Th17 cell responses in spondyloarthritis

The Role of H3K27me3-Mediated Th17 Differentiation in Ankylosing Spondylitis

Ankylosing spondylitis (AS) is a common chronic progressive inflammatory autoimmune disease. T helper 17 (Th17) cells are the major effector cells mediating AS inflammation. Histone 3 Lys 27 trimethylation (H3K27me3) is an inhibitory histone modification that silences gene transcription and plays an important role in Th17 differentiation. The objective of this study was to investigate the expression of H3K27me3 in patients with AS and to explore its epigenetic regulation mechanism of Th17 differentiation during AS inflammation. We collected serum samples from 45 patients with AS at various stages and 10 healthy controls to measure their Interleukin-17 (IL-17) levels using ELISA. A quantitative polymerase chain reaction was used to quantify the mRNA levels of RORc and the signaling molecules of the JAK2/STAT3 pathway, JMJD3, and EZH2. Additionally, Western blot analysis was performed to quantify the protein levels of H3K27me3, RORγt, JAK2, STAT3, JMJD3, and EZH2 in cell protein extracts. The results showed that H3K27me3 expression in peripheral blood mononuclear cells (PBMCs) was significantly lower in patients with active AS compared to both the normal control groups and those with stable AS. Moreover, a significant negative correlation was observed between H3K27me3 expression and the characteristic transcription factor of Th17 differentiation, RORγt. We also discovered that patients with active AS exhibited significantly higher levels of JMJD3, an inhibitor of H3K27 demethylase, compared to the normal control group and patients with stable AS, while the expression of H3K27 methyltransferase (EZH2) was significantly lower. These findings suggest that H3K27me3 may be a dynamic and important epigenetic modification in AS inflammation, and JMJD3/EZH2 regulates the methylation level of H3K27me3, which may be one of the key regulatory factors in the pathogenesis of AS. These findings contribute to our understanding of the role of epigenetics in AS and may have implications for the development of novel therapeutic strategies for AS.

Microbiota-dependent indole production is required for the development of collagen-induced arthritis

Altered tryptophan catabolism has been identified in inflammatory diseases like rheumatoid arthritis (RA) and spondyloarthritis (SpA), but the causal mechanisms linking tryptophan metabolites to disease are unknown. Using the collagen-induced arthritis (CIA) model we identify alterations in tryptophan metabolism, and specifically indole, that correlate with disease. We demonstrate that both bacteria and dietary tryptophan are required for disease, and indole supplementation is sufficient to induce disease in their absence. When mice with CIA on a low-tryptophan diet were supplemented with indole, we observed significant increases in serum IL-6, TNF, and IL-1β; splenic RORγt+CD4+ T cells and ex vivo collagen-stimulated IL-17 production; and a pattern of anti-collagen antibody isotype switching and glycosylation that corresponded with increased complement fixation. IL-23 neutralization reduced disease severity in indole-induced CIA. Finally, exposure of human colon lymphocytes to indole increased expression of genes involved in IL-17 signaling and plasma cell activation. Altogether, we propose a mechanism by which intestinal dysbiosis during inflammatory arthritis results in altered tryptophan catabolism, leading to indole stimulation of arthritis development. Blockade of indole generation may present a novel therapeutic pathway for RA and SpA.

The Expression of the Alpha7 Nicotinic Acetylcholine Receptor and the Effect of Smoking in Curdlan-Administered SKG Mice

