Celiac disease and HLA in a Bedouin kindred

Haplotype-dependent HLA-DRB1-DQB1 susceptibility to occult HBV infection in Xi'an Han population

BACKGROUND

Occult hepatitis B virus (HBV) infection (OBI) is primarily characterized by the persistence of HBV-DNA in the liver tissues and/or in the serum without detectable HBsAg. Human leukocyte antigen (HLA) polymorphisms have been found to be strongly associated with HBV in different ethnic backgrounds. The association of HLA-DRB1-DQB1 haplotypes with OBI has not been previously reported in China. The aim of this study was to identify the potential association of HLA-DRB1-DQB1 haplotypes that may be involved in OBI genetic susceptibility.

METHODS

A case-control study was conducted between 107 OBI subjects and 280 healthy controls from the blood donors in the Shaanxi Province Blood Center. The HLA-DRB1, DQB1 loci were genotyped using polymerase chain reaction-sequence based typing (PCR-SBT). Based on the genotype data of the two loci, haplotype estimation was performed.

RESULTS

HLA-DRB1*07:01-DQB1*02:02 (pc = 0.344 × 10^-3 , OR = 3.489, 95%CI = 2.000-6.088) and HLA-DRB1*09:01-DQB1*03:03 (pc = 0.02, OR = 2.370, 95%CI = 1.450-3.873) serve as the possible risk and susceptibility haplotypes for OBI in Xi'an Han after Bonferroni correction.

CONCLUSIONS

This study demonstrated that HLA II haplotypes were significantly associated with OBI in the Xi'an Han population. To the best of our knowledge, this is the first study to associate HLA-DRB1-DQB1 haplotypes with OBI, which can provide valuable insights into the relationship between the various genetic factors and immune responses in the Xi'an population. The findings can also form the basis for future studies about the role of HLA in OBI.

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.

Exome sequencing of 75 individuals from multiply affected coeliac families and large scale resequencing follow up

Coeliac disease (CeD) is a highly heritable common autoimmune disease involving chronic small intestinal inflammation in response to dietary wheat. The human leukocyte antigen (HLA) region, and 40 newer regions identified by genome wide association studies (GWAS) and dense fine mapping, account for ∼40% of the disease heritability. We hypothesized that in pedigrees with multiple individuals with CeD rare [minor allele frequency (MAF) <0.5%] mutations of larger effect size (odds ratios of ∼2-5) might exist. We sequenced the exomes of 75 coeliac individuals of European ancestry from 55 multiply affected families. We selected interesting variants and genes for further follow up using a combination of: an assessment of shared variants between related subjects, a model-free linkage test, and gene burden tests for multiple, potentially causal, variants. We next performed highly multiplexed amplicon resequencing of all RefSeq exons from 24 candidate genes selected on the basis of the exome sequencing data in 2,248 unrelated coeliac cases and 2,230 controls. 1,335 variants with a 99.9% genotyping call rate were observed in 4,478 samples, of which 939 were present in coding regions of 24 genes (Ti/Tv 2.99). 91.7% of coding variants were rare (MAF <0.5%) and 60% were novel. Gene burden tests performed on rare functional variants identified no significant associations (p<1×10(-3)) in the resequenced candidate genes. Our strategy of sequencing multiply affected families with deep follow up of candidate genes has not identified any new CeD risk mutations.

Celiac disease in the developing world

The prevalence of celiac disease (CD) in many developing countries is similar to that of developed areas, in both low- and high-risk groups. The disorder is underestimated because of lack of disease awareness. CD is strongly associated with HLA-DQ2 in developing countries. Clinical presentation may be characterized by chronic diarrhea, anemia, stunting and increased mortality. Few studies have addressed atypical or silent CD. Diagnosis is initially made by serologic tests and is confirmed by small intestinal biopsies. In developing countries the adherence to the treatment is still difficult because of poor availability of dedicated gluten-free food.

The Prevalence of the Celiac Disease Among Urban Bedouin Population in Israel

Background

Celiac disease (CD) is a common, but often under-diagnosed condition with possible serious complications. CD, having a prevalence of about 1% is more common than once thought. Only limited research is available comparing differences between adults and children. A comprehensive Medline search was conducted. No data was found concerning the prevalence of CD among the adult Bedouin population.

Methods

The research is retrospective and descriptive. The objective of our research was to determine the prevalence of the CD within adult and child Bedouin populations in urban Israel. A report of all of diagnosed CD patients extracted from the medical computerized information system (“Clicks”).

Results

In our sample we found the prevalence was 0.51% in children and 0.12% in adults.

Conclusion

In our opinion, one of reasons for the low prevalence level in the Bedouin community might be that typical CD symptoms are less prominent in Bedouin communities than in other communities. But no doubt hypo-diagnosis does exist. We suppose more advanced research about the nature and typical clinical manifestations of CD within the Bedouin population need to be investigated. Medical personnel working within the Bedouin community needs information concerning CD and the characteristics of diagnosis and treatment in the Bedouin community. The Bedouin community itself needs more information concerning CD and the importance of treatment, which could also improve early diagnosis and compliance.

