HLA class II alleles in Norwegian patients with coexisting type 1 diabetes and celiac disease

High-resolution genotyping of HLA class I loci in children with type 1 diabetes and celiac disease

OBJECTIVES

HLA-DQ2 and DQ8 contribute to the strongest risk haplotypes for type 1 diabetes (T1D) and celiac disease (CD). The variation in genetic risk association is likely linked to different HLA class II loci susceptibility, but association studies of HLA class I alleles are scarce. The aim was to investigate HLA class I A, B, and C alleles polymorphisms in children with only T1D, CD, and a subgroup with both T1D and CD (T1D w/CD).

MATERIALS AND METHODS

HLA class I A, B, and C genes were genotyped using next-generation targeted sequencing. A conditional analysis was performed on 68 children with T1D, 219 children with CD and seven children with T1D w/CD enrolled from a birth cohort study at high genetic risk children from the South of Sweden.

RESULTS

Among 1764 HLA class I allele variants, A*29:02:01 in T1D w/CD was associated with both T1D (OR = 21.42 [1.05, 1322.4], p = 0.0231) and CD (OR = 35 [2.36, 529.12], p = 0.0051) along with C*05:01:01 with both T1D (OR = 5.54 [1.06, 24.8], p = 0.02) and CD (OR = 6.84 [1.46, 26.01], p = 0.0077). No independent effects of HLA-B allele associations were observed in T1D w/CD.

CONCLUSION

Although the distribution of HLA class I alleles differs between children with T1D and CD, the A*29:02:01 and C*05:01:01 alleles showed shared risk association of both diseases.

HLA class II genes in precision-based care of childhood diseases: what we can learn from celiac disease

Celiac disease (CeD) is a chronic immuno-mediated enteropathy caused by dietary gluten with marked autoimmunity traits. The human leukocyte antigen (HLA) class II heterodimers represent the main predisposing factor, although environmental agents, as viral infection, gut microbiota, and dietary regimen, also contribute to CeD risk. These molecules are involved in autoimmunity as they present self-antigens to autoreactive T cells that have escaped the thymic negative selection. In CeD, the HLA class II risk alleles, DQA1*05-DQB1*02 and DQA1*03-DQB1*03, encode for DQ2.5 and DQ8 heterodimers, and, furthermore, disease susceptibility was found strictly dependent on the dose of these genes. This finding questioned how the expression of HLA-DQ risk genes, and of relative surface protein on antigen-presenting cells, might be relevant for the magnitude of anti-gluten inflammatory response in CeD patients, and impact the natural history of disease, its pathomechanisms, and compliance to dietary treatment. In this scenario, new personalized medical approaches will be desirable to support an early, accurate, and non-invasive diagnosis, and to define genotype-guided preventive and therapeutic strategies for CeD. To reach this goal, a stratification of genetic risk, disease outcome, and therapy compliance based on HLA genotypes, DQ2.5/DQ8 expression measurement and magnitude of T cell response to gluten is mandatory. IMPACT: This article revises the current knowledge on how different HLA haplotypes, carrying the DQ2.5/DQ8 risk alleles, impact the onset of CeD. This review discusses how the expression of susceptibility HLA-DQ genes can determine the risk assessment, outcome, and prevention of CeD. The recent insights on the environmental factors contributing to CeD in childhood are reviewed. This review discusses the use of HLA risk gene expression as a tool to support medical precision approaches for an early and non-invasive diagnosis of CeD, and to define genotype-guided preventive and therapeutic strategies.

High-resolution genotyping indicates that children with type 1 diabetes and celiac disease share three HLA class II loci in DRB3, DRB4 and DRB5 genes