Nicotine, an abundant molecule in tobacco, has immunomodulatory effects on inflammatory diseases, primarily due to the activation of alpha7 nicotinic acetylcholine receptor (α7 nAChR). We aim to evaluate the expression of the α7 nAChR+ cells in joint tissue and the effect of smoking on immune cells and peripheral arthritis in curdlan-administered SKG mice, a murine model of spondyloarthropathy (SpA). The SKG mice were injected with curdlan two times at 2-week intervals and were divided into two groups; one exposed to cigarette smoke and the other not exposed. We found that the α7 nAChR+ cells increased in the joint tissue of curdlan-administered SKG mice compared to in the wild type. Furthermore, the peripheral arthritis scores and histological scores for synovial inflammation were lower in smoke-exposed curdlan-administered SKG mice than in mice not exposed to smoke. Immunofluorescence staining of the α7 nAChR+ and IL-17A+ cells was lower in the synovia of smoke-exposed mice than the control mice. The proportions of α7 nAChR+IL-17A+ and α7 nAChR+IL-17A+FOXP3+ cells also decreased in the synovia of smoke-exposed mice compared with the controls. We observed an increase in the α7 nAChR+ cells within the joint tissue of curdlan-administered SKG mice and that cigarette smoke had an influence on both peripheral arthritis and immune cell population, especially α7 nAChR+ cells. Thus, exposure to cigarette smoke after arthritogenic stimuli may have an anti-arthritogenic effect in curdlan-administered SKG mice.

The chromatin and single-cell transcriptional landscapes of CD4 T cells in inflammatory bowel disease link risk loci with a proinflammatory Th17 cell population

Introduction

The imbalance between Th17 and regulatory T cells in inflammatory bowel diseases (IBD) promotes intestinal epithelial cell damage. In this scenario, T helper cell lineage commitment is accompanied by dynamic changes to the chromatin that facilitate or repress gene expression.

Methods

Here, we characterized the chromatin landscape and heterogeneity of intestinal and peripheral CD4 T cellsfrom IBD patients using in house ATAC-Seq and single cell RNA-Seq libraries.

Results

We show that chromatin accessibility profiles of CD4 T cells from inflamed intestinal biopsies relate to genes associated with a network of inflammatory processes. After integrating the chromatin profiles of tissue-derived CD4 T cells and in-vitro polarized CD4 T cell subpopulations, we found that the chromatin accessibility changes of CD4 T cells were associated with a higher predominance of pathogenic Th17 cells (pTh17 cells) in inflamed biopsies. In addition, IBD risk loci in CD4 T cells were colocalized with accessible chromatin changes near pTh17-related genes, as shown in intronic STAT3 and IL23R regions enriched in areas of active intestinal inflammation. Moreover, single cell RNA-Seq analysis revealed a population of pTh17 cells that co-expresses Th1 and cytotoxic transcriptional programs associated with IBD severity.

Discussion

Altogether, we show that cytotoxic pTh17 cells were specifically associated with IBD genetic variants and linked to intestinal inflammation of IBD patients.

Inhibition of NETosis via PAD4 alleviated inflammation in giant cell myocarditis

Giant cell myocarditis (GCM) is a rare, usually rapidly progressive, and potentially fatal disease. Detailed inflammatory responses remain unknown, in particular the formation of multinucleate giant cells. We performed single-cell RNA sequencing analysis on 15,714 Cd45+ cells extracted from the hearts of GCM rats and normal rats. NETosis has been found to contribute to the GCM process. An inhibitor of NETosis, GSK484, alleviated GCM inflammation in vivo. MPO (a marker of neutrophils) and H3cit (a marker of NETosis) were expressed at higher levels in patients with GCM than in patients with DCM and healthy controls. Imaging mass cytometry analysis revealed that immune cell types within multinucleate giant cells included CD4+ T cells, CD8+ T cells, neutrophils, and macrophages but not B cells. We elucidated the role of NETosis in GCM pathogenesis, which may serve as a potential therapeutic target in the clinic.

Immune cells and their related genes provide a new perspective on the common pathogenesis of ankylosing spondylitis and inflammatory bowel diseases

Background

The close relationship between ankylosing spondylitis (AS) and inflammatory bowel diseases (IBD) has been supported by many aspects, including but not limited to clinical manifestations, epidemiology and pathogenesis. Some evidence suggests that immune cells actively participated in the pathogenesis of both diseases. However, information on which cells are primarily involved in this process and how these cells mobilize, migrate and interact is still limited.

