The association between refractory plantar fasciitis and insertional Achilles tendinopathy and peripheral spondyloarthritis: a report of human leukocyte antigen B-27 investigation and treatment outcome

PURPOSE

This study aimed to determine the presence of peripheral spondyloarthritis and investigate the clinical characteristics of patients with concurrent peripheral spondyloarthritis in those presenting with refractory plantar fasciitis and Achilles tendinopathy by conducting human leukocyte antigen B-27 (HLA-B27) testing.

METHODS

This retrospective study aimed to investigate patients who complained of persistent pain and significant limitations in daily activities due to their respective foot pain, despite receiving conservative treatment for over one year under the diagnosis of plantar fasciitis or insertional Achilles tendinopathy. The study included 63 patients who underwent HLA-B27 testing. The patients were classified into two groups based on the presence or absence of HLA-B27 positivity. The Mann-Whitney U test assessed significant relationships between continuous variables, and the chi-square test was used to compare categorical variables.

RESULTS

Among the 63 included patients, HLA-B27 positivity was confirmed in 11 patients (17.5%), which was significantly associated with a lower average age (22.8 years versus 31.7 years, P = 0.01) and a substantially lower proportion of females compared to HLA-B27-negative patients (9.1% vs. 25.0%, P = 0.001). Ten of the 11 patients initiated treatment with conventional synthetic disease-modifying antirheumatic drugs (DMARDs) combined with oral steroids as the first-line medication after being diagnosed as HLA-B27 positive. Six patients experienced pain relief with the first-line medication (60%). Four patients who did not achieve pain control with the first-line medication received tumour necrosis factor-alpha inhibitors as the second-line medication. Two patients experienced pain relief, while two experienced reduced but persistent pain.

CONCLUSIONS

Among the patients with "refractory" plantar fasciitis and insertional Achilles tendinopathy, 17.5% were diagnosed with peripheral spondyloarthritis. Patients diagnosed with peripheral spondyloarthritis had a higher proportion of men and relatively younger mean age compared to those without the diagnosis. Approximately 70% of these patients achieved symptom improvement in foot and ankle joints by taking conventional synthetic DMARDs, TNF-α inhibitors, or both appropriate for spondyloarthritis.

Paradoxical Effects of Endoplasmic Reticulum Aminopeptidase 1 Deficiency on HLA-B27 and Its Role as an Epistatic Modifier in Experimental Spondyloarthritis

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 (β2 m-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.

Modulation of Natural HLA-B*27:05 Ligandome by Ankylosing Spondylitis-associated Endoplasmic Reticulum Aminopeptidase 2 (ERAP2)

The HLA-B*27:05 allele and the endoplasmic reticulum-resident aminopeptidases are strongly associated with AS, a chronic inflammatory spondyloarthropathy. This study examined the effect of ERAP2 in the generation of the natural HLA-B*27:05 ligandome in live cells. Complexes of HLA-B*27:05-bound peptide pools were isolated from human ERAP2-edited cell clones, and the peptides were identified using high-throughput mass spectrometry analyses. The relative abundance of a thousand ligands was established by quantitative tandem mass spectrometry and bioinformatics analysis. The residue frequencies at different peptide position, identified in the presence or absence of ERAP2, determined structural features of ligands and their interactions with specific pockets of the antigen-binding site of the HLA-B*27:05 molecule. Sequence alignment of ligands identified with species of bacteria associated with HLA-B*27-dependent reactive arthritis was performed. In the absence of ERAP2, peptides with N-terminal basic residues and minority canonical P2 residues are enriched in the natural ligandome. Further, alterations of residue frequencies and hydrophobicity profile at P3, P7, and PΩ positions were detected. In addition, several ERAP2-dependent cellular peptides were highly similar to protein sequences of arthritogenic bacteria, including one human HLA-B*27:05 ligand fully conserved in a protein from Campylobacter jejuni These findings highlight the pathogenic role of this aminopeptidase in the triggering of AS autoimmune disease.

Substantial Influence of ERAP2 on the HLA-B*40:02 Peptidome: Implications for HLA-B*27-Negative Ankylosing Spondylitis

HLA-B*40:02 is one of a few major histocompatibility complex class I (MHC-I) molecules associated with ankylosing spondylitis (AS) independently of HLA-B*27. The endoplasmic reticulum aminopeptidase 2 (ERAP2), an enzyme that process MHC-I ligands and preferentially trims N-terminal basic residues, is also a risk factor for this disease. Like HLA-B*27 and other AS-associated MHC-I molecules, HLA-B*40:02 binds a relatively high percentage of peptides with ERAP2-susceptible residues. In this study, the effects of ERAP2 depletion on the HLA-B*40:02 peptidome were analyzed. ERAP2 protein expression was knocked out by CRISPR in the transfectant cell line C1R-B*40:02, and the differences between the peptidomes from the wild-type and ERAP2-KO cells were determined by label-free quantitative comparisons. The qualitative changes dependent on ERAP2 affected about 5% of the peptidome, but quantitative changes in peptide amounts were much more substantial, reflecting a significant influence of this enzyme on the generation/destruction balance of HLA-B*40:02 ligands. As in HLA-B*27, a major effect was on the frequencies of N-terminal residues. In this position, basic and small residues were increased, and aliphatic/aromatic ones decreased in the ERAP2 knockout. Other peptide positions were also affected. Because most of the non-B*27 MHC-I molecules associated with AS risk bind a relatively high percentage of peptides with N-terminal basic residues, we hypothesize that the non-epistatic association of ERAP2 with AS might be related to the processing of peptides with these residues, thus affecting the peptidomes of AS-associated MHC-I molecules.

Association of Genetic Variants of RANK, RANKL, and OPG with Ankylosing Spondylitis Clinical Features in Taiwanese

Ankylosing spondylitis (AS) is a chronic inflammatory disease that leads to spinal ankylosis. The receptor activator of the nuclear factor-kappa (RANK), RANK ligand, and osteoprotegerin (OPG) (RANK/RANKL/OPG) pathway plays critical roles in bone metabolism and the immune system. The current study was aimed at investigating whether six single-nucleotide polymorphisms (SNPs) within the RANK, RANKL, and OPG genes essential for bone homeostasis are associated with AS. Genotype distributions, allele and haplotype frequencies, were compared between 1120 AS patients and 1435 healthy controls and among AS patients with stratification by syndesmophyte formation, onset age, and HLA-B27 positivity. We found that RANKL SNPs were associated with AS syndesmophyte formation. Notably, the RANKL SNP haplotype rs7984870C/rs9533155G/rs9525641C was negatively associated with AS susceptibility and appeared to protect against syndesmophyte formation in AS. Functionally, RANKL promoter SNPs (rs9525641 C/T and rs9533155 G/C) affected DNA-protein complex formation and promoter activity in promoter reporter analyses. The OPG SNP haplotype rs2073618G/rs3102735T was significantly associated with HLA-B27 negativity in AS patients. Furthermore, AS patients with syndesmophyte formation had significantly lower levels of soluble RANKL levels than those without syndesmophyte formation. Our data suggested a role for RANKL in AS susceptibility and severity.

Aqueous Humor Analysis Identifies Higher Branched Chain Amino Acid Metabolism as a Marker for Human Leukocyte Antigen-B27 Acute Anterior Uveitis and Disease Activity

PURPOSE

Human leukocyte antigen-B27 (HLA-B27)-positive acute anterior uveitis (AAU) has a higher recurrence rate and shows more anterior chamber cell infiltration compared with HLA-B27-negative patients, suggesting distinct etiologies of these clinically overlapping conditions. To advance our understanding of the biology of AAU, we characterized the metabolic profile of aqueous humor (AqH) of patients with HLA-B27-associated AAU (B27-AAU) and noninfectious idiopathic AAU (idiopathic AAU).

DESIGN

Experimental laboratory study.

METHODS

AqH samples from 2 independent cohorts totaling 30 patients with B27-AAU, 16 patients with idiopathic AAU, and 20 patients with cataracts underwent 2 individual rounds of direct infusion mass spectrometry. Features predicted by direct infusion mass spectrometry that facilitated maximum separation between the disease groups in regression models were validated by liquid chromatography/tandem mass spectrometry-based quantification with appropriate standards.

