Different Features of Interleukin-37 and Interleukin-18 as Disase Activity Markers of Adult-Onset Still's Disease

Recent advances and evolving concepts in Still's disease

Still's disease is a rare inflammatory syndrome that encompasses systemic juvenile idiopathic arthritis and adult-onset Still's disease, both of which can exhibit life-threatening complications, including macrophage activation syndrome (MAS), a secondary form of haemophagocytic lymphohistiocytosis. Genetic insights into Still's disease involve both HLA and non-HLA susceptibility genes, suggesting the involvement of adaptive immune cell-mediated immunity. At the same time, phenotypic evidence indicates the involvement of autoinflammatory processes. Evidence also implicates the type I interferon signature, mechanistic target of rapamycin complex 1 signalling and ferritin in the pathogenesis of Still's disease and MAS. Pathological entities associated with Still's disease include lung disease that could be associated with biologic DMARDs and with the occurrence of MAS. Historically, monophasic, recurrent and persistent Still's disease courses were recognized. Newer proposals of alternative Still's disease clusters could enable better dissection of clinical heterogeneity on the basis of immune cell profiles that could represent diverse endotypes or phases of disease activity. Therapeutically, data on IL-1 and IL-6 antagonism and Janus kinase inhibition suggest the importance of early administration in Still's disease. Furthermore, there is evidence that patients who develop MAS can be treated with IFNγ antagonism. Despite these developments, unmet needs remain that can form the basis for the design of future studies leading to improvement of disease management.

Interleukin-18 as a severity marker and novel potential therapeutic target for epidermolytic ichthyosis

BACKGROUND

Epidermolytic ichthyosis (EI) is a major form of nonsyndromic inherited ichthyosis, characterized by erythroderma, marked hyperkeratosis and scale, bulla and erosion at birth, associated with KRT1/KRT10 mutations. The cytokine and chemokine profiles in EI are poorly understood, and specific treatment options have not been established.

AIM

To explore novel biomarkers and therapeutic targets in patients with EI.

METHODS

We analysed cytokine levels in serum and skin samples from 10 patients with inherited ichthyosis, including seven patients with EI. Wild-type and mutant KRT1 constructs were established and transfected into HaCaT cells, an immortalized keratinocyte cell line, for in vitro immunoblotting and immunocytochemistry analyses.

RESULTS

Multiplex cytokine/chemokine analysis revealed that 10 cytokines/chemokines [interleukin (IL)-1β, IL-4, IL-17A, IL-16, IL-18, IL-1 receptor-α, macrophage colony-stimulating factor, interferon-α2, basic fibroblast growth factor and monocyte chemotactic protein-3] were significantly increased in patients with EI. Furthermore, IL-18 levels were significantly higher in patients with EI [n = 7; 2714.1 (1438.0) pg mL-1] than in healthy controls [n = 11; 218.4 (28.4) pg mL-1, P < 0.01]. Immunohistochemical analyses showed that IL-18 expression was elevated in skin samples from patients with EI. Serum IL-18 levels correlated with the severity of ichthyosis, as measured by the Ichthyosis Scoring System. Immunoblotting analysis revealed that mature IL-18 levels were increased in the supernatant of mutant KRT1 expressing HaCaT cells. Additionally, these cells showed NLRP3 aggregation in the cytoplasm and ASC clustered around mutant keratin aggregations. These findings suggest that mutant keratin might promote the activation of the NLRP3 inflammasome and its downstream caspase-1-mediated IL-18 release in keratinocytes from patients with EI.

CONCLUSIONS

Our results suggest that serum IL-18 is a severity marker released from the skin of patients with EI. Blockade of IL-18 may be a useful novel therapeutic option for patients with EI.

Performance of the modified Systemic Manifestation Score for systemic juvenile idiopathic arthritis in Adult-onset Still's disease

OBJECTIVES

To compare the ability of the modified Systemic Manifestation Score (mSMS) and the mPouchot score to distinguish adult-onset Still's disease (AOSD) with high disease severity in a large cohort.