Variants within protectin (CD59) and CD44 genes linked to an inherited haplotype in a family with coeliac disease

Coeliac disease (CD) is an autoimmune disorder characterised by inflammation, villous atrophy and hyperplasia of the small intestinal mucosa that affects genetically susceptible individuals. A genome-wide scan was performed in 17 family members with high incidence of CD. Highest nonparametric linkage (NPL) and logarithm of odds (LOD) scores were of 6.21 (P = 0.0107) and 2.57, respectively, to a region on chromosome 11p13-12. Following fine mapping, NPL and LOD scores did not change, but the linkage interval on chromosome 11 was narrowed to a region that is approximately 50.94 cM from pTer. Two inherited haplotypes on chromosomes 11p13-12 and 9q21 were observed in all affected members but not in the majority of clinically normal individuals. Sequencing of genes at region 11p13-12 showed a number of sequence variants, two of which were linked with the inherited haplotype. One of these variants in the CD59 gene was found at a very low frequency in the population and could possibly affect pre-messenger RNA splicing. This study is of particular importance for the identification of novel genes that might be responsible for CD other than human leukocyte antigen.

Prospective human leukocyte antigen, endomysium immunoglobulin A antibodies, and transglutaminase antibodies testing for celiac disease in children with Down syndrome

OBJECTIVE

To assess the effect of a prospective screening strategy for the early diagnosis of celiac disease (CD) in children with Down syndrome (DS).

STUDY DESIGN

Blood samples were taken from 155 children with DS. Buccal swabs were also taken from 9 of these children for determination of human leukocyte antigen (HLA)-DQ2 or HLA-DQ8 positivity. Independently, immunoglobulin A anti-endomysium-(EMA) and anti-tissue transglutaminase antibodies (TGA) were tested. An intestinal biopsy was performed to confirm the diagnosis of CD.

RESULTS

Sixty-three children (40.6%) had test results that were positive for HLA-DQ2 or HLA-DQ8. Results of HLA DQ-typing of DNA isolated from blood and buccal swabs were identical. Eight of the children in whom test results were positive for HLA-DQ2/8 also had positive test results for EMA and TGA. CD was confirmed in 7 of these children with an intestinal biopsy, and in 1 child, CD was suggested with improvement on a gluten-free diet.

CONCLUSIONS

We found a prevalence of CD in children with DS of 5.2% (10 times higher than the general Dutch population). We recommend HLA-DQ2/8 typing from buccal swabs in the first year of life and initiating serologic screening of children with DS in whom test results are positive for HLA-DQ2 or DQ8 at age 3 years. Early knowledge of negative HLA-DQ2/8 status can reassure most parents that their children do not have a CD risk.

Adverse drug reactions and pharmacogenomics: recent advances

The concept of pharmacogenomics, the study of how variation in the human genome affects response to drugs, attracts attention from clinicians and the pharmaceutical industry alike. The aim is to distinguish, using appropriate genetic tests, individuals who may be harmed by certain drugs from those who may benefit from them. Adverse drug reactions cause significant morbidity and mortality and incur a large cost to healthcare systems. Pharmacogenomics may help in the prediction and prevention of adverse reactions to drugs. While some recent studies (e.g., abacavir hypersensitivity) have shown strong associations with single genetic factors, whether these represent the exceptions rather than the rule is unclear. Further studies on adverse drug reaction pharmacogenetics are needed – these should be adequately powered and utilize the most appropriate study design that allows for an evaluation of both genetic and environmental factors. For pharmacogenetic testing to become acceptable in clinical practice, it is important that such studies are also able to provide evidence of clinical validity and clinical utility.

An autosomal genome-wide screen for celiac disease in Bedouin families

Celiac disease is a common, familial autoimmune disease caused by exposure to gliadin in wheat, and related prolamins in barley and rye. The prevalence of the disease is approximately 1:133. Celiac disease can cause significant morbidity. The only treatment is a gluten-free diet. A genome-wide search of 405 microsatellite markers was performed on samples from 18 Bedouin families with a minimum of two cases of celiac disease. Non-parametric and parametric (including both dominant and recessive models of inheritance) linkage analyses were performed. The most significant genome-wide linkage evidence was at chromosome 3p26 with an HLod of 3.21, under the dominant model. The only other HLod or NPL greater than 2 was at 4q35, with an HLod of 2.15 under a dominant model. The region at 3p26, previously reported in two linkage analyses, harbors interleukin receptor genes, plausible candidates for celiac disease.

Differential effects of DRB1*0301 and DQA1*0501-DQB1*0201 on the activation and progression of islet cell autoimmunity

Autoimmune diabetes shows extreme variation in age of onset and clinical presentation, although most studies have been done in children with the most severe subtype. Disease risk is strongly associated with HLA-DRB1*0301-DQA1*0501-DQB1*0201 (DR3-DQ2), but it has not been possible to separate the effects of the DR and DQ alleles. We have identified a large Bedouin kindred in which a high prevalence of islet autoimmunity is associated with two different DR3 haplotypes, one carrying the usual DQ2 and the other carrying DQA1*0102-DQB1*0502 (DQ5). Results of prospective follow-up studies indicate that DR3 is associated with the initial activation of islet autoimmunity whereas DQ2 is associated with early-onset and severe clinical disease. The association signals map to a 350-kb interval, thus implicating primary effects for DR3 and DQ2. Overall, our results emphasize the importance of prospective genetic studies that examine the full range of variation in the initiation, progression and expression of autoimmune disease.