RESULTS

Partial least square-discriminant analysis revealed metabolite profiles that were able to separate patients with B27-AAU from those with iodiopathic AAU. Pathway enrichment analysis, based on metabolites on which separation of the groups in the partial least square-discriminant analysis model was based, demonstrated the involvement of branched-chain amino acid biosynthesis, ascorbate and aldarate metabolism, the tricarboxylic acid cycle, and glycolysis-diverting pathways (eg, serine biosynthesis) across all investigated cohorts. Notably, the metabolite ketoleucine was elevated in B27-AAU across all 3 runs and moderately-but robustly-correlated with anterior chamber cell count (correlation coefficient range 0.41-0.81).

CONCLUSIONS

These results illustrate metabolic heterogeneity between HLA-B27-positive and HLA-B27-negative AAU, including an increase of branched-chain amino acid biosynthesis, that reflects disease activity in AAU.

Distinct mechanisms survey the structural integrity of HLA-B*27:05 intracellularly and at the surface

HLA-B*27:05 is associated with the development of autoimmune spondyloarthropathies, but the precise causal relationship between the MHC haplotype and disease pathogenesis is yet to be elucidated. Studies focusing on the structure and cellular trafficking of HLA-B*27:05 implicate several links between the onset of inflammation and the unusual conformations of the molecule inside and at the surface of antigen presenting cells. Several lines of evidence emphasize the emergence of those unnatural protein conformations under conditions where peptide loading onto B*27:05 is impaired. To understand how cellular factors distinguish between poorly loaded molecules from the optimally loaded ones, we have investigated the intracellular transport, folding, and cell surface expression of this particular B27 subtype. Our findings show that B*27:05 is structurally unstable in the absence of peptide, and that an artificially introduced disulfide bond between residues 84 and 139 conferred enhanced conformational stability to the suboptimally loaded molecules. Empty or suboptimally loaded B*27:05 can escape intracellular retention and arrive at the cell surface leading to the appearance of increased number of β₂m-free heavy chains. Our study reveals a general mechanism found in the early secretory pathways of murine and human cells that apply to the quality control of MHC class I molecules, and it highlights the allotype-specific structural features of HLA-B*27:05 that can be associated with aberrant antigen presentation and that might contribute to the etiology of disease.

Stress proteins in the pathogenesis of spondyloarthritis

Spondyloarthritis is an autoinflammatory rheumatic disease in which arthritis and osteoproliferation lead the patients who suffer from it to chronic disability. This disease is associated with the expression of class I MHC molecule HLA-B27, which tends to be misfolded in the endoplasmic reticulum and, therefore, expressed in aberrant forms. This phenomena lead to endoplasmic reticulum stress, which in time, evokes a whole response to cellular injury. Under these conditions, the molecules involved in restoring cell homeostasis play a key role. Such is the case of the "heat-shock proteins", which usually regulate protein folding, but also have important immunomodulatory functions, as well as some roles in tissue modeling. In this review, we attempt to summarize the involvement of cell stress and heat-shock proteins in the homeostatic disturbances and pathological conditions associated with this disease.

The Role of Autophagy in the Degradation of Misfolded HLA-B27 Heavy Chains

OBJECTIVE

To determine whether autophagy is involved in the degradation of misfolded HLA-B27 in experimental spondyloarthritis.

METHODS

Bone marrow-derived macrophages from HLA-B27/human β2 -microglobulin (hβ2 m)-transgenic rats were incubated in the presence or absence of interferon-γ and proteasome or autophagy inhibitors. Immunoprecipitation, immunoblotting, and immunofluorescence analysis were used to measure HLA-B27 heavy chains and autophagy. Autophagy was induced using rapamycin. Macrophages from HLA-B7/hβ2 m-transgenic and wild-type rats were used as controls.

RESULTS

HLA-B27-expressing macrophages showed phosphatidylethanolamine-conjugated microtubule-associated protein 1 light chain 3B levels similar to those in both control groups, before and after manipulation of autophagy. Blocking autophagic flux with bafilomycin resulted in the accumulation of misfolded HLA-B27 dimers and oligomers as well as monomers, which was comparable with the results of blocking endoplasmic reticulum-associated degradation (ERAD) with the proteasome inhibitor bortezomib. HLA-B7 monomers also accumulated after blocking each degradation pathway. The ubiquitin-to-heavy chain ratio was 2-3-fold lower for HLA-B27 than for HLA-B7. Activation of autophagy with rapamycin rapidly eliminated ~50% of misfolded HLA-B27, while folded HLA-B27 or HLA-B7 monomeric heavy chains were minimally affected.

CONCLUSION

This study is the first to demonstrate that both autophagy and ERAD play roles in the elimination of excess HLA class I heavy chains expressed in transgenic rats. We observed no evidence that HLA-B27 expression modulated the autophagy pathway. Our results suggest that impaired ubiquitination of HLA-B27 may play a role in the accumulation of misfolded disulfide-linked dimers, the elimination of which can be enhanced by activation of autophagy. Manipulation of the autophagy pathway should be further investigated as a potential therapeutic target in spondyloarthritis.

Cell-Extrinsic MHC Class I Molecule Engagement Augments Human NK Cell Education Programmed by Cell-Intrinsic MHC Class I

The effector potential of NK cells is counterbalanced by their sensitivity to inhibition by "self" MHC class I molecules in a process called "education." In humans, interactions between inhibitory killer immunoglobulin-like receptors (KIR) and human MHC (HLA) mediate NK cell education. In HLA-B(∗)27:05(+) transgenic mice and in patients undergoing HLA-mismatched hematopoietic cell transplantation (HCT), NK cells derived from human CD34(+) stem cells were educated by HLA from both donor hematopoietic cells and host stromal cells. Furthermore, mature human KIR3DL1(+) NK cells gained reactivity after adoptive transfer to HLA-B(∗)27:05(+) mice or bone marrow chimeric mice where HLA-B(∗)27:05 was restricted to either the hematopoietic or stromal compartment. Silencing of HLA in primary NK cells diminished NK cell reactivity, while acquisition of HLA from neighboring cells increased NK cell reactivity. Altogether, these findings reveal roles for cell-extrinsic HLA in driving NK cell reactivity upward, and cell-intrinsic HLA in maintaining NK cell education.

ERAP1 reduces accumulation of aberrant and disulfide-linked forms of HLA-B27 on the cell surface

OBJECTIVE

Endoplasmic reticulum (ER) aminopeptidase 1 (ERAP1) variants contribute to the risk of ankylosing spondylitis in HLA-B27 positive individuals, implying a disease-related interaction between these gene products. The aim of this study was to determine whether reduced ERAP1 expression would alter the cell surface expression of HLA-B27 and the formation of aberrant disulfide-linked forms that have been implicated in the pathogenesis of spondyloarthritis.

METHODS

ERAP1 expression was knocked down in monocytic U937 cells expressing HLA-B27 and endogenous HLA class I. The effect of ERAP1 knockdown on the accumulation HLA-B alleles (B18, B51, and B27) was assessed using immunoprecipitation, isoelectric focusing, and immunoblotting, as well as flow cytometry with antibodies specific for different forms of HLA-B27. Cell surface expression of aberrant disulfide-linked HLA-B27 dimers was assessed by immunoprecipitation and electrophoresis on non-reducing polyacrylamide gels.

RESULTS

ERAP1 knockdown increased the accumulation of HLA-B27 on the cell surface including disulfide-linked dimers, but had no effect on levels of HLA-B18 or -B51. Antibodies with unique specificity for HLA-B27 confirmed increased cell surface expression of complexes shown previously to contain long peptides. IFN-γ treatment resulted in striking increases in the expression of disulfide-linked HLA-B27 heavy chains, even in cells with normal ERAP1 expression.

CONCLUSIONS

Our results suggest that normal levels of ERAP1 reduce the accumulation of aberrant and disulfide-linked forms of HLA-B27 in monocytes, and thus help to maintain the integrity of cell surface HLA-B27 complexes.

