HLA-B51 frequency in Iranian patients with Behçet's disease

Behçet disease, new insights in disease associations and manifestations: a next-generation sequencing study

Behçet disease is a multi-system disease associated with human leukocyte antigen (HLA) class I polymorphism. High-resolution next-generation sequencing (NGS) with haplotype analysis has not been performed previously for this disease. Sixty Egyptian patients diagnosed according to the International Study Group (ISG) criteria for Behçet disease and 160 healthy geographic and ethnic-matched controls were genotyped for HLA class I loci (HLA-A, B, C). For HLA class II loci (DRB1, DRB3/4/5, DQA1, DQB1, DPA1, DPB1), 40 control samples were genotyped. High-resolution HLA genotyping was performed using NGS and the results were analyzed. Clinical manifestations were oral ulcers (100%), genital ulcers (100%), eye (55%) and neurological (28%) and vascular involvement (35%). HLA-B*51:08 [odds ratio (OR) = 19·75, 95% confidence interval (CI) = 6·5-79; P < 0·0001], HLA-B*15:03 (OR = 12·15, 95% CI = 3·7-50·7; P < 0·0001), HLA-C*16:02 (OR = 6·53, 95% CI = 3-14; P < 0·0001), HLA-A*68:02 (OR = 3·14, 95% CI = 1·1-8·9; P < 0·01) were found to be associated with Behçet disease, as were HLA-DRB1*13:01 and HLA-DQB1*06:03 (OR = 3·39, 95% CI = 0·9-18·9; P = 0·04 for both). By contrast, HLA-A*03:01 (OR = 0·13, 95% CI = 0-0·8; P = 0·01) and HLA-DPB1*17:01 were found to be protective (OR = 0·27, 95% CI = 0·06-1·03; P = 0·02). We identified strong linkage disequilibrium between HLA-B*51:08 and C*16:02 and A*02:01 in a haplotype associated with Behçet disease. HLA-B*51:08 was significantly associated with legal blindness (OR = 2·98, 95% CI = 1·06-8·3; P = 0·01). In Egyptian Behçet patients, HLA-B*51:08 is the most common susceptibility allele and holds poor prognosis for eye involvement.

Characterization of the major histocompatibility complex locus association with Behçet's disease in Iran

Introduction

The aim of this study was to characterize the association of human leukocyte antigen (HLA) B alleles and major histocompatibility complex (MHC) single nucleotide polymorphisms (SNPs) with Behçet’s disease (BD) in an Iranian dataset.

Methods

The association of three SNPs in the MHC region previously identified as the most associated in high-density genotyping studies was tested in a case–control study on 973 BD patients and 825 controls from Iran, and the association of HLA-B alleles was tested in a subset of 681 patients and 414 controls.

Results

We found that HLA-B*51 (P = 4.11 × 10⁻⁴¹, OR [95% CI] = 4.63[3.66-5.85]) and B*15 confer risk for BD (P = 2.83 × 10⁻², OR [95% CI] = 1.75[1.08-2.84]) in Iranian, and in B*51 negative individuals, only the B*15 allele is significantly associated with BD (P = 2.51 × 10⁻³, OR [95% CI] = 2.40[1.37-4.20]). rs76546355, formerly known as rs116799036, located between HLA-B and MICA (MHC class I polypeptide-related sequence A), demonstrated the same level of association with BD as HLA-B*51 (P_adj = 1.78 × 10⁻⁴⁶, OR [95% CI] = 5.46[4.21-7.09], and P_adj = 8.34 × 10⁻⁴⁸, OR [95% CI] = 5.44[4.20-7.05], respectively) in the HLA-B allelotyped subset, while rs2848713 was less associated (P_adj = 7.14 × 10⁻³⁵, OR [95% CI] = 3.73[2.97-4.69]) and rs9260997 was not associated (P_adj = 1.00 × 10⁻¹). Additionally, we found that B*51 genotype-phenotype correlations do not survive Bonferroni correction, while carriers of the rs76546355 risk allele predominate in BD cases with genital ulcers, positive pathergy test and positive BD family history (2.31 × 10⁻⁴ ≤ P ≤ 1.59 × 10⁻³).

Conclusions

We found that the HLA-B*51 allele and the rs76546355/rs116799036 MHC SNP are independent genetic risk factors for BD in Iranian, and that positivity for the rs76546355/rs116799036 risk allele, but not for B*51, does correlate with specific demographic characteristics or clinical manifestations in BD patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0585-6) contains supplementary material, which is available to authorized users.

The relationship between plasma homocysteine level and HLA-B51 in patients with Behcet's disease: a case-control study

BACKGROUND

Various coagulation disorders have been reported to explain hypercoagulability state in Behcet's disease (BD). A possible negative association between human leukocyte antigen (HLA)-B51 and increased homocysteine level has been suggested in a previous report from Iranian patients with BD. The aim of this study was to find any possible relationship between plasma homocysteine levels and HLA-B51.