METHODS

We scored the disease severity of 174 patients and categorized them into high and low disease severity states. The correlation of mSMS and mPouchot score with ESR, CRP, ferritin, liver function tests, and serum cytokines was investigated. Receiver operator characteristic (ROC) curve and logistic regression analysis were performed to compare the ability of mSMS and mPouchot to distinguish patients with severe AOSD.

RESULTS

Both mSMS and mPouchot score were positively correlated with ESR (both P < 0.001), CRP (both P < 0.0001), and serum ferritin (both P < 0.0001). Moreover, both mSMS and mPouchot score are significantly associated with liver dysfunction and high IL-18 (both P < 0.0001) and IL-6 (both P < 0.01) levels in AOSD patients. Furthermore, the area under curve (AUC) value of mSMS was significantly less than of mPouchot score (0.71 for mSMS, 0.81 for mPouchot score, P < 0.0001). Compared with mPouchot score, mSMS had higher sensitivity (75.64% vs 74.36%) and lower specificity (55.06% vs 76.40%). And mSMS had a worse performance in assessing high disease severity than mPouchot score in logistic analysis.

CONCLUSION

Both scores are proven as effective to assess disease severity of AOSD. By contrast, mSMS perform worse in assessing high disease severity of AOSD patients than mPouchot score. Key Points • Both modified Systemic Manifestation Score (mSMS) and modified Pouchot score (mPouchot score) positively correlated with ESR, CRP, and serum ferritin of AOSD patients. • Both scores are significantly associated with impaired liver function and high serum cytokine levels. • mSMS had lower discriminative ability than mPouchot score to distinguish high disease severity of AOSD patients.

Mast Cell Cytokines in Acute and Chronic Gingival Tissue Inflammation: Role of IL-33 and IL-37

Much evidence suggests autoimmunity in the etiopathogenesis of periodontal disease. In fact, in periodontitis, there is antibody production against collagen, DNA, and IgG, as well as increased IgA expression, T cell dysfunction, high expression of class II MHC molecules on the surface of gingival epithelial cells in inflamed tissues, activation of NK cells, and the generation of antibodies against the azurophil granules of polymorphonuclear leukocytes. In general, direct activation of autoreactive immune cells and production of TNF can activate neutrophils to release pro-inflammatory enzymes with tissue damage in the gingiva. Gingival inflammation and, in the most serious cases, periodontitis, are mainly due to the dysbiosis of the commensal oral microbiota that triggers the immune system. This inflammatory pathological state can affect the periodontal ligament, bone, and the entire gingival tissue. Oral tolerance can be abrogated by some cytokines produced by epithelial cells and activated immune cells, including mast cells (MCs). Periodontal cells and inflammatory-immune cells, including mast cells (MCs), produce cytokines and chemokines, mediating local inflammation of the gingival, along with destruction of the periodontal ligament and alveolar bone. Immune-cell activation and recruitment can be induced by inflammatory cytokines, such as IL-1, TNF, IL-33, and bacterial products, including lipopolysaccharide (LPS). IL-1 and IL-33 are pleiotropic cytokines from members of the IL-1 family, which mediate inflammation of MCs and contribute to many key features of periodontitis and other inflammatory disorders. IL-33 activates several immune cells, including lymphocytes, Th2 cells, and MCs in both innate and acquired immunological diseases. The classic therapies for periodontitis include non-surgical periodontal treatment, surgery, antibiotics, anti-inflammatory drugs, and surgery, which have been only partially effective. Recently, a natural cytokine, IL-37, a member of the IL-1 family and a suppressor of IL-1b, has received considerable attention for the treatment of inflammatory diseases. In this article, we report that IL-37 may be an important and effective therapeutic cytokine that may inhibit periodontal inflammation. The purpose of this paper is to study the relationship between MCs, IL-1, IL-33, and IL-37 inhibition in acute and chronic inflamed gingival tissue.