Molecular mechanism of the susceptibility difference between HLA-B*27:02/04/05 and HLA-B*27:06/09 to ankylosing spondylitis: substitution analysis, MD simulation, QSAR modelling, and in vitro assay

The human leukocyte antigen HLA-B27 is directly involved in the disease pathogenesis of ankylosing spondylitis (AS). HLA-B27 has a high degree of genetic polymorphism, with 105 currently known subtypes; the presence of aspartic acid at residue 116 (Asp116) has been found to play an essential role in AS susceptibility. Here, we systematically investigated the molecular mechanism of the susceptibility difference between the AS-associated subtypes HLA-B*27:02/04/05 and AS-unassociated subtypes HLA-B*27:06/09 to AS at sequence, structure, energetic and dynamic levels. In total seven variable residues were identified among the five studied HLA-B27 subtypes, in which Asp116 can be largely stabilized by a spatially vicinal, positively charged His114 through a salt bridge, while five other variable residues seem to have only a marginal effect on AS susceptibility. We also employed a quantitative structure-activity relationship approach to model the statistical correlation between peptide structure and affinity to HLA-B*27:05, a genetic ancestor of all other HLA-B27 subtypes and associated strongly with AS. The built regression predictor was verified rigorously through both internal cross-validation and external blind validation, and was then employed to identify potential HLA-B*27:05 binders from >20,000 cartilage-derived self-peptides. Subsequently, the binding potency of the top five antigenic peptides to HLA-B*27:05 was assayed in vitro using a FACS-based MHC stabilization experiment. Consequently, two (QRVGSDEFK and LRGAGTNEK) out of the five peptides were determined to have high affinity (BL50 = 5.5 and 15.8 nM, respectively) and, as expected, both of them possess positively charged Lys at the C-terminus.

Total hip arthroplasty-related osteogenic osteosarcoma: case report and review of the literature

BACKGROUND

Orthopedic implant-related sarcoma is an exceedingly rare, but a known complication of total hip arthroplasty (THA).

CASE PRESENTATION

The authors describe clinical and radiologic features, histologic appearance, and treatment of osteogenic osteosarcoma located in the proximal femoral diaphysis associated with an unstable femoral prosthesis following THA in a 65-year-old male patient. The patient with HLA-B27 positive ankylosing spondylitis underwent arthroplasty 15 years ago.

CONCLUSIONS

The neoplastic process may be considered as an extraordinary complication of THA and might just be coincidental or the result of some derangement of the healing process in host tissue with no definitely proven hypothesis that the implants or their by-products are carcinogenic. The soluble chemical substances from the implanted prosthetic material are, at least in animals, suspected to play a vital role in the pathogenesis of the neoplastic transformation of the bone tissue. The presented case shall alert orthopedic surgeons to clinical, radiologic, and macroscopic similarities between a malignant tumor and benign lesions caused by wear debris at THA sites. At the examination of plane X-rays of patients with THA loosening, the differential diagnosis should always include osteogenic sarcoma, as well. To our knowledge, there have been only nine cases of THA-related osteogenic osteosarcomas described in the English-language literature.

The quantitative prediction of HLA-B*2705 peptide binding affinities using Support Vector Regression to gain insights into its role for the Spondyloarthropathies

Computational methods are increasingly utilised in many immunoinformatics problems such as the prediction of binding affinity of peptides. The peptides could provide valuable insight into the drug design and development such as vaccines. Moreover, they can be used to diagnose diseases. The presence of human class I MHC allele HLA-B*2705 is one of the strong hypothesis that would lead spondyloarthropathies. In this paper, Support Vector Regression is used in order to predict binding affinity of peptides with the aid of experimentally determined peptide-MHC binding affinities of 222 peptides to HLA-B*2705 to get more insight into this problematic disease. The results yield a high correlation coefficient as much as 0.65 and the SVR-based predictive models can be considered as a useful tool in order to predict the binding affinities for newly discovered peptides.

Sulfasalazine Treatment Suppresses the Formation of HLA-B27 Heavy Chain Homodimer in Patients with Ankylosing Spondylitis

Human leukocytic antigen-B27 heavy chain (HLA-B27 HC) has the tendency to fold slowly, in turn gradually forming a homodimer, (B27-HC)₂ via a disulfide linkage to activate killer cells and T-helper 17 cells and inducing endoplasmic reticulum (ER) stress to trigger the IL-23/IL-17 axis for pro-inflammatory reactions. All these consequences lead to the pathogenesis of ankylosing spondylitis (AS). Sulfasalazine (SSA) is a common medication used for treatment of patients with AS. However, the effects of SSA treatment on (B27-HC)₂ formation and on suppression of IL-23/IL-17 axis of AS patients remain to be determined. In the current study, we examine the (B27-HC)₂ of peripheral blood mononuclear cells (PBMC), the mean grade of sarcoiliitis and lumbar spine Bath Ankylosing Spondylitis Radiology Index (BASRI) scores of 23 AS patients. The results indicated that AS patients without (B27-HC)₂ on PBMC showed the lower levels of mean grade of sarcoiliitis and the lumbar spine BASRI scores. In addition, after treatment with SSA for four months, the levels of (B27-HC)₂ on PBMCs were significantly reduced. Cytokines mRNA levels, including TNFα, IL-17A, IL-17F and IFNγ, were also significantly down-regulated in PBMCs. However, SSA treatment did not affect the levels of IL-23 and IL-23R mRNAs.

Fat Metaplasia on Sacroiliac Joint Magnetic Resonance Imaging at Baseline Is Associated with Spinal Radiographic Progression in Patients with Axial Spondyloarthritis

Objective

To study the relationship between inflammatory and structural lesions in the sacroiliac joints (SIJs) on MRI and spinal progression observed on conventional radiographs in patients with axial spondyloarthritis (axSpA).

Methods

One hundred and ten patients who fulfilled the ASAS axSpA criteria were enrolled. All underwent SIJ MRI at baseline and lumbar spine radiographs at baseline and after 2 years. Inflammatory and structural lesions on SIJ MRI were scored using the SPondyloArthritis Research Consortium of Canada (SPARCC) method. Spinal radiographs were scored using the Stoke AS Spinal Score (SASSS). Multivariate logistic regression analysis was performed to identify predictors of spinal progression.

Results

Among the 110 patients, 25 (23%) showed significant radiographic progression (change of SASSS≥2) over 2 years. There was no change in the SASSS over 2 years according to the type of inflammatory lesion. Patients with fat metaplasia or ankyloses on baseline MRI showed a significantly higher SASSS at 2 years than those without (p<0.001). According to univariate logistic regression analysis, age at diagnosis, HLA-B27 positivity, the presence of fat metaplasia, erosion, and ankyloses on SIJ MRI, increased baseline CRP levels, and the presence of syndesmophytes at baseline were associated with spinal progression over 2 years. Multivariate analysis identified syndesmophytes and severe fat metaplasia on baseline SIJ MRI as predictive of spinal radiographic progression (OR, 14.74 and 5.66, respectively).

Conclusion

Inflammatory lesions in the SIJs on baseline MRI were not associated with spinal radiographic progression. However, fat metaplasia at baseline was significantly associated with spinal progression after 2 years.

Associations of Independent IL2RA Gene Variants with Intermediate Uveitis

Purpose

The genetic background for the concomitance of uveitis and other autoimmune diseases remains elusive. Here the role of two IL2RA gene variants (rs11594656 and rs12722495) was investigated in intermediate uveitis and HLAB27 acute anterior uveitis.

Materials and Methods

One hundred fifty-nine patients with HLAB27 acute anterior uveitis, 85 patients with intermediate uveitis, 138 HLAB27 negative controls and 100 HLAB27 positive controls were recruited for this case-control study. Main outcome measures were genotype distribution and allelic frequencies determined by polymerase chain reaction.

Results

The frequencies of carriers of the minor allele at rs11594656 and rs12722495 were significantly different in patients with intermediate uveitis compared to HLAB27 positive and negative controls combined (p<0.05). For rs12722495 the minor G allele was protective (genotypic OR: 0.29 [0.12-0.69]), and for rs11594656 the minor A allele conferred risk (genotypic OR: 1.59 [1.09-2.32]). No significant differences in genotype distribution were found between patients with HLAB27 acute anterior uveitis and HLAB27 positive or negative control subjects.

Conclusions

We found rs11594656 and rs12722495 to be associated with intermediate uveitis but not with HLAB27 acute anterior uveitis. The genetic heterogeneity found at the IL2RA locus could help explain patterns of concomitance with other autoimmune diseases.

The Leukocyte Immunoglobulin-Like Receptor Family Member LILRB5 Binds to HLA-Class I Heavy Chains

Objective

The leukocyte immunoglobulin-like receptor (LILR) family includes inhibitory and stimulatory members which bind to classical and non-classical HLA-class I. The ligands for many LILR including LILRB5 have not yet been identified.

Methods

We generated C-terminal eGFP and N-terminal FLAG-tagged fusion constructs for monitoring LILR expression. We screened for LILR binding to HLA-class I by tetramer staining of 293T cells transfected with LILRA1, A4, A5 A6 and LILRB2 and LILRB5. We also studied HLA class I tetramer binding to LILRB5 on peripheral monocyte cells. LILRB5 binding to HLA-class I heavy chains was confirmed by co-immunoprecipitation.