Methods

Datasets were downloaded from Gene Expression Omnibus (GEO) database. Common differentially expressed genes (coDEGs) were identified by package “limma”. The protein-protein interaction (PPI) network and Weighted Gene Co-Expression Network Analysis (WGCNA) were used to analyze the interactions between coDEGs. KEGG pathway enrichment analysis and inverse cumulative distribution function were applied to identify common differential pathways, while Gene Set Enrichment Analysis (GSEA) was used to confirm the significance. Correlation analysis between coDEGs and immune cells led to the identification of critical immune-cell-related coDEGs. The diagnostic models were established based on least absolute shrinkage and selection operator (LASSO) regression, while receiver operating characteristic (ROC) analysis was used to identify the ability of the model. Validation datasets were imported to demonstrate the significant association of coDEGs with specific immune cells and the capabilities of the diagnostic model.

Results

In total, 67 genes were up-regulated and 185 genes were down-regulated in both diseases. Four down-regulated pathways and four up-regulated pathways were considered important. Up-regulated coDEGs were firmly associated with neutrophils, while down-regulated genes were significantly associated with CD8+ T−cells and CD4+ T−cells in both AS and IBD datasets. Five up-regulated and six down-regulated key immue-cell-related coDEGs were identified. Diagnostic models based on key immue-cell-related coDEGs were established and tested. Validation datasets confirmed the significance of the correlation between coDEGs and specific immune cells.

Conclusion

This study provides fresh insights into the co-pathogenesis of AS and IBD. It is proposed that neutrophils and T cells may be actively involved in this process, however, in opposite ways. The immue-cell-related coDEGs, revealed in this study, may be relevant to their regulation, although relevant research is still lacking.

Cytokine competent gut-joint migratory T Cells contribute to inflammation in the joint

Although studies have identified the presence of gut-associated cells in the enthesis of joints affected by spondylarthritis (SpA), a direct link through cellular transit between the gut and joint has yet to be formally demonstrated. Using KikGR transgenic mice to label in situ and track cellular trafficking from the distal colon to the joint under inflammatory conditions of both the gut and joint, we demonstrate bona-fide gut-joint trafficking of T cells from the colon epithelium, also called intraepithelial lymphocytes (IELs), to distal sites including joint enthesis, the pathogenic site of SpA. Similar to patients with SpA, colon IELs from the TNF^ΔARE/+ mouse model of inflammatory bowel disease and SpA display heightened TNF production upon stimulation. Using ex vivo stimulation of photo-labeled gut-joint trafficked T cells from the popliteal lymph nodes of KikGR and KikGR TNF^ΔARE/+ we saw that the CD4+ photo-labeled population was highly enriched for IL-17 competence in healthy as well as arthritic mice, however in the TNF^ΔARE/+ mice these cells were additionally enriched for TNF. Using transfer of magnetically isolated IELs from TNF^+/+ and TNF^ΔARE/+ donors into Rag1 ^-/- hosts, we confirmed that IELs can exacerbate inflammatory processes in the joint. Finally, we blocked IEL recruitment to the colon epithelium using broad spectrum antibiotics in TNF^ΔARE/+ mice. Antibiotic-treated mice had reduced gut-joint IEL migration, contained fewer Il-17A and TNF competent CD4+ T cells, and lessened joint pathology compared to untreated littermate controls. Together these results demonstrate that pro-inflammatory colon-derived IELs can exacerbate inflammatory responses in the joint through systemic trafficking, and that interference with this process through gut-targeted approaches has therapeutic potential in SpA.

Blood HDAC4 Variation Links With Disease Activity and Response to Tumor Necrosis Factor Inhibitor and Regulates CD4+ T Cell Differentiation in Ankylosing Spondylitis

Purpose

Histone deacetylase 4 (HDAC4) regulates the progression of autoimmune diseases. This study aimed to further investigate the correlation between HDAC4 and Th cells, inflammation, disease activity, and treatment response in patients with ankylosing spondylitis (AS).