METHODS

In a case-control study, BD patients (fulfilling the new International Criteria for BD) and controls (who had similar clinical symptoms but BD was clinically excluded in them) were included. Mean plasma homocysteine levels measured by enzyme-linked immunosorbent assay in HLA-B51 positive and negative individuals both in patients and controls were compared by t-test, Mann-Whitney test and analysis of variance (F-test).

RESULTS

Ninety-six BD patients and 152 controls were recruited. There was no significant difference between HLA-B51 positive and negative individuals either in the mean plasma homocysteine levels (13.59 ± 9.03 vs. 12.95 ± 4.98 μmol/L, P = 0.514), or in the prevalence of hyperhomocysteinemia (17% vs. 21.4%, P = 0.504). This was true both for BD and control groups. In HLA-B51 positive and negative BD patients, mean plasma homocysteine levels were 14.29 ± 12.02 and 12.62 ± 4.79 μmol/L, respectively (P = 0.33), and the prevalence of hyperhomocysteinemia was 20.8% versus 19.5% (P = 0.55). In the control group, the mean plasma homocysteine levels in HLA-B51 positive and negative individuals were 12.85 ± 4.28 and 13.14 ± 5.10 μmol/L, respectively (P = 0.794), and the prevalence of hyperhomocysteinemia was 13% versus 22.1% (P = 0.23). The difference was non-significant regarding sex (P > 0.71) and disease activity (P > 0.31).

CONCLUSION

In contrast to our previous report, we found no relationship between plasma homocysteine levels and HLA-B51 in this study, either in BD or in the control group.

Behçet's syndrome in Iranian Azari people

Behçet's Syndrome (BS) is a chronic recurrent multisystemic inflammatory disorder characterized by oral and genital ulcers, ocular inflammation. Behçet's syndrome has a complex genetic etiology. However, epidemiological studies recommend that genetic factors have a significant influence to its pathogenesis, alike to other autoinflammatory disorders. Epidemiological statistics, clinical records and HLA typing were studied in Iranian Azari patients with Behçet's syndrome. This investigation considered HLA associations with BS and HLA with certain clinical characteristics, age and sex in the (Tabriz) Iran which has an ethnically homogeneous population. HLA-A and HLA-B typing was performed in 290 BS patients, conforming to International Study Group criteria and in 300 blood donors, as controls. Patient records were retrospectively reviewed and patients reassessed clinically. HLA-B5, HLA-B35, HLA-51, HLA-B52 and HLA-CW4 presented significantly high frequencies in all patients. No other HLA type was associated. There was a significant HLA link with male sex in BS patients and Mean age (34 +/- 1.1) was determined. We present the frequency and correlation between Iranian Azari patients with Behçet's syndrome and particular HLA antigens. Ninety nine percent had mouth ulceration, 64% genital ulceration, 72% skin lesions and 52% ocular involvement. This study supports HLA-B5, HLA-B35, HLA-51, HLA-B52 and HLA-CW4 immunogenetic predisposition in an ethnically homogeneous (Iranian Azari) population.

HLA-B51/B5 and the risk of Behçet's disease: a systematic review and meta-analysis of case-control genetic association studies

OBJECTIVE

To quantify by meta-analysis the genetic effect of the HLA-B5 or HLA-B51 (HLA-B51/B5) allele on the risk of developing Behçet's disease (BD) and to look for potential effect modifiers.

METHODS

Relevant studies were identified using the PubMed Medline database and manual searches of the literature. Pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated by using the random-effects model. Subgroup meta-analyses and meta-regression analyses were undertaken to investigate the effects of selected study-level parameters on the pooled OR. Heterogeneity was assessed using the I2 statistic. Pooled results were used to calculate population-attributable risks (PAR) for BD in relationship to HLA-B51/B5.

RESULTS

A total of 4,800 patients with BD and 16,289 controls from 78 independent studies (published 1975-2007) were selected. The pooled OR of HLA-B51/B5 allele carriers to develop BD compared with noncarriers was 5.78 (95% CI 5.00-6.67), with moderate between-study heterogeneity (I2 = 61%). The subgroup analyses stratifying studies by geographic locations (Eastern Asia, Middle East/North Africa, Southern Europe, Northern/Eastern Europe) yielded consistent OR ranges (5.31-7.20), with I2 ranges of 52-70%. Univariate random-effects meta-regression indicated the percentage of male BD cases (P = 0.008) as a source of heterogeneity. The PAR within the various geographic areas were estimated at 32-52%.

CONCLUSION

The strength of the association between BD and HLA-B51/B5, and its consistency across populations of various ethnicities, lends further support to this allele being a primary and causal risk determinant for BD. Variations according to sex support an interaction of this allele with BD characteristics.