Results

HLA-B27 (B27) free heavy chain (FHC) dimer but not other HLA-class I stained LILRB5-transfected 293T cells. B27 dimer binding to LILRB5 was blocked with the class I heavy chain antibody HC10 and anti-LILRB5 antisera. B27 dimers also bound to LILRB5 on peripheral monocytes. HLA-B7 and B27 heavy chains co-immunoprecipitated with LILRB5 in transduced B and rat basophil RBL cell lines.

Conclusions

Our findings show that class I free heavy chains are ligands for LILRB5. The unique binding specificity of LILRB5 for HLA-class I heavy chains probably results from differences in the D1 and D2 immunoglobulin-like binding domains which are distinct from other LILR which bind to β2m-associated HLA-class I.

The Rate of Helicobacter pylori Seropositivity in a Group of Korean Patients with HLA-B27-Associated Acute Anterior Uveitis

Purpose

To investigate an association between Helicobacter pylori seropositivity and HLA-B27-positive acute anterior uveitis (AAU) in Korean patients.

Methods

Retrospective analysis was performed with data from 106 patients previously diagnosed with AAU without clinical evidence of spondyloarthropathy. Serum immunoglobulin G antibodies to H. pylori were measured by enzyme-linked immunosorbent assay, and HLA typing was performed using polymerase chain reaction of DNA amplification. We included 72 non-uveitis patients and 35 age- and sex-matched healthy controls in the study.

Results

Of the 106 patients with AAU, 41 (38.7%) were HLA-B27-positive, and 45 (42.5%) were seropositive for H. pylori. Patients with HLA-B27-positive AAU had a significantly lower prevalence of H. pylori seropositivity compared to those with HLA-B27-negative AAU and healthy controls (24.4% vs. 53.8%, p = 0.003; 24.4% vs. 57.1%, p = 0.004, respectively). In the non-uveitis group, however, HLA-B27-positive patients exhibited similar H. pylori seropositivity prevalence to HLA-B27-negative patients and healthy controls (45.5% vs. 55.7%, p = 0.529; 45.5% vs. 57.1%, p = 0.497, respectively). In multivariate analysis, a low prevalence of H. pylori seropositivity was significantly associated with HLA-B27-positive AAU (odds ratio = 0.340, 95% confidence interval 0.135–0.855, p = 0.022).

Conclusions

Our results suggest an inverse association between H. pylori seropositivity and HLA-B27-positive AAU. Further investigation of this association is needed, given the low prevalence of H. pylori seropositivity observed in patients with HLA-B27-positive AAU.

A coincidence of HLA-B27 negative spondyloarthritis and paravertebral non-Hodgkin's lymphoma--a lesson to be learnt from the past experience

We reported a case of a 71-year-old woman with progressive low back pain and neurologic symptoms of lower extremities, who in the background had the coexistence of spondyloarthritis (SpA) and non Hodgkin's lymphoma of the paravertebral location. This example describes a situation where SpA with minimal sacroiliac joints affection has nevertheless led to the overt axial SpA. This situation included undifferentiated or reactive SpA, as well as unusual disease context, presented with late-life disease onset, older age, female gender and no obvious hereditary predisposition. This combination of comorbid factors could allow environmental and disease-specific factors to accumulate over time and to, by modifying the primary, low-penetrant genetic background, lead to the development of lymphoma. By achieving better understanding of disease pathophysiology dynamic, we will be able to improve our capabilities to navigate biologic therapy in the future, in order to prevent the development of both, overt SpA and lymphoproliferative disease.

ERAP1 in the pathogenesis of ankylosing spondylitis

The endoplasmic reticulum aminopeptidase 1 (ERAP1) performs a major role in antigen processing, trimming N-terminally extended peptides to the final epitope for presentation by major histocompatibility complex class I molecules. Recent genome-wide association studies have identified single nucleotide polymorphisms (SNPs) within ERAP1 as being associated with disease, in particular ankylosing spondylitis (AS). AS is a polygenic chronic inflammatory disease with a strong genetic link to HLA-B27 known for over 40 years. The association of ERAP1 SNPs with AS susceptibility is only observed in HLA-B27-positive individuals, which intersect on the antigen processing pathway. Recent evidence examining the trimming activity of polymorphic ERAP1 highlights its role in generating peptides for loading onto and stabilizing HLA-B27, and the consequent alterations in the interaction of specific NK cell receptors, and the activation of the unfolded protein response as important in the mechanism of disease pathogenesis. Here, we discuss the recent genetic association findings linking ERAP1 SNPs with AS disease susceptibility and the effect of these variants on ERAP1 function, highlighting mechanisms by which AS may arise. The identification of these functional variants of ERAP1 may lead to better stratification of AS patients by providing a diagnostic tool and a potential therapeutic target.

A common minimal motif for the ligands of HLA-B*27 class I molecules

CD8(+) T cells identify and kill infected cells through the specific recognition of short viral antigens bound to human major histocompatibility complex (HLA) class I molecules. The colossal number of polymorphisms in HLA molecules makes it essential to characterize the antigen-presenting properties common to large HLA families or supertypes. In this context, the HLA-B*27 family comprising at least 100 different alleles, some of them widely distributed in the human population, is involved in the cellular immune response against pathogens and also associated to autoimmune spondyloarthritis being thus a relevant target of study. To this end, HLA binding assays performed using nine HLA-B*2705-restricted ligands endogenously processed and presented in virus-infected cells revealed a common minimal peptide motif for efficient binding to the HLA-B*27 family. The motif was independently confirmed using four unrelated peptides. This experimental approach, which could be easily transferred to other HLA class I families and supertypes, has implications for the validation of new bioinformatics tools in the functional clustering of HLA molecules, for the identification of antiviral cytotoxic T lymphocyte responses, and for future vaccine development.

HLA-B27 and human β2-microglobulin affect the gut microbiota of transgenic rats

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.

Abdominal aortitis in HLA-B27+ spondyloarthritis: case report with 5-year follow-up and literature review

OBJECTIVES

Aortic disease is a known complication of HLA-B27-associated spondyloarthritis. We present the case of a 52-year-old HLA-B27-positive woman with aortitis of the abdominal aorta and spondyloarthritis.

METHODS

In addition to the case reported, a literature search (MEDLINE) for articles published between 1946 and September 2013 was performed using combinations of the MEDLINE subject headings keywords "spondylarthritis," "ankylosing spondylitis," "reactive arthritis," "psoriatic arthritis," "aortitis," and "abdominal aorta." Relevant references were retrieved.

RESULTS

CASE REPORT

Our patient presented to the ER in June 2008 with a 3-week history of worsening of severe cramping lower abdominal pain. Her history also included recurrent acute episodes of iritis, which eventually led to enucleation of her left eye despite treatment with corticosteroids. CT of the abdomen showed findings suggesting aortitis of the abdominal aorta. She responded to therapy with prednisone, and follow-up imaging showed eventual resolution of the aortitis. She later went on to be diagnosed with psoriatic arthritis with spondylitis.

REVIEW OF LITERATURE

Six previously reported cases of abdominal aortitis in spondyloarthritis were found. Four of these were reported in patients with ankylosing spondylitis, one in reactive arthritis, and one in psoriatic arthritis. The first case reported was in 1958 and the most recent in 2012.

CONCLUSIONS

Rheumatologists should be aware of the possibility of abdominal aortitis occurring in their patients with SpA and should consider it as part of the differential diagnosis in a SpA patient with unexplained visceral pain or systemic features out of proportion to clinically apparent disease.

Phenotype difference between familial and sporadic ankylosing spondylitis in Korean patients

Clustered occurrences of ankylosing spondylitis (AS) in family have been noticed. We evaluated patients with AS confirmed by the modified New York criteria for familial history of AS (one or more first to third degree relatives). The clinical characteristics and the recurrence risks (number of AS patients/number of familial members) of the familial AS compared to sporadic AS were investigated. Out of a total of 204 AS patients, 38 patients (18.6%) reported that they had a familial history of AS. The recurrence risks in the familial AS patients for first, second and third degree family members were 14.5%, 5.2%, and 4.4% respectively. Erythrocyte sedimentation rate (ESR) (22.6 ± 22.2 vs 35.4 ± 34.4, P=0.029) and C-reactive protein (CRP) (1.24 ± 1.7 vs 2.43 ± 3.3, P=0.003) at diagnosis, body mass index (21.9 ± 2.7 vs 23.7 ± 3.3, P=0.002) and frequency of oligoarthritis (13.2% vs 33.7%, P=0.021) were significantly lower in the familial form. The presence of HLA-B27 (97.4% vs 83.1%, P=0.044) was significantly higher in familial AS. In conclusion, Korean familial AS patients show a lower frequency of oligoarthritis, lower BMI, lower ESR and CRP at diagnosis and higher presence of HLA-B27.

