Pediatric celiac disease in India is associated with multiple DR3-DQ2 haplotypes

Shared and distinct genetics of pure type 1 diabetes and type 1 diabetes with celiac disease, homology in their auto-antigens and immune dysregulation states: a study from North India

AIM

This study was undertaken to explicate the shared and distinctive genetic susceptibility and immune dysfunction in patients with T1D alone and T1D with CD (T1D + CD).

METHODS

A total of 100 T1D, 50 T1D + CD and 150 healthy controls were recruited. HLA-DRB1/DQB1 alleles were determined by PCR-sequence-specific primer method, SNP genotyping for CTLA-4 and PTPN22 was done by simple probe-based SNP-array and genotyping for INS-23 Hph1 A/T was done by RFLP. Autoantibodies and cytokine estimation was done by ELISA. Immune-regulation was analysed by flow-cytometry. Clustering of autoantigen epitopes was done by epitope cluster analytical tool.

RESULTS

Both T1D alone and T1D + CD had a shared association of DRB1*03:01, DRB1*04, DRB3*01:07/15 and DQB1*02. DRB3*01:07/15 confers the highest risk for T1D with relative risk of 11.32 (5.74-22.31). Non-HLA gene polymorphisms PTPN22 and INS could discriminate between T1D and T1D + CD. T1D + CD have significantly higher titers of autoantibodies, expression of costimulatory molecules on CD4 and CD8 cells, and cytokine IL-17A and TGF-β1 levels compared to T1D patients. Epitopes from immunodominant regions of autoantigens of T1D and CD clustered together with 40% homology.

CONCLUSION

Same HLA genes provide susceptibility for both T1D and CD. Non-HLA genes CTLA4, PTPN22 and INS provide further susceptibility while different polymorphisms in PTPN22 and INS can discriminate between T1D and T1D + CD. Epitope homology between autoantigens of two diseases further encourages the two diseases to occur together. The T1D + CD being more common in females along with co-existence of thyroid autoimmunity, and have more immune dysregulated state than T1D alone.

Human Leukocyte Antigen-DQ Genotyping in Pediatric Celiac Disease

PURPOSE

The purpose of this study was to determine the pattern of human leukocyte antigen (HLA)-DQ genotype in children diagnosed with celiac disease (CD) (biopsy proven), and to compare this with a control group; and secondarily, to correlate HLA genotypes with clinical profiles of CD.

METHODS

This cross-sectional comparative observational study included 26 controls and 52 patients diagnosed with CD who presented at Sir Padampat Mother and Child Health Institute, Jaipur, from May, 2017 to October, 2018. HLA DQ genotype was assessed for each patients and correlated with clinical profiles.

RESULTS

HLA DQ2/DQ8 genotypes were significantly more common in CD (present in 100.0% cases) than in controls (23.1%) in Northern India (Rajasthan). When HLA DQ2.5 and DQ8 were present together, individuals had significantly more atypical presentations and severe findings on duodenal biopsy. Similarly, patients with the HLA DQ 2.5 genotype were also predisposed to more severe endoscopic findings, while HLA DQ2.2 predisposed them to less severe biopsy findings. HLA DQ8 was significantly associated with later age at diagnosis (>5 years) and shorter stature. The highest HLA DQ relative risk (RR) for CD development was associated with HLA DQ2.5 and DQ2.2 in combination, followed by HLA DQ2.5 and DQ8 in combination, while HLA DQx.5 and HLA DQ2.2 together had the lowest risk.

CONCLUSION

HLA DQ2/DQ8 genotypes are strongly associated with pediatric CD patients in northern India. These genotypes and their combinations may be associated with different clinical presentations of CD, and may help predict severity of CD.

Prevalence and epidemiological profile of celiac disease in children with type 1 diabetes mellitus: Experience from a tertiary care center of India

BACKGROUND

The HLA associations of celiac disease (CD) in north Indians differ from that in Europeans. Our dietary gluten is among the highest in the world. Data on CD in people with diabetes (PWD) in north India is scant.

OBJECTIVE

To estimate the prevalence and clinical profile of CD in children with type 1 diabetes (T1D).