Interleukin-18: a biomarker with therapeutic potential in adult-onset Still's disease

INTRODUCTION

Adult-onset Still's disease (AOSD) is an autoinflammatory disease driven by the innate immune response. Given the ambiguity in clinical presentation and lack of specific diagnostic biomarkers, AOSD diagnosis is usually delayed in the early stage. Because AOSD is a rare disease with clinical heterogeneity, there is no consensus on its treatment currently. This review summarizes the current research evidence regarding the pathogenic role and the diagnostic or therapeutic potential of interleukin (IL)-18 in AOSD.

AREAS COVERED

We searched the MEDLINE database using the PubMed interface and reviewed English-language literature from 1971 to 2022. This review focusing on IL-18 discusses its pathogenic role and clinical implications in AOSD.

EXPERT OPINION

NLRP3-inflammasome activation with IL-18 overproduction plays a pathogenic role in AOSD. IL-18 is closely linked to the clinical manifestations and disease activity of AOSD and may be a diagnostic biomarker. Given its pathogenic role in AOSD, IL-18 could become a potential therapeutic target. IL-18 binding protein (IL-18BP) negatively regulates the biological activity of IL-18 by inhibiting IL-18 signaling, and a clinical trial revealed that IL-18BP (Tadekinig alfa) treatment was well-tolerated and effective for AOSD. Recently, monoclonal antibodies against IL-18 have been under evaluation in a phase 1b trial.

Strategy and Challenges of Paraclinical Examinations in Adult-Onset Still’s Disease

Adult-onset Still’s disease is a complex autoinflammatory disease with a multifactorial etiology. Its presentation is less stereotypical than that of a monogenic autoinflammatory disease and is actually relatively common with few specific signs. To avoid under- or over-prescription of complementary examinations, it is useful to advance in a structured manner, taking into consideration the actual added value of each supplemental examination. In this review, we detail the different complementary tests used in adult Still’s disease. We consider them from three different angles: positive diagnostic approach, the differential diagnosis, and the screening for complications of the disease. After discussing the various tests at our disposal, we look at the classical diagnostic strategy in order to propose a structured algorithm that can be used in clinical practice. We conclude with the prospects of new complementary examinations, which could in the future modify the management of patients.

Therapeutic potential of targeting IL-1 family cytokines in chronic inflammatory skin diseases

The interleukin-1 (IL-1) family of cytokines is a central regulator of a myriad of immunological responses. It comprises several cytokines, including those belonging to the IL-1, IL-36 and IL-18 subfamilies, as well as IL-33. The IL-1 family primarily plays a role in orchestrating innate immune responses but also in adaptive immunity. Increased interest in the IL-1 family occurred following the discovery that dysregulation of IL-1 signalling underlies the pathogenesis of several monogenic auto-inflammatory diseases, characterized by sterile inflammation involving the skin and other organs. This also provided increased understanding of the role of innate immunity and the IL-1 family in polygenic auto-inflammatory skin conditions, such as neutrophilic dermatoses, as well as in some of the most common chronic inflammatory skin diseases, such as psoriasis or hidradenitis suppurativa. Several therapeutic agents have been developed to inhibit the IL-1 family members and their signalling pathways. These have shown therapeutic efficacy in several chronic inflammatory skin disorders. The aim of this review is to thoroughly describe the consequences of pathological dysregulation of IL-1, IL-33, IL-36, IL-18 pathways in dermatological conditions and to provide a forward-looking update on therapeutic strategies targeting signalling by IL-1 family cytokines.