Type 1 diabetes (T1D) and celiac disease (CD) share common genetic loci, mainly within the human leukocyte antigen (HLA) class II complex. Extended genotyping of HLA class II alleles and their potential risk for developing both diseases remains to be studied. The present study compared extended HLA-class II gene polymorphisms in children with T1D, CD, and a subgroup diagnosed with both diseases (T1D w/CD). Next-generation targeted sequencing (NGTS) of HLA-DRB3, DRB4, DRB5, DRB1, DQA1, DQB1, DPA1, and DPB1 alleles from DNA collected from 68 T1D, 219 CD, and seven T1D w/CD patients were compared with 636 HLA-genotyped Swedish children from the general population selected as controls. In comparison to controls, the DRB4*01:03:01 allele occurred more frequently in T1D w/CD (odds ratio (OR) = 7.84; 95% confidence interval (95% CI) = (2.24, 34.5), P = 0.0002) and T1D (OR = 3.86; 95% CI, (2.69, 5.55), P = 1.07 × 10^-14 ), respectively. The DRB3*01:01:02 allele occurred more frequently in CD as compared to controls (OR = 7.87; 95% CI, (6.17, 10.03), P = 4.24 × 10^-71 ), but less frequently in T1D (OR = 2.59; 95% CI, (1.76, 3.81), P = 7.29 × 10^-07 ) and T1D w/CD (OR = 0.87; 95% CI, (0.09, 3.96), P ≤ 0.999). The frequency of the DRB4*01:03:01-DRB1*04:01:01-DQA1*03:01:01-DQB1*03:02:01 (DR4-DQ8) haplotype was higher in T1D w/CD (OR = 12.88; 95% CI (4.35, 38.14) P = 3.75 × 10^-9 ), and moderately higher in T1D (OR = 2.13; 95% CI (1.18, 3.83) P = 0.01) compared with controls, but comparable in CD (OR = 1.45; 95% CI (0.94, 2.21), P = 0.08) and controls. Children with T1D and CD are associated with DRB4*01:03:01, DRB3*01:01:02, and DRB3*02:02:01 of which DRB4*01:03:01 confers the strongest risk allele for developing T1D w/CD.

Distribution of HLA-DQ risk genotypes for celiac disease in Ethiopian children

Most patients with celiac disease are positive for either HLA‐DQA1*05:01‐DQB1*02 (DQ2.5) or DQA1*03:01‐DQB1*03:02 (DQ8). Remaining few patients are usually DQA1*02:01‐DQB1*02 (DQ2.2) carriers. Screenings of populations with high frequencies of these HLA‐DQA1‐DQB1 haplotypes report a 1% to 3% celiac disease prevalence. The aim was to determine the prevalence of HLA‐DQ risk haplotypes for celiac disease in Ethiopian children. Dried blood spots collected from 1193 children from the Oromia regional state of Ethiopia were genotyped for HLA‐DQA1 and DQB1 genotyping using an asymmetric polymerase chain reaction (PCR) and a subsequent hybridization of allele‐specific probes. As references, 2000 previously HLA‐genotyped children randomly selected from the general population in Sweden were included. DQ2.2 was the most common haplotype and found in 15.3% of Ethiopian children, which was higher compared with 6.7% of Swedish references (P < .0001). Opposed to this finding, DQ2.5 and DQ8 occurred in 9.7% and 6.8% of Ethiopian children, which were less frequent compared with 12.8% and 13.1% of Swedish references, respectively (P < .0001). The DQ2.5‐trans genotype encoded by DQA1*05‐DQB1*03:01 in combination with DQ2.2 occurred in 3.6% of Ethiopian children, which was higher compared with 1.3% of Swedish references (P < .0001). However, when children with moderate high to very high‐risk HLA genotypes were grouped together, there was no difference between Ethiopian children and Swedish references (27.4% vs 29.0%) (P = .3504). The frequency of HLA risk haplotypes for celiac disease is very similar in Ethiopian and Swedish children. This finding of importance will be useful in future screening of children for celiac disease in Ethiopia.

Carrier frequency of HLA-DQB1*02 allele in patients affected with celiac disease: A systematic review assessing the potential rationale of a targeted allelic genotyping as a first-line screening

BACKGROUND

Celiac Disease (CD) is an immune-mediated disorder, in which the HLA immunogenetic background (DQ2 and DQ8 heterodimers) and environmental trigger (gluten) are well established. Indeed, both factors are necessary – but not sufficient – to develop CD. However, it is very likely that CD is underdiagnosed in both developing and developed countries, due to several aspects, including the fact that a lot of patients present mild and/or atypical symptoms, without the presence of any recognized risk factors. Therefore, the possibility and feasibility of widened screening strategies to identify CD patients are debated.

AIM

To provide further evidence of the main epidemiological importance of HLA-DQB1*02 allele in the population of CD patients.

METHODS

We performed a systematic search in PubMed, EMBASE, Cochrane, Web of Science and Scopus databases, in order to produce a systematic review assessing the carrier frequency of HLA-DQB1*02 allele in the celiac population. Following the PRISMA guidelines, we retrieved all the original articles describing CD patients’ HLA-DQB1 genotype in such a way that could allow to assess the HLA-DQB1*02 carrier frequency among CD patients, along with the evidence of the appropriate diagnostic work-up to achieve a correct and final diagnosis of CD.