Methods

A total of 132 active patients with AS were enrolled, of whom 54 patients received TNF inhibitor (TNFi) and 78 patients received NSAID. Serum HDAC4 was measured by ELISA in patients with AS before treatment (W0) and at week (W)4, W8, and W12 after treatment. Meanwhile, serum HDAC4 was detected in 30 patients with osteoarthritis and in 30 healthy controls (HCs) by ELISA. Besides, naïve CD4⁺ T cells from patients with AS were isolated, followed by modulation of HDAC4 and then polarization toward Th1, Th2, and Th17.

Results

Histone deacetylase 4 was reduced in patients with AS compared with HCs and patients with osteoarthritis (both P < 0.01). In patients with AS, HDAC4 was negatively correlated with TNF (P < 0.001), IL-1β (P = 0.003), Th17 proportion (P = 0.008), C-reactive protein (P < 0.001), and ASDAS (P = 0.038), but not with IL-6, Th1 proportion, or other characteristics. Meanwhile, HDAC4 increased from W0 to W12 (P < 0.001); HDAC4 at W8 (P = 0.014) and W12 (P = 0.006) was raised in ASAS40-response patients than ASAS40-non-response patients; further subgroup analysis showed that HDAC4 at W12 was higher in ASAS40-response patients than ASAS40-non-response patients (P = 0.016) in the TNFi-treated group, but not in the NSAID-treated group. In addition, HDAC4 negatively regulated the polarization of naïve CD4⁺ T cells toward Th17 (P < 0.01), but not Th1 or Th2.

Conclusion

Histone deacetylase 4 is associated with lower inflammation, and the disease activity negatively regulates Th17 polarization, whose increment after treatment reflects favorable outcomes in patients with AS.

The Treatment with Interleukin 17 Inhibitors and Immune-Mediated Inflammatory Diseases

IL-17 inhibitors (IL-17i) are medicines used to treat dermatological and rheumatic diseases They belong to a class of medicines called biological disease-modifying anti-rheumatic drugs (bDMARDs). This class of drugs has had a major impact on the therapy of autoimmune diseases, being much safer and more effective than treatment with small molecules. At the same time, they have highly beneficial effects on skin and joint changes, and their efficacy has been extensively monitored and demonstrated in numerous clinical trials. More and more such drugs are still being discovered today to ensure the best possible treatment of these patients, but more frequently and relatively constantly three agents are used. Two of them (Secukinumab and Ixekizumab) inhibit IL-17A directly, and the third, Brodamulab, inhibits the IL-17A receptor. Although they are extremely effective in the treatment of these diseases, sometimes their administration has been associated with paradoxical effects, i.e., there is an exacerbation of the inflammatory process. Tough, clinical trials of IL-17i have described cases of exacerbation or even onset of inflammatory bowel disease (IBD), such as Crohn's disease and ulcerative colitis, after administration of these drugs in patients previously diagnosed with psoriasis (PS), psoriatic arthritis (PsA), or ankylosing spondylitis (AS). The pathophysiological mechanism of action is not well understood at present. One explanation would be that this hyperreactive inflammatory process would be triggered by Interferon 1 derived from dendritic plasma cells. Even though there are many reports in the recent literature about the role of IL17i in the onset of IBD, conclusions of studies do not converge. Some of them show an increased incidence of IBD in patients treated with IL17i, while some others affirm their safety of them. In the near future we will surely have more data emerging from ongoing meta-analyses regarding safety of use IL17i in patients who are at risk of developing IBD. Clinical and paraclinical evaluation (inflammatory intestinal markers) are carefully advised before recommending treatment with IL-17i and after initiation of treatment, and prospective surveillance by clinical and biomarkers of patients treated with IL-17i is absolutely essential to capture the onset of IBD.