Usefulness of Interleukin-18 as a Diagnostic Biomarker to Differentiate Adult-Onset Still's Disease With/Without Macrophage Activation Syndrome From Other Secondary Hemophagocytic Lymphohistiocytosis in Adults

Background

Interleukin (IL)-18 is markedly elevated in systemic inflammatory diseases that cause the ‘cytokine storm’ such as adult-onset Still’s disease (AOSD) and hemophagocytic lymphohistiocytosis (HLH). The differences in IL-18 between AOSD and HLH, especially in adults, is uncertain. Macrophage activation syndrome (MAS), a form of secondary HLH, is often difficult to differentiate cases of AOSD that include MAS from other secondary HLH. In this case-control study, we investigated whether serum IL-18 levels could be a useful biomarker for the differential diagnosis of AOSD with or without MAS (AOSD group) and other secondary HLH in adults (adult HLH group).

Patients and Methods

We enrolled 46 patients diagnosed with AOSD including 9 patients with MAS and 31 patients in the adult HLH group, which excluded AOSD-associated MAS. The clinical features and laboratory data were compared between the AOSD and adult HLH groups. In addition, we subdivided the AOSD group (with or without MAS) and the adult HLH group (whether lymphoma-associated or not) and compared the four groups. A logistic regression analysis was used to identify factors with high efficacy in differentiating the two groups, followed by a receiver operating characteristic (ROC) curve analysis to evaluate the differential diagnostic ability of IL-18. We analyzed the correlation between IL-18 and various laboratory parameters in the AOSD group.

Results

Serum IL-18 levels of patients in the AOSD groups were significantly higher than those of the adult HLH groups, and were closely correlated with ferritin, soluble interleukin-2 receptor (sIL-2R), and other laboratory data. Univariate and multivariate logistic regression analyses revealed that IL-18, sIL-2R, and ‘arthralgia or arthritis’ are independent factors useful in the differential diagnosis of AOSD from adult HLH. In the differential diagnosis of both groups, the area under the curve obtained from the ROC curve of IL-18 with a cutoff value of 18,550 pg/mL was 0.91 (95% confidence interval 0.83–1.00; sensitivity 90.3%, specificity 93.5%), and the differential diagnosis ability of IL-18 was superior to that of other laboratory data.

Conclusions

IL-18 could be a useful biomarker for the differential diagnosis of AOSD and adult HLH.

Adult-onset Still's disease or systemic-onset juvenile idiopathic arthritis and spondyloarthritis: overlapping syndrome or phenotype shift?

OBJECTIVES

Systemic-onset juvenile idiopathic arthritis (SJIA) and adult-onset Still's disease (AOSD) are the same sporadic systemic auto-inflammatory disease. Spondyloarthritis (SpA) is a group of inflammatory non-autoimmune disorders. We report the observations of eight patients with SJIA/AOSD who also presented features of SpA during their disease evolution and estimate the prevalence of SpA in SJIA/AOSD.

METHODS

This was a retrospective national survey of the departments of paediatric and adult rheumatology and internal medicine. To be included, SJIA patients had to fulfil the ILAR criteria, AOSD patients the Yamaguchi or Fautrel criteria, and all patients the ASAS classification criteria for axial or peripheral SpA, ESSG criteria for spondyloarthropathy or CASPAR criteria for psoriatic arthritis. The data were collected with a standardized form.

RESULTS

Eight patients (five adults) were identified in one paediatric and two adult departments. In all but one patient, SpA manifestations occurred several years after SJIA/AOSD onset (mean delay 6.2 ± 3.8 years). Two patients had peripheral and three axial SpA, and four later exhibited psoriatic arthritis and one SAPHO syndrome. The prevalence of SpA in an adult cohort of 76 patients with AOSD was 6.58% (95% CI [2.17-14.69]), greater than the prevalence of SpA in the French general population (0.3%, 95%CI [0.17-0.46]). The prevalence of SpA in an SJIA cohort of 30 patients was 10% (95%CI [2.11-26.53]), more than that reported in the general population of industrialized countries, estimated at 0.016% to 0.15%.

