takayasu arteritis (TA) is a rare large vasculitis with unknown etiology, which affects the aorta and its primary branches, as well as the pulmonary and coronary arteries. Cellular and humoral immunity, chronic inflammation, and genetic factors are involved into TA pathogenesis. Several biomarkers, such as MMPs, TIMPs, cytokines, cell adhesion molecules, autoantibodies, complements, PTX3, sRAGE, NT-proBNP, 8-isoPGF_2α, NO₂^-, acute-phase and immunology-related proteins, thrombogenicity markers, ghrelin leptin and adipokines, endothelial damage and repair factors, genetic markers etc., related to the pathogenesis could be observed in patients with TA. These biomarkers have revealed great values in early diagnosis, evaluating disease activity, guiding clinical treatment options, and thus demonstrated significant clinical application values in TA. The combination of biomarkers assay and imaging examination may detect TA more accurately. The aim of this review is to systemically observe the clinical significance of these biomarkers in TA.

Outcome Measures and Biomarkers for Disease Assessment in Takayasu Arteritis

Takayasu arteritis (TAK) is a less common large vessel vasculitis where histopathology of involved arteries is difficult to access except during open surgical procedures. Assessment of disease activity in TAK, therefore, relies on surrogate measures. Clinical disease activity measures such as the National Institutes of Health (NIH) score, the Disease Extent Index in TAK (DEI.TAK) and the Indian TAK Clinical Activity Score (ITAS2010) inconsistently associate with acute phase reactants (APRs). Computerized tomographic angiography (CTA), magnetic resonance angiography (MRA), or color Doppler Ultrasound (CDUS) enables anatomical characterization of stenosis, dilatation, and vessel wall characteristics. Vascular wall uptake of 18-fluorodeoxyglucose or other ligands using positron emission tomography computerized tomography (PET-CT) helps assess metabolic activity, which reflects disease activity well in a subset of TAK with normal APRs. Angiographic scoring systems to quantitate the extent of vascular involvement in TAK have been developed recently. Erythrocyte sedimentation rate and C-reactive protein have a moderate performance in distinguishing active TAK. Numerous novel biomarkers are under evaluation in TAK. Limited literature suggests a better assessment of active disease by combining APRs, PET-CT, and circulating biomarkers. Validated damage indices and patient-reported outcome measures specific to TAK are lacking. Few biomarkers have been evaluated to reflect vascular damage in TAK and constitute important research agenda.

Utility of serum complement factors C3 and C4 as biomarkers during therapeutic management of giant cell arteritis

OBJECTIVE

There is a strong unmet need for biomarkers in giant cell arteritis (GCA), as C-reactive protein (CRP) may be unreliable in patients treated with Tocilizumab (TCZ). We aimed to assess whether C3 and C4 are useful biomarkers in GCA patients, particularly in those treated with TCZ.

METHOD

We retrospectively enrolled all patients who underwent C3 and C4 measurement at baseline. All patients were evaluated at 3, 6, 12, and 24 months after diagnosis, as part of routine follow-up. Two assessments after the end of the observational period, in case of further relapses, were also included.

RESULTS

At baseline, mean ± sd levels (mg/dL) of C3 (133 ± 28.99) and C4 (25.9 ± 9.04) were within normal ranges. During follow-up, C3 and C4 decreased in patients attaining remission (107.07 ± 19.86, p = 0.0006; 19.86 ± 10.27, p = 0.01, respectively) and sustained remission (95.85 ± 18.04, p = 0.001; 15.61 ± 9.75, p = 0.006). In TCZ-treated patients, even stronger decreases in C3 (83.11 ± 19.66, p = 0.001) and C4 (8.26 ± 3.83, p < 0.0001) were observed, and their values were not correlated with CRP or erythrocyte sedimentation rate.

CONCLUSION

C3 and C4 do not seem useful in the diagnosis of GCA, as normal values do not rule out active vasculitis. However, C3 and C4 correlate with disease activity. As the low C4 levels found in TCZ-treated patients are not correlated with CRP, C4 should be evaluated as a potential biomarker of disease activity and treatment response.

Using the co-expression network of T cell-activation-related genes to assess the disease activity in Takayasu's arteritis patients

Background

There have been lacking reliable serum biomarkers in assessing the disease activity of Takayasu’s arteritis (TAK). This study aimed to assess the disease activity of TAK by assayed gene expression levels in peripheral mononuclear cells (PBMCs).

Methods

The expression level of genes that essential in T cell activation in PBMCs in active TAK patients, inactive TAK patients, and healthy controls were detected by real-time fluorescence quantitative polymerase chain reaction, including TCR, CD28, CD40, CD40L, PD-1, PD-L1, PD-L2, CTLA4, TIGIT, TIM3, LAG3, CCL5, T-bet, RORC, and FOXP3. Gene co-expression network was established, and the signature of the topology structure in active TAK patients compared to the inactive TAK patients were extracted and described by formulas. Respectively, the disease activity was assessed by the routine serum biomarkers, including ESR, CRP, IL-6, and TNF-α, the gene expression level of TCR, CD28, T-bet, and RORC, as well as the signature of the topology structure, and the diagnostic efficacies were compared.

Results

Compared with the inactive TAK patient group, the active TAK patient group had a greater clustering coefficient in the network consisting of genes that essential in T cell activation. When assessing the disease activity used this signature of topology structure, the sensitivity was 90.9%, the specificity was 100%, and the AUC was 0.98, which was greater than the AUCs of these biomarkers.

Conclusions

The signature of the topology structure could distinguish the active TAK patients from inactive TAK patients. This maybe is a novel evaluation algorithm of disease activity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02636-2.