Next-Generation HLA Sequence Analysis Uncovers Shared Risk Alleles Between Clinically Distinct Forms of Childhood Uveitis

Uveitis Associated with Juvenile Idiopathic Arthritis

Juvenile idiopathic arthritis (JIA) is the most common cause of uveitis in children. While symptoms are usually mild, persistent eye inflammation could lead to severe complications and impaired vision. It is essential that JIA patients at risk are diagnosed with uveitis early, receive adequate treatment, and avoid developing complications, such as cataract, glaucoma, and amblyopia. The purpose of this mini-review is to summarize the screening strategies and clinical management for JIA-associated uveitis (JIA-U) as well as the current state of molecular markers linked to this condition. Because glaucoma is one of the most common causes of visual loss in JIA-U, special focus will be put on this serious complication. We conclude by describing the current evidence regarding the long-standing question of whether chronic anterior uveitis without arthritis may be the same disease entity as JIA-U.

Involvement of the systemic microcirculation in pediatric uveitis

BACKGROUND

Pediatric uveitis is a severe inflammatory ocular condition that can lead to sight-threatening complications and can negatively impact quality of life. The retinal microcirculation is often affected in intermediate uveitis and panuveitis. Here, we examined the extraocular (i.e., systemic) microcirculation in pediatric uveitis cases and healthy controls using nailfold capillaroscopy (NFC).

METHODS

We performed NFC in 119 children with noninfectious uveitis and 25 healthy pediatric controls, and assessed the following parameters: capillary density (number of capillaries/mm), dilated capillaries (apex > 20 µm), avascular area, the presence of microhemorrhages, and capillary morphology. Differences in NFC parameters between cases and controls were calculated using regression analysis after adjusting for age and sex.

RESULTS

The mean (± SD) age of the patient group was 13.7 (± 3) years, with 56% females; 46%, 18%, and 36% of cases presented as anterior uveitis, intermediate uveitis, and panuveitis, respectively, with an overall mean disease duration of 4.7 (± 4.0) years. Compared to the control group, the pediatric uveitis cases had a significantly higher number of dilated capillaries/mm and a higher prevalence of ramified capillaries. Moreover, compared to the control group the intermediate uveitis cases had a significantly higher number of dilated capillaries, whereas the anterior uveitis cases had a lower capillary density and a higher prevalence of ramified capillaries.

CONCLUSIONS

Children with uveitis without systemic disease can present with changes in systemic microcirculation. These changes vary amongst the subtypes of uveitis.

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.

HLA Class I Supertype Classification Based on Structural Similarity

HLA class I proteins, a critical component in adaptive immunity, bind and present intracellular Ags to CD8+ T cells. The extreme polymorphism of HLA genes and associated peptide binding specificities leads to challenges in various endeavors, including neoantigen vaccine development, disease association studies, and HLA typing. Supertype classification, defined by clustering functionally similar HLA alleles, has proven helpful in reducing the complexity of distinguishing alleles. However, determining supertypes via experiments is impractical, and current in silico classification methods exhibit limitations in stability and functional relevance. In this study, by incorporating three-dimensional structures we present a method for classifying HLA class I molecules with improved breadth, accuracy, stability, and flexibility. Critical for these advances is our finding that structural similarity highly correlates with peptide binding specificity. The new classification should be broadly useful in peptide-based vaccine development and HLA-disease association studies.

Clinical course and outcome in pediatric idiopathic chronic anterior uveitis

PURPOSE

To examine the clinical course and outcome in children with idiopathic chronic anterior uveitis (iCAU) and compare the results with age-matched children with juvenile idiopathic arthritis-associated uveitis (JIA-U).

DESIGN

Retrospective cohort study.

METHODS

Data regarding ocular complications, visual acuity, and systemic treatment were retrospectively collected for two patient groups that were matched regarding age and year of uveitis diagnosis. Outcome was evaluated using survival analysis.

RESULTS

The iCAU and JIA-U groups included 48 patients with 83 affected eyes and 48 patients with 73 affected eyes, respectively. Multivariate analyses showed that iCAU was associated with a higher prevalence of posterior synechiae (adjusted hazard rate [aHR]: 3.63; P < 0.001) and cataract surgery (aHR: 2.90; P = 0.006). Baseline visual acuity was worse in the iCAU group compared to the JIA-U group (20/25 vs. 20/20, respectively; P < 0.001), but improved in the iCAU group after 5 years (20/20 vs. 20/20, respectively; P = 0.052). At the 5-year follow-up, the younger children with iCAU (≤8 years of age at diagnosis) had a higher prevalence of posterior synechiae (aHR: 2.56; P = 0.007), secondary glaucoma (aHR: 16.0; P = 0.020), and cataract surgery (aHR: 4.79; P = 0.004) compared to older children with iCAU (≥9 years at diagnosis).

CONCLUSIONS

Vision-threatening ocular complications are more common in children with iCAU compared to children with JIA-U, particularly in cases in which the onset of uveitis occurred at ≤8 years of age. However, the long-term vision of these children can be improved with adequate treatment.