CONCLUSION

Whilst the temporal disassociation between SpA and AOSD in most cases might suggest a coincidental finding, our work raises the possibility of an SpA AOSD spectrum overlap that needs further study.

The effectiveness of tocilizumab in treating refractory adult-onset Still's disease with dichotomous phenotypes: IL-18 is a potential predictor of therapeutic response

OBJECTIVE

Adult-onset Still's disease (AOSD) is a systemic inflammatory disorder with clinical heterogeneity. Although tocilizumab (TCZ), an interleukin (IL)-6 receptor inhibitor, is an effective treatment for AOSD, the evidence regarding its efficacy on systemic or articular subtypes is conflicting. Furthermore, the predictors of therapeutic response are still elusive and worthy of exploration.

METHODS

This two-center retrospective study analyzed the effectiveness and safety profile of TCZ treatment in 28 patients with refractory AOSD. The 28-joint disease activity score (DAS28) and systemic activity score were assessed before and during TCZ treatment period at weeks 12, 24, 36, and 48. Plasma levels of proinflammatory cytokines at baseline were determined using ELISA method.

RESULTS

Among the systemic subtype patients, 10 (58.8%), 13 (76.5%), 14 (82.4%), and 15 (88.2%) patients achieved complete remission at week 12, 24, 36, and 48, respectively, in comparison to 2 (22.2%), 5 (55.6%), 6 (66.7%), and 7 (77.8%) who achieved disease remission (DAS28 < 2.6) at weeks 12, 24, 36, and 48, respectively, among articular subtype patients. The systemic activity scores and inflammatory parameters were significantly decreased after 12-week TCZ therapy, and TCZ could significantly reduce corticosteroid dose in AOSD patients. Multivariate analysis reveals that baseline IL-18 level is a significant predictor of poor therapeutic response at week 24 (odds ratio 7.86, p < 0.05).

CONCLUSION

AOSD patients refractory to high-dose corticosteroids and methotrexate may respond well to TCZ treatment with a steroid-sparing effect and an acceptable safety. A high baseline IL-18 level may be a predictor of poor therapeutic response. Key Points • Tocilizumab may be effective and well-tolerated in refractory AOSD patients regardless of disease subtypes. • High plasma levels of IL-18 may predict poor response to tocilizumab in AOSD patients.

Circulating Interleukin-37 Levels in Healthy Adult Humans - Establishing a Reference Range

Interleukin (IL)-37 has an important function in limiting excessive inflammation. Its expression is increased in numerous inflammatory and autoimmune conditions and correlates with disease activity, suggesting it could have potential as a disease biomarker. Nevertheless, a reference range has yet to be determined. Our aim was to establish the first reference range of circulating IL-37 levels in healthy adult humans. PubMed was searched for studies reporting blood IL-37 concentrations in healthy adult subjects as measured by enzyme-linked immunosorbent assay. Nineteen studies were included in the analysis. Mean IL-37 levels were weighted by sample sizes, and weighted mean lower and upper levels ( ± 2SD of means) were calculated to provide a weighted mean and reference range. IL-37 levels were quantified in either serum or plasma from a total of 1035 (647 serum; 388 plasma) healthy subjects. The serum, plasma and combined matrix weighted means (reference ranges) were 72.9 (41.5 – 104.4) pg/mL, 83.9 (41.1 – 126.8) pg/mL, and 77.1 (41.4 – 112.8) pg/mL, respectively. There were no significant differences between serum and plasma means and upper and lower limits. Study means and upper IL-37 levels were significantly higher in Chinese population studies. From our analysis, a preliminary reference range for circulating IL-37 levels in healthy human adults has been established. In order to determine a reliable reference range for clinical application, large, prospective, multi-ethnic, healthy population studies are necessary. In addition, demographics, sample matrix, collection, processing and storage methods potentially affecting IL-37 detection levels should be thoroughly investigated.