Background Ankylosing spondylitis (AS) is strongly associated with HLA-B27. Although AS and HLA-B27 interaction is one of the best known disease associations and has been recognized since 1973 (1, 2), accurate HLA-B27 typing is technically challenging. Previously major histocompatibility complex (MHC) tag single nucleotide polymorphisms (SNPs) rs4349859 and rs13202464 were shown to be able to identify HLA-B27 in European and Asian AS patients. And recently SNP rs116488201 was found to tag HLA-B27 allele in both European and Asian populations (3).
Objectives Therefore the objective of this study was to evaluate the sensitivity and specificity of these SNPs in identifying HLA-B27 allele.
Methods We genotyped three SNPs (rs116488202, rs13202464 and rs4349859) by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The primers were designed using Primer3 algorithm via primer-BLAST interface. PCR products were digested by using BmrI, NlaIII and TaqαI restriction endonuclease enzymes. Some of the samples were also sequenced by using ABI 3130 automated DNA sequencer in order to prevent misleading results. HLA-B27 analysis for patient group was performed by using commercially used SSP-typing kit. SSP-typing results were visualized on 2% agarose gel electrophoresis.
Results In total 207 patients (72% male, mean age 43 ± 11 years and 146 [71%] was HLA-B27 positive) with AS according to the modified New York criteria and 32 healthy controls (78%male, mean age 53 ± 11 years and 2 [6%] was HLA-B27 positive) were included in the study. The effect alleles of SNPs rs116488202 (T) and rs4349859 (A) showed a high specificity (1.000). However sensitivity figures of these SNPs for HLA-B27 were 0.486 and 0.469. The effect allele of SNP rs13202464 (G) has a specificity of 0.967 and a sensitivity of 0.530. We also identified that another SNP (rs141774149) in the neighborhood may complicate the genotyping of rs116488202 by RFLP since polymorphism in rs141774149 and effect allele of rs116488202 cause similar restriction fragments by Bmrl restriction enzymes.
Conclusions Our results suggest that the SNPs which previously reported as strongly tagged to HLA-B27 do not have any advantage over the HLA-B27 typing in Turkish population. Further research is needed to identify SNPs that may have stronger association with HLA-B27 in our population.
Brewerton DA, Hart FD, Nicholls A, Caffrey M, James DC, Sturrock RD. Ankylosing spondylitis and HL-A 27. Lancet. 1973 Apr 28;1(7809):904-7.
Schlosstein L, Terasaki PI, Bluestone R, Pearson CM. High association of an HL-A antigen, W27, with ankylosing spondylitis. N Engl J Med. 1973 Apr 5;288(14):704-6.
Robinson PC, Brown MA. The genetics of ankylosing spondylitis and axial spondyloarthritis. Rheum Dis Clin North Am. 2012 Aug;38(3):539-53.
Disclosure of Interest None Declared