Immunopathophysiology of Juvenile Spondyloarthritis (jSpA): The "Out of the Box" View on Epigenetics, Neuroendocrine Pathways and Role of the Macrophage Migration Inhibitory Factor (MIF)

Juvenile spondyloarthritis (jSpA) is a an umbrella term for heterogeneous group of related seronegative inflammatory disorders sharing common symptoms. Although it mainly affects children and adolescents, it often remains active during adulthood. Genetic and environmental factors are involved in its occurrence, although the exact underlying immunopathophysiology remains incompletely elucidated. Accumulated evidence suggests that, in affected patients, subclinical gut inflammation caused by intestinal dysbiosis, is pivotal to the future development of synovial-entheseal complex inflammation. While the predominant role of IL17/23 axis, TNF-α, and IL-7 in the pathophysiology of SpA, including jSpA, is firmly established, the role of the cytokine macrophage migration inhibitory factor (MIF) is generally overlooked. The purpose of this review is to discuss and emphasize the role of epigenetics, neuroendocrine pathways and the hypothalamic-pituitary (HPA) axis, and to propose a novel hypothesis of the role of decreased NLRP3 gene expression and possibly MIF in the early phases of jSpA development. The decreased NLRP3 gene expression in the latter, due to hypomethylation of promotor site, is (one of) the cause for inflammasome malfunction leading to gut dysbiosis observed in patients with early jSpA. In addition, we highlight the role of MIF in the complex innate, adaptive cellular and main effector cytokine network, Finally, since treatment of advanced bone pathology in SpA remains an unmet clinical need, I suggest possible new drug targets with the aim to ultimately improve treatment efficacy and long-term outcome of jSpA patients.

Complexity of enthesitis and new bone formation in ankylosing spondylitis: current understanding of the immunopathology and therapeutic approaches

Despite increasing availability of treatments for spondyloarthritis (SpA) including tumour necrosis factor (TNF) and interleukin-17 (IL-17) inhibitors, there is no established treatment that abates new bone formation (NBF) in ankylosing spondylitis (AS), a subset of SpA. Recent research on TNF has revealed the increased level of transmembrane TNF in the joint tissue of SpA patients compared to that of rheumatoid arthritis patients, which appears to facilitate TNF-driven osteo-proliferative changes in AS. In addition, there is considerable interest in the central role of IL-23/IL-17 axis in type 3 immunity and the therapeutic potential of blocking this axis to ameliorate enthesitis and NBF in AS. AS immunopathology involves a variety of immune cells, including both innate and adoptive immune cells, to orchestrate the immune response driving type 3 immunity. In response to external stimuli of inflammatory cytokines, local osteo-chondral progenitor cells activate intra-cellular anabolic molecules and signals involving hedgehog, bone morphogenetic proteins, receptor activator of nuclear factor kappa-B ligand, and Wnt pathways to promote NBF in AS. Here, we provide an overview of the current immunopathology and future directions for the treatment of enthesitis and NBF associated with AS.

IL17F: A Possible Risk Marker for Spondyloarthritis in HLA-B*27 Negative Brazilian Patients

HLA-B*27 is an important marker for spondyloarthritis (SpA), however, many SpA patients are HLA-B*27 negative. Thus, the aim of this study was to investigate the influence of IL17, TNF and VDR gene polymorphisms in SpA patients who were HLA-B*27 negative. This case-control study was conducted in 158 patients [102 patients with ankylosing spondylitis (AS) and 56 with psoriatic arthritis (PsA)] and 184 controls. HLA-B*27 genotyping was performed using PCR-SSP and IL17A (rs2275913), IL17F (rs763780), TNF-308 (rs1800629), TNF-238 (rs361525), FokI C>T (rs2228570), TaqI C>T (rs731236), ApaI A>C (rs7975232), and BsmI C>T (rs1544410) using PCR-RFLP. Statistical analyses were performed by Chi-square and logistic regression using OpenEpi and SNPStats software. The IL17F C allele frequency was higher in patients with SpA, AS and PsA compared to controls. The IL17F T/C genotype frequency was higher in SpA patients in an overdominant inheritance model and when men and women were separately analyzed. IL17A_IL17F AC haplotype was significantly associated to the risk for SpA patients. As for VDR, the ApaI a/a was a potential risk factor for SpA in men. In conclusion, IL17F C variant contributed to the risk of SpA in Brazilian patients who were HLA-B*27 negative and could be a potential marker for SpA.