Critical role of endoplasmic reticulum aminopeptidase 1 in determining the length and sequence of peptides bound and presented by HLA-B27

OBJECTIVE

HLA-B27 and endoplasmic reticulum aminopeptidase 1 (ERAP1) are the two strongest genetic factors predisposing to ankylosing spondylitis (AS). A key aminopeptidase in class I major histocompatibility complex presentation, ERAP1 potentially contributes to the pathogenesis of AS by altering HLA-B27 peptide presentation. The aim of this study was to analyze the effects of ERAP1 on the HLA-B27 peptide repertoire and peptide presentation to cytotoxic T lymphocytes (CTLs).

METHODS

ERAP1-silenced and -competent HeLa.B27 and C1R.B27 cells were isotope-labeled, mixed, lysed, and then immunoprecipitated using W6/32 or ME1 antibodies. Peptides bound to HLA-B27 were eluted and analyzed by tandem mass spectrometry. Selected peptides were synthesized and tested for HLA-B27 binding ability. The effect of ERAP1 silencing/mutation on presentation of an immunodominant viral HLA-B27 epitope, KK10, to CTLs was also studied.

RESULTS

In both HeLa.B27 and C1R.B27 cells, the proportion of 9-mer HLA-B27-bound peptides was decreased by ERAP1 silencing, whereas the percentages of longer peptides (11-13 mer) were increased. Surprisingly, following ERAP1 silencing, C-terminally extended peptides were readily identified. These were better able to bind to HLA-B27 than were N-terminally extended peptides lacking an arginine at position 2. In both HeLa.B27 cells and mouse fibroblasts expressing HLA-B27, the absence of ERAP1 reduced peptide recognition by HLA-B27-restricted KK10-specific CTLs following infection with recombinant vaccinia virus or transfection with minigenes expressing KK10 precursors. Presence of an AS-protective variant of ERAP1, K528R, as compared to wild-type ERAP1, reduced the peptide recognition by KK10 CTLs following transfection with extended KK10 minigenes.

CONCLUSION

These results show that ERAP1 directly alters peptide binding and presentation by HLA-B27, thus demonstrating a potential pathogenic mechanism in AS. Inhibition of ERAP1 could potentially be used for treatment of AS and other ERAP1-associated diseases.

Concerted in vitro trimming of viral HLA-B27-restricted ligands by human ERAP1 and ERAP2 aminopeptidases

In the classical human leukocyte antigen (HLA) class I antigen processing and presentation pathway, the antigenic peptides are generated from viral proteins by multiple proteolytic cleavages of the proteasome (and in some cases other cytosolic proteases) and transported to the endoplasmic reticulum (ER) lumen where they are exposed to aminopeptidase activity. In human cells, two different ER-resident enzymes, ERAP1 and ERAP2, can trim the N-terminally extended residues of peptide precursors. In this study, the possible cooperative effect of generating five naturally processed HLA-B27 ligands by both proteases was analyzed. We identified differences in the products obtained with increased detection of natural HLA-B27 ligands by comparing double versus single enzyme digestions by mass spectrometry analysis. These in vitro data suggest that each enzyme can use the degradation products of the other as a substrate for new N-terminal trimming, indicating concerted aminoproteolytic activity of ERAP 1 and ERAP2.

NMR spectroscopy reveals unexpected structural variation at the protein-protein interface in MHC class I molecules

β2-Microglobulin (β2m) is a small, monomorphic protein non-covalently bound to the heavy chain (HC) in polymorphic major histocompatibility complex (MHC) class I molecules. Given the high evolutionary conservation of structural features of β2m in various MHC molecules as shown by X-ray crystallography, β2m is often considered as a mere scaffolding protein. Using nuclear magnetic resonance (NMR) spectroscopy, we investigate here whether β2m residues at the interface to the HC exhibit changes depending on HC polymorphisms and the peptides bound to the complex in solution. First we show that human β2m can effectively be produced in deuterated form using high-cell-density-fermentation and we employ the NMR resonance assignments obtained for triple-labeled β2m bound to the HLA-B*27:09 HC to examine the β2m-HC interface. We then proceed to compare the resonances of β2m in two minimally distinct subtypes, HLA-B*27:09 and HLA-B*27:05, that are differentially associated with the spondyloarthropathy Ankylosing Spondylitis. Each of these subtypes is complexed with four distinct peptides for which structural information is already available. We find that only the resonances at the β2m-HC interface show a variation of their chemical shifts between the different complexes. This indicates the existence of an unexpected plasticity that enables β2m to accommodate changes that depend on HC polymorphism as well as on the bound peptide through subtle structural variations of the protein-protein interface.

Altered regulation of ELAVL1/HuR in HLA-B27-expressing U937 monocytic cells

OBJECTIVE

To investigate the role of HLA-B27 expression in the regulation of RNA binding protein (RBP) Embryonic Lethal Abnormal Vision (ELAV) L1/Human antigen R (HuR) expression in Salmonella-infected or LPS-stimulated human monocytic cells, since HuR is a critical regulator of the post-transcriptional fate of many genes (e.g. TNFα) important in inflammatory response.

METHODS

U937 monocytic cells were stably transfected with pSV2neo resistant vector (mock), wild type HLA-B27, or mutated HLA-B27 with amino acid substitutions in the B pocket. Cells were differentiated, infected with Salmonella enteritidis or stimulated with lipopolysaccharide. The expression levels of HuR protein and cleavage products (CP1 and CP2) were detected by Western blotting and flow cytometry. Specific inhibitors were used to study the role of PKR and p38 in HuR expression and generation of CPs. TNFα and IL-10 secretion after p38 and PKR inhibition were measured by ELISA.

RESULTS

Full length HuR is overexpressed and HuR cleavage is disturbed in U937 monocytic cells expressing HLA-B27 heavy chains (HC). Increased full length HuR expression, disturbed cleavage and reduced dependence on PKR after infection correlate with the expression of glutamic acid 45 in the B pocket that is linked to the misfolding of HLA-B27.

CONCLUSION

Results show that the expression of HLA-B27 HCs modulates the intracellular environment of U937 monocyte/macrophages by altering HuR regulation. This phenomenon is at least partly dependent on the misfolding feature of the B27 molecule. Since HuR is an important regulator of multiple genes involved in inflammatory response observations offer an explanation how HLA-B27 may modulate inflammatory response.

An analysis of 372 patients with anterior uveitis in a large Ibero-American cohort of spondyloarthritis: the RESPONDIA Group

OBJECTIVES

This study analysed the frequency of anterior uveitis (AU) and its correlations in a large cohort of patients with spondyloarthritis (SpA).

METHODS

A common protocol of investigation was prospectively applied to 2012 SpA patients in 85 centres from 10 Ibero-American countries. Clinical and demographic variables and disease indexes were investigated. Categorical variables were compared by χ2 and Fisher's exact test, and continuous variables were compared by ANOVA or Kruskal-Wallis test. A value of p<0.05 was considered significant.

RESULTS

AU was referred by 372 SpA patients (18.5%). AU was statistically associated with inflammatory low back pain (p<0.001), radiographic sacroiliitis (p<0.001), enthesopathies (p=0.004), urethritis/acute diarrhoea (p<0.001), balanitis (p=0.002), hip involvement (p=0.002), HLA-B27 (p=0.003), and higher C-reactive protein (p=0.001), whilst it was negatively associated with the number of painful (p=0.03) and swollen (p=0.005) peripheral joints, psoriatic arthritis (p<0.001), psoriasis (p<0.001), nail involvement (p<0.001), and dactilitis (p=0.062; trend). No association with gender, race, and indices (disease activity, functionality and quality of life) was observed. Logistic regression showed that ankylosing spondylitis (p=0.001) and HLA-B27 (p=0.083; trend) was significantly associated with AU, while extra-articular manifestations (predominantly psoriasis) were negatively associated (p=0.016).

CONCLUSIONS

Anterior uveitis is a frequent extra-articular manifestation in SpA patients, positively associated with axial involvement and HLA-B27 and negatively associated with peripheral involvement and psoriatic arthritis.