RESULTS

The final output of this systematic search in the medical literature consisted of 38 studies providing the appropriate HLA-DQB1 genotype information of the respective CD population. According to this systematic review, including a pool of 4945 HLA-DQ genotyped CD patients, the HLA-DQB1*02 carrier frequency was 94.94%, meaning that only 5.06% of CD patients were completely lacking this allelic variant. Interestingly, if we consider only the studies whereby the prevalence of CD patients affected with type 1 diabetes mellitus was supposed or clearly established to be very low, the frequency of non-HLA-DQB1*02 carriers among CD patients dropped to 3.65%.

CONCLUSION

Such a high carrier frequency of the HLA-DQB1*02 allelic variant (which is > 95%-96% in CD patients without risk factors, like type 1 diabetes mellitus comorbidity) might be exploited to consider a cost-effective and widened screening approach. If a sustainable strategy could be implemented through a low-cost targeted genetic test to detect the individual presence of HLA-DQB1*02 allele, an appropriate algorithm for serological screening in individuals resulting to be genetically predisposed to CD, might be considered.

Role of Dietary Gluten in Development of Celiac Disease and Type I Diabetes: Management Beyond Gluten-Free Diet

Gluten triggers Celiac Disease (CD) and type I diabetes in genetically predisposed population of human leukocyte antigen DQ2/DQ8+ and associates with disorders such as schizophrenia and autism. Application of a strict gluten-free diet is the only well-established treatment for patients with CD, whereas the treatment for patients with celiac type I diabetes may be depend on the timing and frequency of the diet. The application of a gluten-free diet in patients with CD may contribute to the development of metabolic syndrome and nonalcoholic fatty liver disease and may also lead to a high glycemic index, low fiber diet and micronutrient deficiencies. The alteration of copper bioavailability (deficient, excess or aberrant coordination) may contribute to the onset and progress of related pathologies. Therefore, nutrient intake of patients on a gluten-free diet should be the focus of future researches. Other gluten-based therapies have been rising with interest such as enzymatic pretreatment of gluten, oral enzyme supplements to digest dietary gluten, gluten removal by breeding wheat varieties with reduced or deleted gluten toxicity, the development of polymeric binders to suppress gluten induced pathology.

Classical celiac disease is more frequent with a double dose of HLA-DQB1*02: A systematic review with meta-analysis

Background and aims

Experimental data suggest that the HLA-DQ2 gene dose has a strong quantitative effect on clinical outcomes and severity of celiac disease (CD). We aimed to conduct a meta-analysis with systematic review to investigate the association between HLA-DQB1*02 gene doses and the characteristics of CD.

Methods

We searched seven medical databases for studies discussing HLA-DQB1 gene dose in CD and various disease characteristics, such as clinical presentation, histology, age at diagnosis, and comorbidities. Odds ratios (OR, for categorical variables) and weighted mean differences (for age) were calculated to compare patients with a double dose of HLA-DQB1*02 versus those with single and zero doses. Heterogeneity was tested with I²-statistics and explored by study subgroups (children and adults).

Results

Twenty-four publications were eligible for meta-analysis. Classical CD was more frequent with a double versus single dose of the HLA-DQB1*02 allele (OR = 1.758, 95%CI: 1.148–2.692, I² = 0.0%). In pediatric studies, gene dose effect was more prominent (OR = 2.082, 95%CI: 1.189–3.646, I² = 0.0% and OR = 3.139, 95%CI: 1.142–8.630, I² = 0.0% for the comparisons of double versus single and double versus zero dose, respectively). Atrophic histology was more prevalent with a double versus zero dose (OR = 2.626, CI: 1.060–6.505, I² = 21.3%). We observed no gene dose effect regarding diarrhea, age at diagnosis, the severity of villous atrophy, and the association with type 1 diabetes mellitus.

Conclusion

A double dose of HLA-DQB1*02 gene seems to predispose patients to developing classical CD and villous atrophy. Risk stratification by HLA-DQB1*02 gene dose requires further clarification due to the limited available evidence.

Tissue transglutaminase autoantibodies in children with newly diagnosed type 1 diabetes are related to human leukocyte antigen but not to islet autoantibodies: A Swedish nationwide prospective population-based cohort study

OBJECTIVES

This study explored the association between tissue transglutaminase autoantibody (tTGA), high-risk human leucocyte antigen (HLA) genotypes and islet autoantibodies in children with newly diagnosed type 1 diabetes (T1D).

