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

Novel genetic variants of HLA gene associated with Thai Behcet's disease (BD) patients using next generation sequencing technology

Behçet's disease (BD) manifests as an autoimmune disorder featuring recurrent ulcers and multi-organ involvement, influenced by genetic factors associated with both HLA and non-HLA genes, including TNF-α and ERAP1. The study investigated the susceptible alleles of both Class I and II molecules of the HLA gene in 56 Thai BD patients and 192 healthy controls through next-generation sequencing using a PacBio kit. The study assessed 56 BD patients, primarily females (58.9%), revealing diverse manifestations including ocular (41.1%), vascular (35.7%), skin (55.4%), CNS (5.4%), and GI system (10.7%) involvement. This study found associations between BD and HLA-A*26:01:01 (OR 3.285, 95% CI 1.135-9.504, P-value 0.028), HLA-B*39:01:01 (OR 6.176, 95% CI 1.428-26.712, P-value 0.015), HLA-B*51:01:01 (OR 3.033, 95% CI 1.135-8.103, P-value 0.027), HLA-B*51:01:02 (OR 6.176, 95% CI 1.428-26.712, P-value 0.015), HLA-C*14:02:01 (OR 3.485, 95% CI 1.339-9.065, P-value 0.01), HLA-DRB1*14:54:01 (OR 1.924, 95% CI 1.051-3.522, P-value 0.034), and HLA-DQB1*05:03:01 (OR 3.00, 95% CI 1.323-6.798, P-value 0.008). However, after Bonferroni correction none of these alleles were found to be associated with BD. In haplotype analysis, we found a strong linkage disequilibrium in HLA-B*51:01:01, HLA-C*14:02:01 (P-value 0.0, Pc-value 0.02). Regarding the phenotype, a significant association was found between HLA-DRB1*14:54:01 (OR 11.67, 95% CI 2.86-47.57, P-value 0.001) and BD with ocular involvement, apart from this, no distinct phenotype-HLA association was documented. In summary, our study identifies specific HLA associations in BD. Although limited by a small sample size, we acknowledge the need for further investigation into HLA relationships with CNS, GI, and neurological phenotypes in the Thai population.

Exceptional diversity of KIR and HLA class I in Egypt

Genetically determined variation of killer cell immunoglobulin like receptors (KIR) and their HLA class I ligands affects multiple aspects of human health. Their extreme diversity is generated through complex interplay of natural selection for pathogen resistance and reproductive health, combined with demographic structure and dispersal. Despite significant importance to multiple health conditions of differential effect across populations, the nature and extent of immunogenetic diversity is under-studied for many geographic regions. Here, we describe the first high-resolution analysis of KIR and HLA class I combinatorial diversity in Northern Africa. Analysis of 125 healthy unrelated individuals from Cairo in Egypt yielded 186 KIR alleles arranged in 146 distinct centromeric and 79 distinct telomeric haplotypes. The most frequent haplotypes observed were KIR-A, encoding two inhibitory receptors specific for HLA-C, two that are specific for HLA-A and -B, and no activating receptors. Together with 141 alleles of HLA class I, 75 of which encode a KIR ligand, we identified a mean of six distinct interacting pairs of inhibitory KIR and HLA allotypes per individual. We additionally characterize 16 KIR alleles newly identified in the study population. Our findings place Egyptians as one of the most highly diverse populations worldwide, with important implications for transplant matching and studies of immune-mediated diseases.

HLA Alleles in a Behçet Disease Multiethnic Population With and Without Ophthalmic Manifestations

OBJECTIVE

The aim of this study was to analyze HLA alleles in patients with Behçet disease (BD) and their correlation with ophthalmic manifestations (OMs) in a multiethnic Brazilian population.

METHODS

This case-control study compared 72 BD patients with or without OM who underwent a thorough ophthalmologic evaluation, including best-corrected visual acuity, bino-ophthalmoscopy, and HLA analysis, with 144 matched healthy controls. Fluorescein angiography was also performed in the patients with BD and OM. HLA class I (A, B, and C) and II (DRB1, DQB1, and DQA1) typing were performed using PCR-SSO.

RESULTS

Of 72 patients with BD, 42 (58%) had OM. The HLA-B*51 and -A*26 alleles were more frequent in patients with BD than in controls (23.6% vs 14.6% and 12.5% vs 4.3%, respectively), but could not differentiate OM risk. The HLA alleles of BD patients that differentiated those with and without OM were HLA-B*15 (40.5% vs 20.7%; odds ratio [OR], 2.59; p = 0.0059), HLA-C*02 (33.3% vs 13.4%; OR, 3.20; p = 0.0024), and HLA-DQB1*03 (64.3% vs 45.7%, p = 0.017), whereas HLA-A*03 (0.0% vs 13.3%, p = 0.006) and HLA-DRB1*15 (4.8% vs 19.5%; OR, 0.21; p = 0.0121) were protective against OM.

CONCLUSIONS

In this study of a Brazilian multiethnic BD population, alleles were similar between groups of BD patients with and without OM. We described HLA-B*15, -C*02, and -DQB1*03 as risk factors and -A*03 and -DRB1*15 as protective factors for OM in BD, which could function as biomarkers for predicting disease phenotypes.

Associations between HLA class II alleles and IgE sensitization to allergens in the Qatar Biobank cohort

Background

Allergic disorders are the consequence of IgE sensitization to allergens. Population studies have shown that certain human leukocyte antigen (HLA) alleles are associated with increased or decreased risk of developing allergy.

Objective

We aimed to characterize the relationship between HLA class II allelic diversity and IgE sensitization in an understudied Arab population.

Methods

We explored associations between IgE sensitization to 7 allergen mixes and mesquite (comprising 41 food or aeroallergens) and 45 common classical HLA class II alleles in a well-defined cohort of 797 individuals representing the general adult population of Qatari nationals and long-term residents. To do so, we performed HLA calling from whole genome sequencing data at 2-field resolution using 2 independent algorithms. We then applied 3 different regression models to assess either each allergen mix independently, in the context of IgE sensitization to other allergens tested, or polysensitization.

Results

More than half (n = 447) of the study participants showed IgE sensitization to at least 1 allergen, most of them (n = 400) to aeroallergens (Phadiatop). We identified statistically significant negative and positive associations with 24 HLA class II alleles. These have been reported to confer risk or protection from variety of diseases; however, only a few have previously been associated with allergy in other populations.

Conclusions

Our study reveals several new risk and protective genetic markers for allergen-specific IgE sensitization. This is a first and essential step toward a better understanding of the origins of allergic diseases in this understudied population.