Peptide-binding motifs associated with MHC molecules common in Chinese rhesus macaques are analogous to those of human HLA supertypes and include HLA-B27-like alleles

Chinese rhesus macaques are of particular interest in simian immunodeficiency virus/human immunodeficiency virus (SIV/HIV) research as these animals have prolonged kinetics of disease progression to acquired immunodeficiency syndrome (AIDS), compared to their Indian counterparts, suggesting that they may be a better model for HIV. Nevertheless, the specific mechanism(s) accounting for these kinetics remains unclear. The study of major histocompatibility complex (MHC) molecules, including their MHC/peptide-binding motifs, provides valuable information for measuring cellular immune responses and deciphering outcomes of infection and vaccine efficacy. In this study, we have provided detailed characterization of six prevalent Chinese rhesus macaque MHC class I alleles, yielding a combined phenotypic frequency of 29 %. The peptide-binding specificity of two of these alleles, Mamu-A2*01:02 and Mamu-B*010:01, as well as the previously characterized allele Mamu-B*003:01 (and Indian rhesus Mamu-B*003:01), was found to be analogous to that of alleles in the HLA-B27 supertype family. Specific alleles in the HLA-B27 supertype family, including HLA-B*27:05, have been associated with long-term nonprogression to AIDS in humans. All six alleles characterized in the present study were found to have specificities analogous to HLA supertype alleles. These data contribute to the concept that Chinese rhesus macaque MHC immunogenetics is more similar to HLA than their Indian rhesus macaque counterparts and thereby warrants further studies to decipher the role of these alleles in the context of SIV infection.

Ultrasonographic assessment of enthesitis in HLA-B27 positive patients with rheumatoid arthritis, a matched case-only study

Introduction

HLA-B27 has a modifier effect on the phenotype of multiple diseases, both associated and non-associated with it. Among these effects, an increased frequency of clinical enthesitis in patients with Rheumatoid Arthritis (RA) has been reported but never explored again. We aimed to replicate this study with a sensitive and quantitative assessment of enthesitis by using standardized ultrasonography (US).

Methods

The Madrid Sonography Enthesitis Index (MASEI) was applied to the US assessment of 41 HLA-B27 positive and 41 matched HLA-B27 negative patients with longstanding RA. Clinical characteristics including explorations aimed to evaluate spondyloarthrtitis and laboratory tests were also done.

Results

A significant degree of abnormalities in the entheses of the patients with RA were found, but the MASEI values, and each of its components including the Doppler signal, were similar in HLA-B27 positive and negative patients. An increase of the MASEI scores with age was identified. Differences in two clinical features were found: a lower prevalence of rheumatoid factor and a more common story of low back pain in the HLA-B27 positive patients than in the negative. The latter was accompanied by radiographic sacroiliitis in two HLA-B27 positive patients. No other differences were detected.

Conclusion

We have found that HLA-B27 positive patients with RA do not have more enthesitis as assessed with US than the patients lacking this HLA allele. However, HLA-B27 could be shaping the RA phenotype towards RF seronegativity and axial involvement.

Expression of HLA-B27 causes loss of migratory dendritic cells in a rat model of spondylarthritis

OBJECTIVE

In rats transgenic for human HLA-B27 and β(2) -microglobulin (B27-transgenic rats), colitis and peripheral inflammation develop spontaneously. Therefore, B27-transgenic rats provide a model of spondylarthritis. Because inflammation in these rats requires CD4+ T lymphocytes and involves intestinal pathology, we hypothesized that dendritic cells (DCs) that migrate from the intestine and control CD4+ T cell differentiation would be aberrant in B27-transgenic rats.

METHODS

Migrating intestinal lymph DCs were collected via thoracic duct cannulation from B27-transgenic and control (HLA-B7-transgenic or nontransgenic) rats. The phenotypes of these DCs and of mesenteric lymph node DCs were assessed by flow cytometry. The ability of DCs to differentiate from bone marrow precursors in vitro was also assessed.

RESULTS

Lymph DCs showed increased activation and, strikingly, lacked the specific DC population that is important for maintaining tolerance to self-antigens. This population of DCs was also depleted from the mesenteric lymph nodes of B27-transgenic rats. Furthermore, in vitro culture of DCs from bone marrow precursors revealed a defect in the ability of B27-transgenic rats to produce DCs of the migratory phenotype, although the DCs that were generated induced enhanced interleukin-17 (IL-17) production from naive CD4+ T cells.

CONCLUSION

We describe 2 different mechanisms by which HLA-B27 may contribute to inflammatory disease: increased apoptotic death of B27-transgenic DCs that normally function to maintain immunologic tolerance and enhanced IL-17 production from CD4+ T cells stimulated by the surviving B27-transgenic DCs.

[Clinical significance of telomerase activity detection of myeloid element in immune related hematocytopenia]

OBJECTIVE

To observe the telomerase activity (TA) in bone marrow mononuclear cell (BMMNC) at pre-therapy and post-therapy in patients with immune related hematocytopenia and immune related pancytopenia (IRH/IRP) so as to explore the relationship between TA and disease process.

METHODS

TA in BMMNC of 108 IRH/IRP patients was detected with telomeric repeat amplification protocol (TRAP)-PCR-ELISA. The expressions of anti-human immunoglobulin IgG, FcγII receptor (FcγIIR), mannose receptor (MR) and interleukin 17A (IL-17A) located on membrane surface were observed by immunofluorescence (IF). A total of 30 iron deficiency anemia patients were selected as case control.

RESULTS

The TA of 108 IRH/IRP patients were 0.251 ± 0.021. And it increased as compared with the control group of 0.062 ± 0.031 at pre-therapy (P < 0.01). The HLA-B27(+) patients among them was 0.270 ± 0.020 while HLA-B27(-) patients 0.181 ± 0.013 (P < 0.05). And HLA-B27(+)IgG elevated IRP was 0.341 ± 0.016 and HLA-B27(-)IgG elevated 0.183 ± 0.010, the difference of TA was significant between two groups (P < 0.01). IgG antibody positive immature hemocyte could be observed in marrow of IRH/IRP patients, and FcγIIR was expressed highly on those activated macrophage (Mφ) in bone marrow. Both IL-17A and MR were expressed on activated dendritic cells and Mφ in marrow of HLA-B27(+) patients. After the therapy of glucocorticoids associated with cyclosporine A and other drugs, the patient's hemogram recovered and the telomerase in BMMNC were re-devitalized.

CONCLUSIONS

The TA of the BMMNC in marrow of IRH/IRP patients is increased, and it shows a close relation between apoptotic degree of hematopoietic cell and the activation of immunocytes. In IRH/IRP, synchronism and equilibrium exist between BMMNC apoptosis and TA.

[Clinical, radiographic and biologic particularities of ankylosing spondylitis in Tunisian patients according to the presence or the absence of the HLA B27 and its sub-types]

To assess the clinical, radiographic and biologic particularities of ankylosing spondylitis (AS) in Tunisian patients according to HLA B27 and its sub-types statute. This was a case-control study that included 100 patients (85 males/15 females) with AS according to the modified New York criteria. Demographic, clinical, AS specific indexes, radiographic and biologic parameters were determined. HLA-B and B27 subtypes typing of all subjects were performed by PCR-SSP. Patients mean age was 38.4 years +/- 12.6 HLA-B27 was found in 62% of patients. The comparison of B27 positive and B27 negative patients revealed a correlation of B27 with age, male gender, family history of spondylarthropathies, age at disease onset, acute onset of the disease, inaugural spinal involvement, uveitis, bilateral and destructive hip arthritis as well as a high score of mSASSS. The most frequent sub-types of HLA B27 were B*2702 (49.2%) and B*2705 (36.3%). No significant difference of the clinical presentation of the disease or severity factors was found among these patients. This study confirmed the contribution of the HLA B27 to the determination of the clinical presentation of AS. The variability of factors linked to B27 may be explained by the polygenic model of the disease.

HLA-B27 modulates intracellular growth of Salmonella pathogenicity island 2 mutants and production of cytokines in infected monocytic U937 cells

BACKGROUND

Salmonella enterica serovar Enteritidis PT4 KS8822/88 replicates rapidly in HLA-B27-transfected human monocytic U937 cells. In this process, Salmonella pathogenicity island 2 (SPI-2) genes play a crucial role. Our previous study indicated that 118 Salmonella genes, including 8 SPI-2 genes were affected by HLA-B27 antigen during Salmonella infection of U937 cells.

