Increased prevalence of celiac disease without gastrointestinal symptoms in adults MICA 5.1 homozygous subjects from the Campania area

Review article: Becoming and being coeliac-special considerations for childhood, adolescence and beyond

Classically considered a disease of early childhood characterised by malabsorption and failure to thrive, coeliac disease is now recognised to arise in genetically susceptible individuals at any age. Although permissive HLA genotypes are the strongest predictor of coeliac disease, they are not sufficient. Several prospective cohort studies enrolling genetically at-risk infants have investigated the role of potential triggers of coeliac disease autoimmunity, such as timing of gluten introduction, viral infections and dietary patterns. Much less is known about triggers of coeliac disease in adulthood. Better understanding of factors leading to coeliac disease may be helpful in the management of those with potential coeliac disease (elevated serum celiac antibodies without villous atrophy in the small intestine), many of whom initiate a gluten-free diet without demonstration of villous atrophy. There are a range of clinical presentations of celiac disease in childhood and patterns of coeliac serology, including fluctuation and spontaneous reversion on a gluten-containing diet, vary. There is a current debate over best strategies to manage adults and children with potential coeliac disease to avoid over-treatment and under-treatment. Childhood and adolescence carry unique issues pertaining to the diagnosis and management of coeliac disease, and include nutrition and growth, rescreening, repeat biopsy, dietary adherence concerns and transition to adult care. In conclusion, while coeliac disease has similar pathogenesis and general clinical manifestations in paediatric and adult populations, diagnostic and management approaches need to adapt to the developmental stages.

The Role of Natural Killer Group 2, Member D in Chronic Inflammation and Autoimmunity

Current medicine and medical science puts great effort into elucidating the basis of chronicity and finding appropriate treatments for inflammatory diseases; however, the mechanisms driving aberrant immune responses are mostly unknown and deserve further study. Of particular interest is the identification of checkpoints that regulate the function and differentiation of pro-inflammatory cells during pathogenesis, along with means of their modulation for therapeutic purposes. Natural killer group 2, member D (NKG2D) is a potent activator of the immune system, known as a sensor for “induced-self” ligands, i.e., cellular danger signals that, in the context of chronic inflammation and autoimmunity, can be presented by cells being exposed to an inflammatory cytokine milieu, endoplasmic reticulum stress, or cell death. Engagement by such ligands can be translated by NKG2D into activation or co-stimulation of NK cells and different subsets of T cells, respectively, thus contributing to the regulation of the inflammatory response. In this review, we discuss the current knowledge on the contribution of the NKG2D–NKG2DL signaling axis during intestinal inflammation, type 1 diabetes, multiple sclerosis, and rheumatoid arthritis, where the role of NKG2D has been associated either by aberrant expression of the receptor and its ligands and/or by functional data in corresponding mouse models.

High Frequency of Haplotype HLA-DQ7 in Celiac Disease Patients from South Italy: Retrospective Evaluation of 5,535 Subjects at Risk of Celiac Disease

Background

Celiac disease (CD) has a strong genetic component mainly due to HLA DQ2/DQ8 encoding genes. However, a minority of CD patients are DQ2/DQ8-negative. To address this issue, we retrospectively characterized HLA haplotypes in 5,535 subjects at risk of CD (either relatives of CD patients or subjects with CD-like symptoms) referred to our center during a 10-year period.

Methods

We identified loci DQA1/DQB1/DRB1 by sequence-specific oligonucleotide-PCR and sequence-specific primer-PCR; anti-transglutaminase IgA/IgG and anti-endomysium IgA by ELISA and indirect immunofluorescence, respectively.

Results

We diagnosed CD in 666/5,535 individuals, 4.2% of whom were DQ2/DQ8-negative. Interestingly, DQ7 was one of the most abundant haplotypes in all CD patients and significantly more frequent in DQ2/DQ8-negative (38%) than in DQ2/DQ8-positive CD patients (24%) (p<0.05).

