Association of ERAP2 polymorphisms in Colombian HLA-B27+ or HLA-B15+ patients with SpA and its relationship with clinical presentation: axial or peripheral predominance

A study of the association between single nucleotide polymorphisms of the endoplasmic reticulum aminopeptidase 2 (ERAP2) gene and the risk of ankylosing spondylitis in Egyptians

BACKGROUND

Ankylosing spondylitis (AS) is often regarded as the prototypical manifestation of spondylo-arthropathies that prevalently involves the axial skeleton with the potential attribution of ERAP2 polymorphisms to AS predisposition. The purpose of this study was to determine the genetic association between ERAP2 gene rs2910686, and rs2248374 single nucleotide polymorphisms (SNPs) and the risk of ankylosing spondylitis in the Egyptian population.

METHODS AND RESULTS

A cross-sectional work involved 200 individuals: 100 AS individuals diagnosed based on modified New York criteria in 1984 with 100 healthy controls matched in age and gender. The study included a comprehensive evaluation of historical data, clinical examinations, and evaluation of the activity of the disease using the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI). A comprehensive laboratory and radiological evaluation were conducted, accompanied by an assessment and genotyping of the ERAP2 gene variants rs2248374 and rs2910686. This genotyping was performed utilizing a real-time allelic discrimination methodology.Highly statistically substantial variations existed among the AS patients and the healthy control group regarding rs2910686 and rs2248374 alleles. There was a statistically significant difference between rs2910686 and rs2248374 regarding BASDAI, BASFI, mSASSS, ASQoL, V.A.S, E.S.R, and BASMI in the active AS group.

CONCLUSIONS

ERAP2 gene SNPs have been identified as valuable diagnostic biomarkers for AS patients in the Egyptian population being a sensitive and non-invasive approach for AS diagnosis especially rs2910686. Highly statistically significant variations existed among the AS patients and the healthy control group regarding rs2910686 alleles and genotypes.Further research is recommended to explore the potential therapeutic implications of these SNPs.

Human Leukocyte Antigen B*27-Negative Spondyloarthritis: Clinical, Serological, and Radiological Features of a Single-Center Cohort

The strong genetic association between HLA-B*27 and spondyloarthritis (SpA) accounts for about 90% of the susceptibility to axial SpA (axSpA), and the presence of HLA-B*27 is helpful in classifying patients according to the Assessment of SpondyloArthritis International Society (ASAS) classification criteria. However, over the years, other HLA-B alleles have been associated with an increased risk of developing SpA; on this basis, the aim of our study was to describe the demographic, clinical, and radiological characteristics of a cohort of SpA patients who were negative for HLA-B*27. We identified 85 patients with a clinical diagnosis of SpA displaying HLA-B alleles other than HLA-B*27; HLA-B*51 emerged as the most prevalent allele (N = 33, 39%), regardless of the fulfilment of either the axial or the peripheral ASAS criteria. The second most prevalent allele in the full cohort (N = 16, 19%) and in the patients fulfilling either the axial or the peripheral criteria was HLA-B*35. The third most prevalent allele in the full cohort was HLA-B*18 (N = 12, 15%), which was also the second most prevalent allele in the patients fulfilling neither of the two sets of criteria. Overall, the clinical picture was similar across the subgroups fulfilling the different sets of ASAS criteria; however, the patients not fulfilling any ASAS criteria had a higher likelihood of having arthritis compared to the patients fulfilling the axial criteria, whereas the Bath Ankylosing Spondylitis Functional Index was significantly higher in those patients fulfilling the axial criteria compared to those who did not fulfill any criteria. Our results indicate that other HLA alleles, beyond HLA-B*27, could be useful in facilitating SpA diagnosis, particularly in patients with a clinical picture which is consistent with SpA but does not fulfill the ASAS classification criteria.

HLA-B27 may modulate the interaction between ERAP1 polymorphisms and smoking in ankylosing spondylitis patients

BACKGROUND

Ankylosing spondylitis (AS) is an autoimmune disease that affects the enthesis and synovial membrane of the spine, the sacroiliac vertebrae and peripheral joints. Genetic susceptibility to AS is mainly due to the presence of the HLA-B*27 (B27) allele, and endoplasmic reticulum aminopeptidase-1 (ERAP-1) plays a key role in antigen processing and presentation to HLA class I molecules. Tobacco consumption is one of the main environmental factors involved in the pathogenesis of various diseases, including AS. The objective of the present study was to evaluate the association and the interactive effects of variants of the ERAP1 gene with smoking in modulating the risk of AS.