Multi 'Omics Analysis of Intestinal Tissue in Ankylosing Spondylitis Identifies Alterations in the Tryptophan Metabolism Pathway

Intestinal microbial dysbiosis, intestinal inflammation, and Th17 immunity are all linked to the pathophysiology of spondyloarthritis (SpA); however, the mechanisms linking them remain unknown. One potential hypothesis suggests that the dysbiotic gut microbiome as a whole produces metabolites that influence human immune cells. To identify potential disease-relevant, microbiome-produced metabolites, we performed metabolomics screening and shotgun metagenomics on paired colon biopsies and fecal samples, respectively, from subjects with axial SpA (axSpA, N=21), Crohn's disease (CD, N=27), and Crohn's-axSpA overlap (CD-axSpA, N=12), as well as controls (HC, N=24). Using LC-MS based metabolomics of 4 non-inflamed pinch biopsies of the distal colon from subjects, we identified significant alterations in tryptophan pathway metabolites, including an expansion of indole-3-acetate (IAA) in axSpA and CD-axSpA compared to HC and CD and indole-3-acetaldehyde (I3Ald) in axSpA and CD-axSpA but not CD compared to HC, suggesting possible specificity to the development of axSpA. We then performed shotgun metagenomics of fecal samples to characterize gut microbial dysbiosis across these disease states. In spite of no significant differences in alpha-diversity among the 4 groups, our results confirmed differences in gene abundances of numerous enzymes involved in tryptophan metabolism. Specifically, gene abundance of indolepyruvate decarboxylase, which generates IAA and I3Ald, was significantly elevated in individuals with axSpA while gene abundances in HC demonstrated a propensity towards tryptophan synthesis. Such genetic changes were not observed in CD, again suggesting disease specificity for axSpA. Given the emerging role of tryptophan and its metabolites in immune function, altogether these data indicate that tryptophan metabolism into I3Ald and then IAA is one mechanism by which the gut microbiome potentially influences the development of axSpA.

The gut-joint axis in spondyloarthritis: immunological, microbial, and clinical insights

The strong genetic and clinical overlaps between spondyloarthritis (SpA) and inflammatory bowel disease (IBD) have placed much needed focus on the gut-joint axis of inflammation in SpA, leading to three key hypotheses that attempt to unravel this complex relationship. The arthritogenic peptide hypothesis and the aberrant cellular trafficking hypothesis have been put forth to rationalize the manner by which the innate and adaptive immune systems cooperate and converge during SpA pathogenesis. The bacterial dysbiosis hypothesis discusses how changes in the microbiome lead to architectural and immunological consequences in SpA. These theories are not mutually exclusive, but can provide an explanation as to why subclinical gut inflammation may sometimes precede joint inflammation in SpA patients, thereby implying a causal relationship. Such investigations will be important in informing therapeutic decisions which may be common to both SpA and IBD. However, these hypotheses can also offer insights for a coincident inflammatory relationship between the gut and the joint, particularly when assessing the immunological players involved. Insights from understanding how these systems might affect the gut and joint differently will be equally imperative to address where the therapeutic differences lie between the two diseases. Collectively, this knowledge has practical implications in predicting the likelihood of IBD development in SpA or presence of coincident SpA-IBD, uncovering novel therapeutic targets, and redesigning currently approved treatments. It is evident that a multidisciplinary approach between the rheumatology and gastroenterology fields cannot be ignored, when it comes to the care of SpA patients at risk of IBD or vice versa.

Effect of dexmedetomidine on CD4+ T cells and programmed cell death protein-1 in postoperative analgesia: a prospective, randomized, controlled study

BACKGROUND

Surgical trauma inhibits cellular immunity. Dexmedetomidine produces opioid-sparing effect and an impact on immune response.

