The HLA-B27 gene is a major risk factor for clinical diseases including ankylosing spondylitis, acute anterior uveitis, reactive arthritis, and psoriatic arthritis, but its mechanism of risk ...enhancement is not completely understood. The gut microbiome has recently been shown to influence several HLA-linked diseases. However, the role of HLA-B27 in shaping the gut microbiome has not been previously investigated. In this study, we characterize the differences in the gut microbiota mediated by the presence of the HLA-B27 gene. We identified differences in the cecal microbiota of Lewis rats transgenic for HLA-B27 and human β2-microglobulin (hβ2m), compared with wild-type Lewis rats, using biome representational in situ karyotyping (BRISK) and 16S rRNA gene sequencing. 16S sequencing revealed significant differences between transgenic animals and wild type animals by principal coordinates analysis. Further analysis of the data set revealed an increase in Prevotella spp. and a decrease in Rikenellaceae relative abundance in the transgenic animals compared to the wild type animals. By BRISK analysis, species-specific differences included an increase in Bacteroides vulgatus abundance in HLA-B27/hβ2m and hβ2m compared to wild type rats. The finding that HLA-B27 is associated with altered cecal microbiota has not been shown before and can potentially provide a better understanding of the clinical diseases associated with this gene.
Objective
We undertook this study to examine the functional basis for epistasis between endoplasmic reticulum aminopeptidase 1 (ERAP1) and HLA–B27 in experimental spondyloarthritis (SpA).
Methods
...ERAP1–knockout rats were created using genome editing and bred with HLA–B27/human β2‐microglobulin–transgenic (HLA–B27‐Tg) rats and HLA–B7‐Tg rats. The effects of ERAP1 deficiency on HLA allotypes were determined using immunoprecipitation and immunoblotting, flow cytometry, allogeneic T cell proliferation assays, and gene expression analyses. Animals were examined for clinical features of disease, and tissue was assessed by histology.
Results
ERAP1 deficiency increased the ratio of folded to unfolded (β2m‐free) HLA–B27 heavy chains, while having the opposite effect on HLA–B7. Furthermore, in rats with ERAP1 deficiency, HLA–B27 misfolding was reduced, while free HLA–B27 heavy chain dimers on the cell surface and monomers were increased. The effects of ERAP1 deficiency persisted during up‐regulation of HLA–B27 and led to a reduction in endoplasmic reticulum stress. ERAP1 deficiency reduced the prevalence of arthritis in HLA–B27‐Tg rats by two‐thirds without reducing gastrointestinal inflammation. Dendritic cell abnormalities attributed to the presence of HLA–B27, including reduced allogeneic T cell stimulation and loss of CD103‐positive/major histocompatibility complex class II–positive cells, were not rescued by ERAP1 deficiency, while excess Il23a up‐regulation was mitigated.
Conclusion
ERAP1 deficiency reduced HLA–B27 misfolding and improved folding while having opposing effects on HLA–B7. The finding that HLA–B27‐Tg rats had partial protection against SpA in this study is consistent with genetic evidence that loss‐of‐function and/or reduced expression of ERAP1 reduces the risk of ankylosing spondylitis. Functional studies support the concept that the effects of ERAP1 on HLA–B27 and SpA may be a consequence of how peptides affect the biology of this allotype rather than their role as antigenic determinants.
IL-17A is a central driver of spondyloarthritis (SpA), its production was originally proposed to be IL-23 dependent. Emerging preclinical and clinical evidence suggests, however, that IL-17A and ...IL-23 have a partially overlapping but distinct biology. We aimed to assess the extent to which IL-17A-driven pathology is IL-23 dependent in experimental SpA. Experimental SpA was induced in HLA-B27/Huβ2m transgenic rats, followed by prophylactic or therapeutic treatment with an anti-IL23R antibody or vehicle control. Spondylitis and arthritis were scored clinically and hind limb swelling was measured. Draining lymph node cytokine expression levels were analyzed directly
, and IL-17A protein was measured upon restimulation with PMA/ionomycin. Prophylactic treatment with anti-IL23R completely protected against the development of both spondylitis and arthritis, while vehicle-treated controls did develop spondylitis and arthritis. In a therapeutic study, anti-IL23R treatment failed to reduce the incidence or decrease the severity of experimental SpA. Mechanistically, expression of downstream effector cytokines, including IL-17A and IL-22, was significantly suppressed in anti-IL23R versus vehicle-treated rats in the prophylactic experiments. Accordingly, the production of IL-17A upon restimulation was reduced. In contrast, there was no difference in IL-17A and IL-22 expression after therapeutic anti-IL23R treatment. Targeting the IL-23 axis during the initiation phase of experimental SpA-but not in established disease-inhibits IL-17A expression and suppresses disease, suggesting the existence of IL-23-independent IL-17A production. Whether IL-17A can be produced independent of IL-23 in human SpA remains to be established.
Objective
It remains unclear if and how inflammation and new bone formation in spondyloarthritis (SpA) are coupled. We undertook this study to assess the hypothesis that interleukin‐17A (IL‐17A) is a ...pivotal driver of both processes.