METHODS AND RESULTS

A case-control study in the Mexican population. The association of two functional variants of the ERAP1 gene (rs30187 and rs27044) in patients with AS was analyzed by the allelic discrimination method using TaqMan probes. B27 was typified by PCR-SSP. The interaction between the variants of ERAP1 and B27 and smoking was assessed using the multifactorial dimensionality reduction (MDR) method. There was no significant association of the two variants of ERAP1 in the cases compared with the controls (P > 0.05); however, a strong interaction between the variants and smoking could be demonstrated, with entropy values of 4.97% for rs30187 and 5.13% for rs27044. In addition, these interaction effects were increased in patients carrying the B27 allele.

CONCLUSIONS

The rs30187 and rs27044 variants of the ERAP1 gene appear to potentiate the effect of smoking in patients with AS carrying the B27 allele.

Searching for New Genetic Biomarkers of Axial Spondyloarthritis

Background: Axial spondyloarthritis (axSpA) is a chronic inflammatory condition of the spine. In addition to musculoskeletal symptoms, there are also extra-articular manifestations. The aim of this study was to search for new biomarkers associated with the clinical presentation and treatment response in axSpA patients. Methods: In this study, 106 axSpA patients and 110 healthy controls were enrolled. Six single-nucleotide polymorphisms (SNPs) were selected for genotyping: ERAP1 rs2287987, ERAP2 rs2549782, TNF rs1800629, TNFRSF1A rs767455, TNFRSF1B rs1061622, and FCGR2A rs1801274. Participants were examined at baseline and after 12 and 24 weeks of anti-TNF therapy. Results: SNPs associated with high axSpA initial activity were TNFRSF1A rs767455 and TNFRSF1B rs1061622 (p < 0.008). The ERAP1 rs2287987 AA genotype was more frequently observed in patients with enthesitis (AA vs. G+, p = 0.049), while the TNFRSF1B rs1061622 GG genotype was more common in participants with uveitis (GG vs. TT, p = 0.042). Potential in predicting anti-TNF treatment response was demonstrated by ERAP1 rs2287987, ERAP2 rs2549782, TNFRSF1B rs1061622, and FCGR2A rs1801274. Conclusions: SNPs can be used to identify patients at risk of severe disease to initiate treatment earlier. Genetic testing will allow clinicians to choose the right drug for the patient.

Inflammatory Foot Involvement in Spondyloarthritis: From Tarsitis to Ankylosing Tarsitis

Spondyloarthritis (SpA) is a group that includes a wide spectrum of clinically similar diseases manifested by oligoarticular arthritis and axial or peripheral ankylosis. Although axial SpA is predominant in Caucasians and adult-onset patients, juvenile-onset and Latin American patients are characterized by severe peripheral arthritis and particularly foot involvement. The peripheral involvement of SpA can vary from tarsal arthritis to the most severe form named ankylosing tarsitis (AT). Although the cause and etiopathogenesis of axSpA are often studied, the specific characteristics of pSpA are unknown. Several animal models of SpA develop initial tarsitis and foot ankylosis as the main signs, emphasizing the role of foot inflammation in the overall SpA spectrum. In this review, we attempt to highlight the clinical characteristics of foot involvement in SpA and update the knowledge regarding its pathogenesis, focusing on animal models and the role of mechanical forces in inflammation.

Aberrant antigen processing and presentation: Key pathogenic factors leading to immune activation in Ankylosing spondylitis

The strong association of HLA-B*27 with ankylosing spondylitis (AS) was first reported nearly 50 years ago. However, the mechanistic link between HLA-B*27 and AS has remained an enigma. While 85-90% of AS patients possess HLA-B*27, majority of HLA-B*27 healthy individuals do not develop AS. This suggests that additional genes and genetic regions interplay with HLA-B*27 to cause AS. Previous genome-wide association studies (GWAS) identified key genes that are distinctively expressed in AS, including the Endoplasmic Reticulum Aminopeptidase (ERAP) 1 and ERAP2. As these gene-encoding molecules are primarily implicated in the process of peptide processing and presentation, potential pathological interaction of these molecules with HLA-B*27 may operate to cause AS by activating downstream immune responses. The aberrant peptide processing also gives rise to the accumulation of unstable protein complex in endoplasmic reticulum (ER), which drives endoplasmic reticulum-associated protein degradation (ERAD) and unfolded protein response (UPR) and activates autophagy. In this review, we describe the current hypotheses of AS pathogenesis, focusing on antigen processing and presentation operated by HLA-B*27 and associated molecules that may contribute to the disease initiation and progression of AS.