PATIENTS AND METHODS

Dried blood spots and serum samples were taken at diagnosis from children <18 years of age participating in Better Diabetes Diagnosis (BDD), a Swedish nationwide prospective cohort study of children newly diagnosed with T1D. We analyzed tTGA, high-risk HLA DQ2 and DQ8 (DQX is neither DQ2 nor DQ8) and islet auto-antibodies (GADA, IA-2A, IAA, and three variants of Zinc transporter; ZnT8W, ZnT8R, and ZnT8QA).

RESULTS

Out of 2705 children diagnosed with T1D, 85 (3.1%) had positive tTGA and 63 (2.3%) had borderline values. The prevalence of tTGA was higher in children with the HLA genotypes DQ2/2, DQ2/X or DQ2/8 compared to those with DQ8/8 or DQ8/X (p = .00001) and those with DQX/X (p ≤ .00001). No significant differences were found in relation to islet autoantibodies or age at diagnosis, but the presence of tTGA was more common in girls than in boys (p = .018).

CONCLUSION

tTGA at T1D diagnosis (both positive and borderline values 5.4%) was higher in girls and in children homozygous for DQ2/2, followed by children heterozygous for DQ2. Only children with DQ2 and/or DQ8 had tTGA. HLA typing at the diagnosis of T1D can help to identify those without risk for CD.

Expression level of risk genes of MHC class II is a susceptibility factor for autoimmunity: New insights

To date, the study of the impact of major hystocompatibility complex on autoimmunity has been prevalently focused on structural diversity of MHC molecules in binding and presentation of (auto)antigens to cognate T cells. Recently, a number of experimental evidences suggested new points of view to investigate the complex relationships between MHC gene expression and the individual predisposition to autoimmune diseases. Irrespective of the nature of the antigen, a threshold of MHC-peptide complexes needs to be reached, as well as a threshold of T cell receptors engaged is required, for the activation and proliferation of autoantigen-reactive T cells. Moreover, it is well known that increased expression of MHC class II molecules may alter the T cell receptor repertoire during thymic development, and affect the survival and expansion of mature T cells. Many evidences confirmed that the level of both transcriptional and post-transcriptional regulation are involved in the modulation of the expression of MHC class II genes and that both contribute to the predisposition to autoimmune diseases. Here, we aim to focus some of these regulative aspects to better clarify the role of MHC class II genes in predisposition and development of autoimmunity.

Co-occurrence of Type 1 Diabetes and Celiac Disease Autoimmunity

BACKGROUND AND OBJECTIVES

Few birth cohorts have prospectively followed development of type 1 diabetes (T1D) and celiac disease (CD) autoimmunities to determine timing, extent of co-occurrence, and associated genetic and demographic factors.

METHODS

In this prospective birth cohort study, 8676 children at high genetic risk of both diseases were enrolled and 5891 analyzed in median follow-up of 66 months. Along with demographic factors and HLA-DR-DQ, genotypes for HLA-DPB1 and 5 non-HLA loci conferring risk of both T1D and CD were analyzed.

RESULTS

Development of persistent islet autoantibodies (IAs) and tissue transglutaminase autoantibodies (tTGAs), as well as each clinical disease, was evaluated quarterly from 3 to 48 months of age and semiannually thereafter. IAs alone appeared in 367, tTGAs alone in 808, and both in 90 children. Co-occurrence significantly exceeded the expected rate. IAs usually, but not always, appeared earlier than tTGAs. IAs preceding tTGAs was associated with increasing risk of tTGAs (hazard ratio [HR]: 1.48; 95% confidence interval [CI]: 1.15-1.91). After adjusting for country, sex, family history, and all other genetic loci, significantly greater co-occurrence was observed in children with a T1D family history (HR: 2.80), HLA-DR3/4 (HR: 1.94) and single-nucleotide polymorphism rs3184504 at SH2B3 (HR: 1.53). However, observed co-occurrence was not fully accounted for by all analyzed factors.

CONCLUSIONS

In early childhood, T1D autoimmunity usually precedes CD autoimmunity. Preceding IAs significantly increases the risk of subsequent tTGAs. Co-occurrence is greater than explained by demographic factors and extensive genetic risk loci, indicating that shared environmental or pathophysiological mechanisms may contribute to the increased risk.