Methods
The effect of tumor necrosis factor (TNF) and IL‐17A on osteogenesis was tested in an osteoblastic differentiation assay using SpA fibroblast‐like synoviocytes (FLS) differentiated with dexamethasone, β‐glycophosphatase, and ascorbic acid. IL‐17A blockade was performed in HLA–B27/human β2‐microglobulin (hβ2m)–transgenic rats, which served as a model for SpA in both prophylactic and therapeutic settings. Inflammation and new bone formation were evaluated by micro–computed tomography imaging, histologic analysis, and gene expression profiling.
Results
TNF and IL‐17A significantly increased in vitro osteoblastic differentiation. In vivo, prophylactic blockade of IL‐17A significantly delayed spondylitis and arthritis development and decreased arthritis severity. Anti–IL‐17A treatment was also associated with prevention of bone loss and periosteal new bone formation. Therapeutic targeting of IL‐17A after the initial inflammatory insult also significantly reduced axial and peripheral joint inflammation. This treatment was again associated with a marked reduction in spinal and peripheral structural damage, including new bone formation. RNA sequencing of target tissue confirmed that IL‐17A is a key driver of the molecular signature of disease in this model and that therapeutic anti–IL‐17A treatment reversed the inflammatory signature and the selected gene expression related to bone damage.
Conclusion
Both prophylactic and therapeutic inhibition of IL‐17A diminished inflammation and new bone formation in HLA‐B27/hβ2m–transgenic rats. Taken together with the ability of IL‐17A to promote osteoblastic differentiation of human SpA FLS, these data suggest a direct link between IL‐17A–driven inflammation and pathologic new bone formation in SpA.
•Axial spondyloarthritis (SpA) has challenging diagnosis due to temporal findings.•We studied the diagnostic value of 3 T multiparametric combined MR imaging in SpA.•41 patients were enrolled to ...assess the detailed imaging and lab findings.•MRI protocol was able to provide extensive findings helpful in SpA diagnosis.•It provides a better insight to clinicians for diagnosis and monitoring of SpA.
Axial spondyloarthritis (SpA) is a group of diseases with temporally disseminated symptoms and clinical signs, which render the diagnosis challenging. Laboratory and MRI findings are used in addition for confirming the diagnosis and evaluation of disease activity. The purpose of this study was to evaluate clinically suspected axial SpA to determine the technical success of a multiparametric and 3D rheumatology lumbosacral MR imaging (MRLI) protocol and to assess the disease distribution, inter-reader reliability, and impact on patient management.
A consecutive series of patients with clinical suspicion of axial SpA were included. Two rheumatologists recorded the clinical findings and disease activity on a confidence scale before and after MRLI. Two musculoskeletal (MSK) radiologists read the imaging data including enthesitis, arthritis, osseous lesions, ADC values, and enhancement. Prevalence-adjusted and bias-adjusted kappa (PABAK), ICC and Fisher exact test were calculated.
There were 41 patients including 31 females and 10 males with ages of 41 ± 10 and 41 ± 12 (mean ± SD), respectively. The spine T2W imaging received the highest quality scores followed by whole abdomen-pelvis 3D-T2W imaging, 3D-CEMR (contrast-enhanced MRI), and DWI. On spine imaging, acute and chronic lesions of lumbar spine and sacroiliac joints were seen in 4/41, 18/41 and 6/41, and 27/41 of the patients, respectively. Several additional enthesopathy lesions were seen on the whole abdomen-pelvis 3D sequence. ADC value of bone lesions was different 0.95 ± 0.23 (mean ± SD) than normal bone (0.20 ± 0.1). PABAK for acute and chronic findings ranged 0.70–1.0 and 0.41-0.51, respectively. Imaging changed the diagnosis in 17 of 41 patients. No association was noted with respect to treatment change (p = 1) or clinical response (p = 0.2).
Multiparametric lumbosacral MR imaging is a technically successful modality to identify multiple spinal and additional extraspinal sites of involvement in SpA, which are helpful in establishing the diagnosis of axial SpA. Larger patient population study is warranted to evaluate further impact on the treatment efficacy.
Spondyloarthritis (SpA) is characterized by inflammation, articular bone erosions and pathologic new bone formation. Targeting TNFα or IL-17A with current available therapies reduces inflammation in ...SpA, however, treatment of the bone pathology in SpA remains an unmet clinical need. Activation of the mammalian target Of rapamycin (mTOR) promotes IL-17A expression and osteogenesis. Therefore, the inhibition of mTOR (with rapamycin) could be a promising therapeutic avenue in SpA.
To investigate the effect of blocking mTOR on inflammation, bone erosions and new bone formation in SpA.
Peripheral blood mononuclear cells (PBMCs) from patients with SpA were stimulated with anti-CD3/CD28 in the presence or absence of rapamycin and the resulting cytokine expression was assessed. Fibroblast-like synoviocytes (FLS) from SpA patients were assessed for osteogenic differentiation potential in conditions with TNFα, IL-17A, or TNFα plus IL-17A, in the presence or absence of rapamycin. HLA-B27/Huβ2m transgenic rats were immunized with low dose heat-inactivated
, treated with 1.5 mg/kg rapamycin prophylactically or therapeutically and monitored for arthritis and spondylitis. Histology and mRNA analysis were performed after 5 weeks of treatment to assess inflammation and bone pathology.
