Human leukocyte antigen B polymorphism and association between HLA-B27 and endoplasmic reticulum aminopeptidase 1 rs30187 SNP in patients with ankylosing spondylitis in Bangladesh

Objectives: To determine the association of Human leukocyte antigen B (HLA-B) alleles with ankylosing spondylitis and the allelic association of HLA-B27 with endoplasmic reticulum aminopeptidase 1 (ERAP1) single-nucleotide polymorphism (SNP) rs30187 in patients with ankylosing spondylitis (AS). Methods: We studied 48 consecutively enrolled well-defined AS patients and 48 healthy controls recruited from the outpatient clinic of the rheumatology department of Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, Bangladesh. To genotype HLA- B alleles from peripheral blood DNA, we designed sequence-specific primers for polymerase chain reaction. Sanger's sequencing method was used to detect the ERAP1 rs30187 SNP. The HLA-B allele distributions were compared between cases and controls. To infer an allelic association between HLA-B27 and ERAP1, allele distributions from both loci were compared using cross-tabulations. Chi-squared test or Fisher's exact test was used to quantify the association, and their strength of association was tested by odds ratio (OR) with 95% confidence interval (CI). Results: The frequency of HLA-B27 was found to be higher in AS patients (60.4%) than in healthy controls (8.3%). HLA-B27 allele had an OR of 16.8 (95% CI = 5.2-54.4) for the development of AS. Overall, 4% of AS patients had both HLA-B27 and HLA-B40. No significant association was found between ERAP1 rs30187 SNP and HLA-B27 in patients with AS (OR= 1.7, 95% CI = 0.5-5.6). Conclusions: HLA-B27 was significantly associated with AS in patients in Bangladesh. However, no association between ERAP1 rs30187 SNP and HLA-B27 was observed.