Conclusion

Our data lend support to the concept that DQ7 represents an additive or independent CD risk haplotype with respect to DQ2/DQ8 haplotypes but this finding should be verified in other large CD populations.

MICA SNPs and the NKG2D system in virus-induced HCC

Hepatocellular carcinoma (HCC) is one of the most frequent causes of cancer-related death globally. Above well-known risk factors for HCC development ranging from various toxins to diseases such as diabetes mellitus, chronic infection with hepatitis B virus and hepatitis C virus (HCV) poses the most serious threat, constituting the cause in more than 80 % of cases. In addition to the viral genes intensively investigated, the pathophysiological importance of host genetic factors has also been greatly and increasingly appreciated. Genome-wide association studies (GWAS) comprehensively search the host genome at the single-nucleotide level, and have successfully identified the genomic region associated with a whole variety of diseases. With respect to HCC, there have been reports from several groups on single nucleotide polymorphisms (SNPs) associated with hepatocarcinogenesis, among which was our GWAS discovering MHC class I polypeptide-related sequence A (MICA) as a susceptibility gene for HCV-induced HCC. MICA is a natural killer (NK) group 2D (NKG2D) ligand, whose interaction with NKG2D triggers NK cell-mediated cytotoxicity toward the target cells, and is a key molecule in tumor immune surveillance as its expression is induced on stressed cells such as transformed tumor cells for the detection by NK cells. In this review, the latest understanding of the MICA-NKG2D system in viral HCC, particularly focused on its antitumor properties and the involvement of MICA SNPs, is summarized, followed by a discussion of targets for state-of-the-art cancer immunotherapy with personalized medicine in view.

Overview of biomarkers for diagnosis and monitoring of celiac disease

Among the adverse reactions caused by wheat, celiac disease (CD) is the longest studied and best-known pathology. The more recently defined non-celiac gluten sensitivity (NCGS) presents with symptoms which are often indistinguishable from CD. Diagnosis of CD is based on serologic, molecular, and bioptic testing. The IgA anti-transglutaminase (tTG) test is considered highly important, as it shows high sensitivity and specificity and its levels correlate to the degree of intestinal damage. Small bowel biopsy can be avoided in symptomatic patients with IgA anti-tTG levels above 10× the manufacturer's cut-off. Recently, tests of anti-deamidated peptides of gliadin (DGP) have replaced classic anti-native gliadin (AGA) tests. DGP assays have a considerably higher diagnostic accuracy than AGA assays, especially in the IgG class, and can replace anti-tTG tests in patients with selective IgA deficiency. The combination of IgG anti-DGP plus IgA anti-tTG assays show greater sensitivity than a single test, with very high specificity. EMA tests have great diagnostic accuracy but are not recommended by all the latest guidelines because they are observer dependent. Biopsy must still be considered the gold standard for CD diagnosis. HLA-DQ genotyping can be used to screen asymptomatic children and in cases of histology/serology disagreement. About half of NCGS patients are DQ2 positive and have IgG AGA. To diagnose NCGS, first CD and wheat allergy must be excluded; then the wheat dependence of symptoms must be verified by a gluten-free diet and subsequent gluten challenge.