METHODS

Eighty-six surgical patients were enrolled and received postoperative patient-controlled intravenous analgesia (PCIA) with either fentanyl alone (fentanyl group) or combined with dexmedetomidine (dexmedetomidine group). The percentages of T helper cells (Th1, Th2, and Th17) and regulatory T (Treg) cells, expression levels of programmed cell death protein-1 (PD-1) and its ligand (PD-L1) on the CD4⁺ T cells, and plasma levels of the cytokines were tested. Postoperative pain was measured by numerical rating scale (NRS), including NRS at rest (NRSR) and movement (NRSM).

RESULTS

In dexmedetomidine group, Th1 cells were increased significantly at 24 and 48 h following surgery (P=0.011 and P=0.013, respectively) and Treg cells were significantly higher at 48 h postoperatively (P=0.013). PD-1 was significantly lower in dexmedetomidine group at 24 h postoperatively (P=0.046) and interleukin 4 (IL-4) and IL-6 were significantly decreased at 48 h postoperatively (P=0.024 and P=0.035, respectively). Compared with fentanyl group, NRSR scores were lower in dexmedetomidine group at 24 h following surgery (P=0.018) and NRSR and NRSM scores were lower at 48 h postoperatively (P=0.007 and P=0.011, respectively). NRSR exhibited negative correlations with Th1 cells in fentanyl group and dexmedetomidine group (P=0.003 and P=0.005, respectively).

CONCLUSIONS

Dexmedetomidine increases the differentiation of Th1 and Treg cells and reduces the expression of PD-1 on CD4⁺ T cells. Dexmedetomidine may assist to ameliorate postoperative pain and attenuate proinflammatory response. There might be a negative correlation between pain and Th1 cells.

The association between Candida infection and ankylosing spondylitis: a population-based matched cohort study

AIMS

To explore whether newly diagnosed Candida infection increases the risk of developing ankylosing spondylitis (AS).

METHODS AND MATERIALS

We investigated 61,550 patients with newly diagnosed Candida infection between 1997 and 2013 from the Taiwan National Health Insurance Research Datasets to conduct a population-based matched-cohort study. Controls were 61,550 subjects without Candida infection and propensity score matched with the Candida exposure cohort. The follow-up period was defined as month from the initial diagnosis of Candida infection (or nested index date for controls) to the date of AS, or 31 December 2013. We used Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the occurrence of AS.

RESULTS

The incidence rates of AS in the Candida group and comparison group were respectively 4.58 and 3.88 per 100,000 person-months. The adjusted HR (95% CI) of AS for the Candida group was 1.19 (0.99-1.44) compared to the control group after adjustment for age, gender and all covariates (95% CI = 1.77-2.27). However, an adjusted hazard ratio (aHR) of 1.77-fold (95% CI = 1.26-2.53) significant increase in the risk of developing AS was observed after 6 years of follow-up, when exposure to Candida was at baseline. The effect of Candida infection was significantly time varying (p value for interaction between follow-up period and Candida infection is .018).

CONCLUSIONS

A risk of AS was found after Candida infection, and a year of follow-up acts as an effect modifier between the Candida infection and risk of AS. Key messages What is already known on this subject? Links between spondyloarthritis and fungal infections have been found in animal studies before. What does this study add? Our study demonstrated that Candida infection is an independent risk factor for developing ankylosing spondylitis in terms of gender, age and relevant variables and comorbidities. A risk of ankylosing spondylitis was found after Candida infection, and year of follow-up acts as an effect modifier between the Candida infection and risk of AS. Clinicians should be aware of possible Candida infection in managing patients with ankylosing spondylitis. Implications: Clinicians must pay greater attention to patients with newly diagnosed Candida infection. Specifically, they should conduct tests for ankylosing spondylitis. Further research is needed to examine if and how treatment of Candida infection alleviates symptoms of AS.