METHODS/PRINCIPAL FINDINGS

To further investigate Salmonella replication in HLA-B27-positive U937 monocytic cells, two SPI-2 genes, ssaS and sscA up-regulated most during Salmonella infection of HLA-B27-transfected U937 cells, were mutated by using one-step gene disruption method. Intracellular survival and replication of the mutants in the U937 cells was compared to that of the wild type strain. Surprisingly, the two mutated strains replicated significantly more than the wild type bacteria in HLA-B27-transfected cells. Secretion of tumor necrosis factor alpha (TNF-α) and interleukin 10 (IL-10) was significantly induced during the infection of HLA-B27-transfected U937 cells with the mutants. The results indicated that the certain SPI-2 genes in wild type bacteria suppress Salmonella intracellular growth and production of cytokines in infected HLA-B27-transfected cells. HLA-B27-associated modulation of Salmonella SPI-2 genes and cytokine production may have importance in the persistent infection of the bacteria and the pathogenesis of reactive arthritis.

CONCLUSIONS

The study provides evidence that certain virulence factors of pathogens can reduce the intracellular growth in the host cells. We suggest that the limiting intracellular growth might be a strategy for persistence of bacteria in host cells, keeping a balance between pathogenic growth and pathogenesis.

Endoplasmic reticulum aminopeptidase 1 (ERAP1) exhibits functionally significant interaction with HLA-B27 and relates to subtype specificity in ankylosing spondylitis

OBJECTIVES

The functional interaction of endoplasmic reticulum aminopeptidase 1 (ERAP1) with human leucocyte antigen (HLA)-B*27 could be important in the pathogenesis of ankylosing spondylitis (AS). AS is associated with B*27:04 and B*27:05, but not with B*27:06 and B*27:09. The authors studied the surface expression of peptide-HLA(pHLA)-B27 complexes and HLA class-I free heavy chains (FHCs) on peripheral blood mononuclear cells of patients with AS with different ERAP1 single nucleotide polymorphisms. The effects of ERAP1 suppression on HLA-B*27 subtypes were tested.

METHODS

Peripheral blood mononuclear cells were collected from Caucasian patients with AS for flow cytometry and were stained for pHLA and FHCs. Genotyping was performed for two ERAP1 single nucleotide polymorphisms (rs27044(C/G) and rs30187(C/T)). C1R cells transfected with different HLA-B27 subtypes (B*27:04, B*27:05, B*27:06 and B*27:09) were subjected to ERAP1 suppression by small interfering RNA and stained using the monoclonal antibody (mAb) MARB4 as well as antibodies for pHLA, FHC, intracellular FHC (IC-FHC). MARB4 has been reported to bind to HLA-B27 with extended peptides.

RESULTS

The authors found variations in FHC expression on the monocytes of patients with AS, depending on different ERAP1 variants. Subsequently, using Hmy2.C1R cells in vitro, the authors show that ERAP1 suppression leads to increased IC-FHC and surface pHLA that react with the monoclonal antibody MARB4. The functional interaction between ERAP1 and HLA-B27 molecules appears to be subtype-specific, since ERAP1 suppression leads to changes only in cells expressing B*27:04 or B*27:05, but not B*27:06 or B*27:09.

CONCLUSIONS

Direct or indirect alterations in the ERAP1-HLA-B27 interaction could be crucial by causing changes in peptide presentation or FHC formation by HLA-B27 molecules, as well as by contributing to differential subtype association in spondyloarthropathies.

Coexisting ankylosing spondylitis and rheumatoid arthritis: a case report with literature review

A 30-year-old female patient with coexisting ankylosing spondylitis and rheumatoid arthritis was diagnosed and treated. The human leukocyte antigen (HLA)-B27 is a predisposing factor of ankylosing spondylitis and HLA-DR4 is a predisposing factor of rheumatoid arthritis. This patient was HLA-B27 and HLA-DR4 positive, and ankylosing spondylitis manifested before rheumatoid arthritis. After disease modifying anti-rheumatic drugs successfully arrested ankylosing spondylitis activity the patient conceived and delivered a healthy baby. One year later, she developed peripheral polyarthritis and was diagnosed with rheumatoid arthritis. We hypothesized that pregnancy may be one of the environmental factors that can activate rheumatoid arthritis, and that disease modifying anti-rheumatic drugs play an important role in keeping the disease under control.

Association of ORAI1 haplotypes with the risk of HLA-B27 positive ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic inflammation of the sacroiliac joints, spine and peripheral joints. The aetiology of ankylosing spondylitis is still unclear. Previous studies have indicated that genetics factors such as human leukocyte antigen HLA-B27 associates to AS susceptibility. We carried out a case-control study to determine whether the genetic polymorphisms of ORAI1 gene, a major component of store-operated calcium channels that involved the regulation of immune system, is a susceptibility factor to AS in a Taiwanese population. We enrolled 361 AS patients fulfilled the modified New York criteria and 379 controls from community. Five tagging single nucleotides polymorphisms (tSNPs) at ORAI1 were selected from the data of Han Chinese population in HapMap project. Clinical statuses of AS were assessed by the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI), and Bath Ankylosing Spondylitis Global Index (BAS-G). Our results indicated that subjects carrying the minor allele homozygote (CC) of the promoter SNP rs12313273 or TT homozygote of the SNP rs7135617 had an increased risk of HLA-B27 positive AS. The minor allele C of 3′UTR SNP rs712853 exerted a protective effect to HLA-B27 positive AS. Furthermore, the rs12313273/rs7135617 pairwise allele analysis found that C-G (OR 1.69, 95% CI 1.27, 2.25; p = 0.0003) and T-T (OR 1.75, 95% CI 1.36, 2.27; p<0.0001) haplotypes had a significantly association with the risk of HLA-B27-positive AS in comparison with the T-G carriers. This is the first study that indicate haplotypes of ORAI1 (rs12313273 and rs7135617) are associated with the risk of HLA-B27 positive AS.

[The recognition of patients with spondyloarthritis. New classification criteria]

Spondyloarthritis (SpA) is an umbrella term for a group of rheumatic diseases characterised by inflammation of the sacroiliac (SI) joints and vertebral column; today, differentiation is made between axial SpA and peripheral SpA. Ankylosing spondylitis (Bechterew's disease) is the most typical form of axial SpA whereby sacroiliitis can be found on X-rays of the SI joints. Axial SpA can, however, also be present without radiographic evidence of sacroiliitis. A range of SpA-related symptoms can also manifest themselves outside the musculoskeletal system, for example, uveitis, psoriasis and inflammatory intestinal diseases. Tumour necrosis factor (TNF)-α inhibitors play an important role in the treatment of SpA. New classification criteria have recently been established in which MRI of the SI joints and the presence of the HLA-B27 tissue antigen are key. Axial and peripheral SpA should be recognized early in order to be able to successfully treat these conditions.

Predicting important residues and interaction pathways in proteins using Gaussian Network Model: binding and stability of HLA proteins

A statistical thermodynamics approach is proposed to determine structurally and functionally important residues in native proteins that are involved in energy exchange with a ligand and other residues along an interaction pathway. The structure-function relationships, ligand binding and allosteric activities of ten structures of HLA Class I proteins of the immune system are studied by the Gaussian Network Model. Five of these models are associated with inflammatory rheumatic disease and the remaining five are properly functioning. In the Gaussian Network Model, the protein structures are modeled as an elastic network where the inter-residue interactions are harmonic. Important residues and the interaction pathways in the proteins are identified by focusing on the largest eigenvalue of the residue interaction matrix. Predicted important residues match those known from previous experimental and clinical work. Graph perturbation is used to determine the response of the important residues along the interaction pathway. Differences in response patterns of the two sets of proteins are identified and their relations to disease are discussed.

We propose a statistical thermodynamics model for determining structurally and functionally important residues in ligand-protein interactions. Our method identifies the path that the protein uses in transferring information from one point to the other. We show that a few energetically active residues are most efficient in energy exchange with the surroundings acting as ‘energy gates’. The remaining important residues that we identify are situated along the interaction path. These are the hub residues. Strong correlations exist between energy gates and hub residues along the interaction path, thus relating to allostery and cooperative binding. We studied the structure-function, ligand binding and allosteric activities of ten models of HLA Class I proteins of the immune system. Five of these models belong to the HLA-B*2705 allele and are strongly associated with a chronic inflammatory rheumatic disease. The remaining five from the HLA-B*2709 allele of the same protein are the corresponding properly functioning ones. We show that differences in the contact maps of the two types lead to significant and consistent changes in the fluctuation profile, making the HLA-B*2705 alleles respond too strongly to perturbation.