Immunogenetic biomarkers in inflammatory bowel diseases: Role of the IBD3 region

Many studies have demonstrated the linkage between the IBD3 region (6p21.1-23), an area which encompasses the famous human leukocyte antigen (HLA) complex, and Crohn’s disease (CD) or ulcerative colitis (UC). IBD3 is the only region that meets genome-wide significance, and provides stronger evidence of the linkage than 16p13.1-16q12.2 (IBD1), the locus that contains the susceptibility gene CARD15. However, despite these findings, IBD3 susceptibility genes remain elusive and unclear due to the strong linkage disequilibrium, extensive polymorphism, and high gene density that characterize this area and also due to varying allele frequencies in populations around the world. This area presents an extremely high abundance of genes, including the classical and non-classical major histocompatibility complex (MHC) class I and II genes, and other genes, namely MHC class III genes tumor necrosis factor (TNF)-α and -β, and Hsp, whose proteins play key functions in immunological processes. To date, it is not clear which genes within the MHC family contribute to the IBD pathogenesis, although certain HLA alleles have been associated with IBD. Recent insights into the biological function of other genes encoded within the IBD3 region, such as the MHC class I chain-related (MIC) genes, have led investigators to a more comprehensive exploration of this region. MHC class I chain-related molecule A (MICA) is highly polymorphic and interacts with NKG2D, its receptor on the surface of NK, Tγδ and T CD8⁺ cells. Increased expression of MICA in intestinal epithelial cells and increased expression of NKG2D in CD4⁺ T cells (lamina propria) in patients with CD have also been reported. MICA alleles have also been associated with IBD, and a variation at amino acid position 129 of the α2-heavy chain domain seems to categorize MICA alleles into strong and weak binders of NKG2D receptor, thereby influencing the effector cells’ function. In this regard, a relevant role of MICA-129-Val/Met single nucleotide polymorphism has recently been implicated in the pathogenesis of IBD. TNF-α and -β also play an important role in inflammatory response. In fact, IBD is commonly treated with TNF-α inhibitors. Additionally, polymorphisms of TNF-α gene are known to affect the gene expression level and particular TNF-α genotypes may influence the response of IBD patients treated with TNF-α inhibitors.

Evaluation of European coeliac disease risk variants in a north Indian population

Studies in European populations have contributed to a better understanding of the genetics of complex diseases, for example, in coeliac disease (CeD), studies of over 23 000 European samples have reported association to the HLA locus and another 39 loci. However, these associations have not been evaluated in detail in other ethnicities. We sought to better understand how disease-associated loci that have been mapped in Europeans translate to a disease risk for a population with a different ethnic background. We therefore performed a validation of European risk loci for CeD in 497 cases and 736 controls of north Indian origin. Using a dense-genotyping platform (Immunochip), we confirmed the strong association to the HLA region (rs2854275, P=8.2 × 10⁻⁴⁹). Three loci showed suggestive association (rs4948256, P=9.3 × 10⁻⁷, rs4758538, P=8.6 × 10⁻⁵ and rs17080877, P=2.7 × 10⁻⁵). We directly replicated five previously reported European variants (P<0.05; mapping to loci harbouring FASLG/TNFSF18, SCHIP1/IL12A, PFKFB3/PRKCQ, ZMIZ1 and ICOSLG). Using a transferability test, we further confirmed association at PFKFB3/PRKCQ (rs2387397, P=2.8 × 10⁻⁴) and PTPRK/THEMIS (rs55743914, P=3.4 × 10⁻⁴). The north Indian population has a higher degree of consanguinity than Europeans and we therefore explored the role of recessively acting variants, which replicated the HLA locus (rs9271850, P=3.7 × 10⁻²³) and suggested a role of additional four loci. To our knowledge, this is the first replication study of CeD variants in a non-European population.

Autoantibodies against MHC class I polypeptide-related sequence A are associated with increased risk of concomitant autoimmune diseases in celiac patients

BACKGROUND

Overexpression of autologous proteins can lead to the formation of autoantibodies and autoimmune diseases. MHC class I polypeptide-related sequence A (MICA) is highly expressed in the enterocytes of patients with celiac disease, which arises in response to gluten. The aim of this study was to investigate anti-MICA antibody formation in patients with celiac disease and its association with other autoimmune processes.

METHODS

We tested serum samples from 383 patients with celiac disease, obtained before they took up a gluten-free diet, 428 patients with diverse autoimmune diseases, and 200 controls for anti-MICA antibodies. All samples were also tested for anti-endomysium and anti-transglutaminase antibodies.