Paradoxical gastrointestinal effects of interleukin-17 blockers

Secukinumab, ixekizumab and brodalumab are monoclonal antibody therapies that inhibit interleukin (IL)-17 activity and are widely used for the treatment of psoriasis, psoriatic arthritis and ankylosing spondylitis. The promising efficacy results in dermatology and rheumatology prompted the evaluation of these drugs in Crohn's disease and ulcerative colitis, but the onset of paradoxical events (disease exacerbation after treatment with a theoretically curative drug) prevented their approval in patients with inflammatory bowel diseases (IBDs). To date, the pathophysiological mechanisms underlying these paradoxical effects are not well defined, and there are no clear guidelines for the management of patients with disease flare or new IBD onset after anti-IL-17 drug therapy. In this review, we summarise the literature on putative mechanisms, the clinical digestive effects after therapy with IL-17 inhibitors and provide guidance for the management of these paradoxical effects in clinical practice.

HLA associations in inflammatory arthritis: emerging mechanisms and clinical implications

Our understanding of the mechanisms underlying HLA associations with inflammatory arthritis continues to evolve. Disease associations have been refined, and interactions of HLA genotype with other genes and environmental risk factors in determining disease risk have been identified. This Review provides basic information on the genetics and molecular function of HLA molecules, as well as general features of HLA associations with disease. Evidence is discussed regarding the various peptide-dependent and peptide-independent mechanisms by which HLA alleles might contribute to the pathogenesis of three types of inflammatory arthritis: rheumatoid arthritis, spondyloarthritis and systemic juvenile idiopathic arthritis. Also discussed are HLA allelic associations that shed light on the genetic heterogeneity of inflammatory arthritides and on the relationships between adult and paediatric forms of arthritis. Clinical implications range from improved diagnosis and outcome prediction to the possibility of using HLA associations in developing personalized strategies for the treatment and prevention of these diseases.

[New directions of pharmacotherapy of immune - inflammatory rheumatic diseases]

Deciphering immunopathogenesis, expanding the scope of diagnostics and developing new methods for treating human autoimmune diseases are among the priority areas of XXI century medicine. Particularly widely autoimmune pathology is presented in immunoinflammatory rheumatic diseases (IIRD), such as rheumatoid arthritis, systemic lupus erythematosus, systemic scleroderma, systemic vasculitis associated with the synthesis of antineutrophilic cytoplasmic antibodies, Sjogren's syndrome, idiopathic inflammatory myopathies and other other types of others. Deciphering the pathogenesis mechanisms of IIRD created the prerequisites for improving pharmacotherapy, which in the future should lead to a dramatic improvement in the prognosis for these diseases. The review discusses new approaches to IIRD pharmacotherapy associated with the inhibition of tumor necrosis factor-α, interleukin-6 (IL-6), IL-1β, IL-17, IL-23, and the prospects for using Janus kinase inhibitors, depending on the prevailing pathogenesis mechanisms - autoimmunity or autoinflammation.

The role of IL-17A in axial spondyloarthritis and psoriatic arthritis: recent advances and controversies

Although the pathogenic mechanisms underlying axial spondyloarthritis (axSpA) and psoriatic arthritis (PsA) are not fully elucidated, several lines of evidence suggest that immune responses mediated by interleukin 17A (IL-17A) play a pivotal role in both diseases. This is best highlighted by the significant clinical efficacy shown with inhibitors of IL-17A in treating axSpA and PsA. Nevertheless, a number of knowledge gaps exist regarding the role of IL-17A in the pathophysiology of spondyloarthritis in man, including its cellular origin, its precise role in discrete disease processes such enthesitis, bone erosion, and bone formation, and the reasons for the discrepant responses to IL-17A inhibition observed in certain other spondyloarthritis manifestations. In this review, we focus on the latest data from studies investigating the role of IL-17A in ankylosing spondylitis (AS) and PsA that build on existing and emerging scientific knowledge in the field. Key remaining research questions are also highlighted to guide future research.