Protein expression changes in human monocytic THP-1 cells treated with lipoteichoic acid from Lactobacillus plantarum and Staphylococcus aureus

Lipoteichoic acid (LTA) from Staphylococcus aureus (aLTA) and from Lactobacillus plantarum LTA (pLTA) are both recognized by Toll-like receptor 2 (TLR2), but cause different stimulatory effects on the innate immune and inflammatory responses, and their underlying cellular mechanisms are unknown. In this study, comparative proteome analysis was performed using two-dimensional gel electrophoresis and mass spectrometry on protein extracts from human monocyte THP-1 cells stimulated with either aLTA or pLTA. Differentially expressed proteins might be involved in innate immunity and inflammation. Cells treated with aLTA and with pLTA showed different protein expression profiles. Of 60 identified proteins, 10 were present only in treated cells (8 in aLTA-treated only, and 2 in pLTA-treated only), 1 protein (IMPDH2) was suppressed by pLTA, and 49 were up- or down-regulated more than three-fold by aLTA- or pLTA- stimulation. Several proteins involved in immunity or inflammation, antioxidation, or RNA processing were significantly changed in expression by aLTA- or pLTA-stimulation, including cyclophilin A, HLA-B27, D-dopachrome tautomerase, Mn- SOD, hnRNP-C, PSF and KSRP. These data demonstrated that aLTA and pLTA had different effects on the protein profile of THP-1 cells. Comparison of the proteome alterations will provide candidate biomarkers for further investigation of the immunomodulatory effects of aLTA and pLTA, and the involvement of aLTA in the pathogenesis of Staphylococcus aureus sepsis.

From HLA-B27 to spondyloarthritis: a journey through the ER

Almost four decades of research into the role of human leukocyte antigen-B27 (HLA-B27) in susceptibility to spondyloarthritis has yet to yield a convincing answer. New results from an HLA-B27 transgenic rat model now demonstrate quite convincingly that CD8(+) T cells are not required for the inflammatory phenotype. Discoveries that the HLA-B27 heavy chain has a tendency to misfold during the assembly of class I complexes in the endoplasmic reticulum (ER) and to form aberrant disulfide-linked dimers after transport to the cell surface have forced the generation of new ideas about its role in disease pathogenesis. In transgenic rats, HLA-B27 misfolding generates ER stress and leads to activation of the unfolded protein response, which dramatically enhances the production of interleukin-23 (IL-23) in response to pattern recognition receptor agonists. These findings have led to the discovery of striking T-helper 17 cell activation and expansion in this animal model, consistent with results emerging from humans with spondyloarthritis and the discovery of IL23R as an additional susceptibility gene for ankylosing spondylitis. Together, these results suggest a novel link between HLA-B27 and the T-helper 17 axis through the consequences of protein misfolding and open new avenues of investigation as well as identifying new targets for therapeutic intervention in this group of diseases.

HLA-B27 misfolding and the unfolded protein response augment interleukin-23 production and are associated with Th17 activation in transgenic rats

OBJECTIVE

To determine whether HLA-B27 misfolding and the unfolded protein response (UPR) result in cytokine dysregulation and whether this is associated with Th1 and/or Th17 activation in HLA-B27/human beta(2)-microglobulin (Hubeta(2)m)-transgenic rats, an animal model of spondylarthritis.

METHODS

Cytokine expression in lipopolysaccharide (LPS)-stimulated macrophages was analyzed in the presence and absence of a UPR induced by chemical agents or by HLA-B27 up-regulation. Cytokine expression in colon tissue and in cells purified from the lamina propria was determined by real-time reverse transcription-polymerase chain reaction analysis, and differences in Th1 and Th17 CD4+ T cell populations were quantified after intracellular cytokine staining.

RESULTS

Interleukin-23 (IL-23) was found to be synergistically up-regulated by LPS in macrophages undergoing a UPR induced by pharmacologic agents or by HLA-B27 misfolding. IL-23 was also increased in the colon tissue from B27/Hubeta(2)m-transgenic rats concurrently with the development of intestinal inflammation, and IL-17, a downstream target of IL-23, exhibited robust up-regulation in a similar temporal pattern. IL-23 and IL-17 transcripts were localized to CD11+ antigen-presenting cells and CD4+ T cells, respectively, from the colonic lamina propria. Colitis was associated with a 6-fold expansion of CD4+ IL-17-expressing T cells.

CONCLUSION

The IL-23/IL-17 axis is strongly activated in the colon of B27/Hubeta(2)m-transgenic rats with spondylarthritis-like disease. HLA-B27 misfolding and UPR activation in macrophages can result in enhanced induction of the pro-Th17 cytokine IL-23. These results suggest a possible link between HLA-B27 misfolding and immune dysregulation in this animal model, with implications for human disease.

Clinical features and prognosis of HLA-B27 positive and negative anterior uveitis in a Korean population

Clinical features and prognosis of HLA-B27 positive anterior uveitis (AU) were assessed compared with HLA-B27 negative AU in a Korean population, based on the medical records of AU patients seen at a university hospital. Twenty-seven HLA-B27 negative, idiopathic AU patients (group I) and 55 HLA-B27 positive AU patients (group II) were studied. HLA-B27 positive group was further divided into 29 with associated systemic disease (seronegative spondyloarthropathy) (group IIA) and 26 without associated systemic disease (group IIB). Significantly more severe anterior chamber inflammation in terms of anterior chamber cells (P=0.006) and hypopyon formation (P=0.034) was observed with higher frequency of AU attacks (P=0.007) in the HLA-B27 positive group than in the HLA-B27 negative group. Systemic/periocular steroids were required in significantly more patients in the HLA-B27 positive group than in the HLA-B27 negative group (P=0.015). However, no significant differences were observed for final ocular and visual outcomes between these two groups. Associated systemic disease made no significant difference in the clinical features and prognosis in the HLA-B27 positive AU patients. In conclusion, despite more severe inflammation and a higher recurrence rate, HLA-B27 positive AU shows similar good final ocular and visual outcomes compared to HLA-B27 negative, idiopathic AU in a Korean population.

Immunologic and genetic links between spondylarthropathies and inflammatory bowel diseases

BACKGROUND AND OBJECTIVE

Spondyloarthritis (SpA) is a well recognized extraintestinal manifestation of Inflammatory Bowel Diseases (IBDs), either Crohn's Disease(CD) or Ulcerative Colitis (UC). A much larger percentage of SpA patients have subclinical gut inflammation manifested either by endoscopic findings or by histology. The aim of the present article is to review clinical and experimental evidences regarding the immunological and genetic links between gut and joint inflammation in IBDs and SpA.

EVIDENCE AND INFORMATION SOURCES

A systematic review using PubMed database entering IBD and SpA as key words was performed.

STATE OF THE ART

The association with HLA-B27 is less strong in IBD-associated SpA than in Idiopathic Ankylosing Spondylitis (AS) and there is some evidence for an association between gut inflammation in SpA and CD related CARD15 mutations. A common inflammatory pathogenic pathway has been suggested in gut and joint inflammation in IBD. Treatment of SpA associated with IBD has gained major advances in recent years with the advent of anti-TNF-alpha therapy.

PERSPECTIVES

The adaptive immune response in IBD is thought to be strictly differentiated between Th1 and Th2 in CD and UC respectively. Recent findings, however, suggest that novel effector pathways could drive tissue damage. The most important pathway now emerging is the IL-23/IL-17 axis.

CONCLUSIONS

Present and future advancements of knowledge on mechanisms of inflammation will likely lead to new therapeutic targets.

HLA-B27 rats develop osteopaenia through increased bone resorption without any change in bone formation

Osteopaenia is a common complication of inflammatory bowel diseases (IBD). However, the mechanisms of bone loss are still the subject of debate. The aims of this study were to investigate bone loss in HLA-B27 transgenic rats, a spontaneous model of colitis and to compare the results provided by the usual markers of bone remodelling and by direct measurement of bone protein synthesis. Systemic inflammation was evaluated in HLA-B27 rats and control rats from 18 to 27 months of age. Then bone mineral density, femoral failure load, biochemical markers of bone remodelling and protein synthesis in tibial epiphysis were measured. Bone mineral density was lower in HLA-B27 rats than in controls. Plasma osteocalcin, a marker of bone formation, and fractional protein synthesis rate in tibial epiphysis did not differ between the two groups of rats. In contrast, urinary excretion of deoxypyridinoline, a marker of bone resorption, was significantly increased in HLA-B27 rats. The present results indicate that bone fragility occurs in HLA-B27 rats and mainly results from an increase in bone resorption. Systemic inflammation may be the major cause of the disruption in bone remodelling homeostasis observed in this experimental model of human IBD.