RESULTS

Antibodies against MICA were detected in samples from 41.7% of patients with celiac disease but in only 3.5% of those from controls (P <0.0001) and 8.2% from patients with autoimmune disease (P <0.0001). These antibodies disappeared after the instauration of a gluten-free diet. Anti-MICA antibodies were significantly prevalent in younger patients (P <0.01). Fifty-eight patients with celiac disease (15.1%) presented a concomitant autoimmune disease. Anti-MICA-positive patients had a higher risk of autoimmune disease than MICA antibody-negative patients (P <0.0001; odds ratio = 6.11). The risk was even higher when we also controlled for age (odds ratio = 11.69). Finally, we found that the associated risk of developing additional autoimmune diseases was 16 and 10 times as high in pediatric patients and adults with anti-MICA, respectively, as in those without.

CONCLUSIONS

The development of anti-MICA antibodies could be related to a gluten-containing diet, and seems to be involved in the development of autoimmune diseases in patients with celiac disease, especially younger ones.

Association analysis of MICA gene polymorphism and MICA-129 dimorphism with inflammatory bowel disease susceptibility in a Spanish population

MICA is located at 46 kb centromeric of HLA-B, is highly polymorphic and interactions with NKG2D, its receptor on the surface of NK, Tgammadelta, and T CD8 lymphocytes. A variation at amino acid position 129 of the alpha2-heavy chain domain seems to categorize MICA alleles into strong and weak binder of NKG2D receptor, and thereby to influence effector cell function. Our aim was to study allele polymorphism of MICA and the functionally relevant dimorphism (129val/met) of MICA gene in inflammatory bowel disease (IBD) patients in our population. DNA was obtained from IBD patients (n = 88) and unrelated healthy Murcians (n = 154) and used to MICA genotyping using polymerase chain reaction-sequence-specific oligonucleotides. We did not find statistical differences in the distribution of MICA alleles between the IBD and control groups. However, we found a higher frequency of MICA-129met/met and a lower frequency of MICA-129val/met genotypes in IBD patients (mainly in ulcerative colitis) than in controls (pc = 0.02). These preliminary data could suggest a relevant role of MICA-129-val/met SNP (weak/strong binders of NKG2D receptor) in the pathogenesis of IBD.

HLA class II polymorphism in children with coeliac disease in Tunisia: is there any influence on clinical manifestation?

OBJECTIVE

To elucidate the HLA DRB1, DQB1 and DQA1 polymorphism in Tunisian children with typical form of coeliac disease (CD) in comparison with those from mass screening (atypical and silent CD).

MATERIALS AND METHODS

We recruited three groups: group I: 40 CD children diagnosed according to the ESPGHAN criteria. group II: 40 healthy controls matched with sex, age and geographic origin. group III: 38 CD children coming from mass screening in schoolchildren. HLA class II DRB1, DQB1 and DQA1 alleles were typed by PCR-sequence-specific primer.

RESULTS

Comparing the groups I and II, we found a pronounced increase of the susceptible alleles HLA DRB1*03 (relative risk, RR = 4.18, Pc = 0.001), DQB1*02 (RR = 7.9, Pc<0.0001) and DQA1*0501 (RR = 4.1, Pc = 0.001). As for protective alleles, we detected a high frequency of DRB1*13 (RR = 0.059, Pc = 0.001), DQA1*0102 (RR = 0.071, Pc = 0.009) and DQB1*06 (RR = 0.125, Pc = 0.0042). Haplotype analysis showed that the main combination observed was the conformation of DQ2 (DQA1*0501-DQB1*02) in 36 patients from group I and 30 from group III. There was no statistically significant difference between the groups I and III according to the distribution of the different alleles.

CONCLUSION

We confirmed in this study the high frequency of DQ2 haplotype in CD patients and we identified new protective alleles DRB1*13, DQA1*0102 and DQB1*06. However, HLA polymorphism seems to have no evident impact on clinical outcome of CD.