TNFα and IL-17A protein production by SpA PBMCs was inhibited in the presence of rapamycin. Rapamycin also inhibited osteogenic differentiation of human SpA FLS.
analysis of SpA synovial biopsies indicated activation of the mTOR pathway in the synovial tissue of SpA patients.
, prophylactic treatment of HLA-B27/Huβ2m transgenic rats with rapamycin significantly inhibited the development and severity of inflammation in peripheral joints and spine (arthritis and spondylitis), with histological evidence of reduced bone erosions and new bone formation around peripheral joints. In addition, therapeutic treatment with rapamycin significantly decreased severity of arthritis and spondylitis, with peripheral joint histology showing reduced inflammation, bone erosions and new bone formation.
mRNA expression was decreased in the metacarpophalangeal joints after rapamycin treatment.
mTOR blockade inhibits IL-17A and TNFα production by PBMCs, and osteogenic differentiation of FLS from patients with SpA
. In the HLA-B27 transgenic rat model of SpA, rapamycin inhibits arthritis and spondylitis development and severity, reduces articular bone erosions, decreases pathologic new bone formation and suppresses IL-17A expression. These results may support efforts to evaluate the efficacy of targeting the mTOR pathway in SpA patients.
HLA-B27 is a class I major histocompatibility (MHC-I) allele that confers susceptibility to the rheumatic disease ankylosing spondylitis (AS) by an unknown mechanism. ERAP1 is an aminopeptidase that ...trims peptides in the endoplasmic reticulum for binding to MHC-I molecules. ERAP1 shows genetic epistasis with HLA-B27 in conferring susceptibility to AS. Male HLA-B27 transgenic rats develop arthritis and serve as an animal model of AS, whereas female B27 transgenic rats remain healthy. We used large scale quantitative mass spectrometry to identify over 15,000 unique HLA-B27 peptide ligands, isolated after immunoaffinity purification of the B27 molecules from the spleens of HLA-B27 transgenic rats. Heterozygous deletion of Erap1, which reduced the Erap1 level to less than half, had no qualitative or quantitative effects on the B27 peptidome. Homozygous deletion of Erap1 affected approximately one-third of the B27 peptidome but left most of the B27 peptidome unchanged, suggesting the possibility that some of the HLA-B27 immunopeptidome is not processed in the presence of Erap1. Deletion of Erap1 was permissive for the AS-like phenotype, increased mean peptide length and increased the frequency of C-terminal hydrophobic residues and of N-terminal Ala, Ser, or Lys. The presence of Erap1 increased the frequency of C-terminal Lys and Arg, of Glu and Asp at intermediate residues, and of N-terminal Gly. Several peptides of potential interest in AS pathogenesis, previously identified in human cell lines, were isolated. However, rats susceptible to arthritis had B27 peptidomes similar to those of non-susceptible rats, and no peptides were found to be uniquely associated with arthritis. Whether specific B27-bound peptides are required for AS pathogenesis remains to be determined. Data are available via ProteomeXchange with identifier PXD005502.
Objective
In HLA–B27–transgenic rats, the development of a disorder that mimics spondyloarthritis (SpA) is highly correlated with dendritic cell (DC) dysfunction. The present study was undertaken to ...analyze the underlying mechanisms of this via transcriptome analysis.
Methods
Transcriptome analysis of ex vivo–purified splenic CD103+CD4+ DCs from B27‐transgenic rats and control rats was performed. Transcriptional changes in selected genes were confirmed by quantitative reverse transcriptase–polymerase chain reaction. A meta‐analysis of our rat data and published data on gene expression in macrophages from ankylosing spondylitis (AS) patients was further performed.
Results
Interferon (IFN) signaling was the most significantly affected pathway in DCs from B27‐transgenic rats; the majority of genes connected to IFN were underexpressed in B27‐transgenic rats as compared to controls. This pattern was already present at disease onset, persisted over time, and was conserved in 2 disease‐prone B27‐transgenic rat lines. In DCs from B27‐transgenic rats, we further found an up‐regulation of suppressor of cytokine signaling 3 (which may account for reverse IFN signaling) and a down‐regulation of interleukin‐27 (a cytokine that opposes Th17 differentiation and promotes Treg cells). The meta‐analysis of data on conventional DCs from rats and data on monocyte‐derived macrophages from humans revealed 7 IFN‐regulated genes that were negatively regulated in both human and rat SpA (i.e., IRF1, STAT1, CXCL9, CXCL10, IFIT3, DDX60, and EPSTI1).
Conclusion
Our results suggest that expression of HLA–B27 leads to a defect in IFNγ signaling in antigen‐presenting cells in both B27‐transgenic rats and SpA patients, which may result in Th17 expansion and Treg cell alteration (as shown in B27‐transgenic rats) and contribute to disease pathogenesis.
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