Searching for New Genetic Biomarkers of Axial Spondyloarthritis

Defining a genetic background for bamboo spine and axial spondyloarthritis

OBJECTIVE

Bamboo spine is the most severe complication of axial spondyloarthritis (AxSpA). This study aims to address whether haplotypes of endoplasmic reticulum aminopeptidase (ERAP)1 and ERAP2 single nucleotide polymorphisms (SNPs), previously associated with AxSpA, are associated with the development of bamboo spine in an AxSpA cohort.

METHODS

The study included 192 patients with AxSpA followed in MARS (MARmara Spondyloarthritis) clinic and fulfilling the modified New York criteria. ERAP1 and ERAP2 polymorphisms were determined by real-time PCR on genomic DNA using the TaqMan SNP Genotyping Assay for SNPs rs72773968, rs3734016, rs26653, rs26618, rs27895, rs2287987, rs30187, rs10050860, rs17482078, rs27044, rs2549782, rs2248374. The HLA-B genotypes were assessed using the LABTypeTM SSO method.

RESULTS

Male gender (P<0.001) and HLA-B27 positivity (P<0.05) were associated with an increased risk of developing a bamboo spine, and peripheral arthritis was significantly less prevalent in AxSpA patients with a bamboo spine (P<0.05). Of the ten ERAP1 haplotypes, haplotype 3 was significantly more prevalent in AxSpA patients with bamboo spine adjusted for HLA-B27 status (P<0.05). Haplotype 3 and -6 were significantly more prevalent exclusively in HLA-B27 (+) patients (P<0.05). Allele frequencies and genotype distributions of single ERAP1 SNPs alone were not significantly different between AxSpA patients with and without bamboo spines. There was no association between bamboo spine development and ERAP2 SNPs.

CONCLUSIONS

Our results indicate that HLA-B27 positivity, ERAP1 haplotype 3 and -6, and being male confer a significant risk for developing bamboo spine. Whether the association of haplotype 3 and -6 with bamboo spine is confined only to our Turkish patient cohort may deserve attention in other ethnicities.

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.

Sex Bias in Diagnostic Delay: Are Axial Spondyloarthritis and Ankylosing Spondylitis Still Phantom Diseases in Women? A Systematic Review and Meta-Analysis

Diagnostic delay (DD) is associated with poor radiological and quality of life outcomes in axial spondyloarthritis (ax-SpA) and ankylosing spondylitis (AS). The female (F) population is often misdiagnosed, as classification criteria were previously studied mostly in males (M). We conducted a systematic review to investigate (i) the difference in DD between the sexes, the impact of HLA*B27 and clinical and social factors (work and education) on this gap, and (ii) the possible influence of the year of publication (before and after the 2009 ASAS classification criteria), geographical region (Europe and Israel vs. extra-European countries), sample sources (mono-center vs. multi-center studies), and world bank (WB) economic class on DD in both sexes. We searched, in PubMed and Embase, studies that reported the mean or median DD or the statistical difference in DD between sexes, adding a manual search. Starting from 399 publications, we selected 26 studies (17 from PubMed and Embase, 9 from manual search) that were successively evaluated with the modified Newcastle-Ottawa Scale (m-NOS). The mean DD of 16 high-quality (m-NOS > 4/8) studies, pooled with random-effects meta-analysis, produces results higher in F (1.48, 95% CI 0.83-2.14, p < 0.0001) but with significant results at the second analysis only in articles published before the 2009 ASAS classification criteria (0.95, 95% CI 0.05-1.85, p < 0.0001) and in extra-European countries (3.16, 95% CI 2.11-4.22, p < 0.05). With limited evidence, some studies suggest that DD in F might be positively influenced by HLA*B27 positivity, peripheral involvement, and social factors.

Shedding Light on the Role of ERAP1 in Axial Spondyloarthritis

Spondyloarthritis (SpA) is a multifactorial chronic inflammatory disease affecting the axial skeleton (axSpA) and/or peripheral joints (p-SpA) and entheses. The disease's pathogenesis depends on genetic, immunological, mechanical, and environmental factors. Endoplasmic reticulum aminopeptidase 1 (ERAP1) is a multifunctional enzyme that shapes the peptide repertoire presented by major histocompatibility complex (MHC) class I molecules. Genome-wide association studies (GWAS) have identified different single nucleotide polymorphisms (SNPs) in ERAP1 that are associated with several autoimmune diseases, including axSpA. Therefore, a deeper understanding of the ERAP1 role in axSpA could make it a potential therapeutic target for this disease and offer greater insight into its impact on the immune system. Here, we review the biological functions and structure of ERAP1, discuss ERAP1 polymorphisms and their association with axSpA, highlight the interaction between ERAP1 and human leukocyte antigen (HLA)-B27, and review the association between ERAP1 SNPs and axSpA clinical parameters.