RESEARCH DESIGN AND METHODS

Retrospective review of case records of PWD with onset ≤18 years of age, registered between 2009 and 2020, having at least one anti tissue-transglutaminase (anti-tTG) serology report.

RESULTS

Of 583 registered PWD, 398 (68.2%) had celiac serology screening. A positive report was obtained in 66 (16.6%). Of 51 biopsied people, 22 (5.5%) were diagnosed to have CD, 12 in the first 2 years of diabetes onset. Symptomatic CD at diagnosis was seen in 63% (14/22). Age at diabetes onset (median [IQR] age 5.5 years, [2-12]) was lower in PWD and CD compared to PWD alone (10 years, [7-14], p < 0.016). Of 36 biopsied children with anti-tTG >100 au/ml, 20 (55.5%) had CD, while 2 out of 15 (13.3%) of those with lower anti-tTG titer had histopathology suggestive of CD. Of 23 seropositive children not diagnosed with CD, 5 of 8 with anti tTG >100 au/ml, and all 15 with lower anti-tTG, had normalization of titers over the 24 (10-41) months.

CONCLUSIONS

Our prevalence of CD is comparable to international data. Celiac disease was common with younger age at onset of T1D and higher titer of celiac serology. A high proportion was symptomatic of CD at diagnosis.

Human leukocyte antigen (HLA)-DQ2 and -DQ8 haplotypes in celiac, celiac with type 1 diabetic, and celiac suspected pediatric cases

Celiac disease (CD) is an autoimmune enteropathy triggered by ingestion of gluten present in wheat, barley, and rye. Gluten along with environmental trigger starts an inflammatory reaction which results in damage to small intestine. Human leukocyte antigen (HLA)-DQA1∗05, -DQB1∗02, and -DQB1∗03:02 are the known risk alleles of CD. The diagnostic method for CD involves serological or intestinal biopsy, but genetic test could be implemented. HLA typing precludes the need for further diagnosis and it has high negative predictive value. The aim of this study was to make aware of HLA molecular typing for celiac disease among local laboratories and healthcare professionals. The prevalence and frequency distribution of HLA-DQ2 and -DQ8 haplotypes in 175 pediatric unrelated healthy controls, celiac patients, and CD with concurrent diabetes mellitus type 1 (DM1) was evaluated. The most common haplotype was DQ2 followed by DQ8. In control group only DQ2 was observed with frequency of 8.5%. In celiac patients 85.7% were DQ2, 11.4% were DQ8, and rest were DQ2/DQ8 (2.8%), and all had CD. In the group of CD with DM1, 31.4% had DQ2, 25% had DQ8, and 34% having both the haplotypes; while only 9 of these patients were suffering from CD. It was concluded that Celiac disease is frequently unrecognized by physicians, in part because of its variable clinical presentation and symptoms. Thus genetic testing for celiac disease could be an additive tool for diagnosis to exclude ambiguity.

HLA-DRB1* and DQB1* allele and haplotype diversity in eight tribal populations: Global affinities and genetic basis of diseases in South India

The distribution of HLA class-II DRB1* and DQB1* alleles/ haplotypes were studied in 438 individuals of 8 Dravidian tribal groups inhabiting the Western Ghats, south India. The HLA typing was performed by PCR-SSP method. In order to identify the 5-locus Ancestral Extended Haplotypes (AEH), the alleles of HLA-A, -B and -C loci were typed for DNAs with predominant 2-locus haplotypes. The analyses have revealed allele HLA-DRB1*15 as the most predominant allele (Lowest / Highest range: Urali, 14.81 / Malasar, 48.94), followed by the alleles DRB1*10 (Katunayakan, 1.85 / Paliyan, 48.21), DRB1*14 (Paliyan 4.46 / Katunayakan, 40.74), DRB1*12 (Mannan, 1.64 / Katunayakan, 20.37) and DRB1*03 (Mannan, 1.64 / Urali, 29.63). The most frequent DQB1* alleles were DQB1*02 (Paliyan 3.57 / Urali, 23.15), DQB1*05 (Katunayakan, 27.77 / Paliyan 84.82) and DQB1*06 (Malasar, 8.51 / Kuruman, 33.51). The most predominant two-locus haplotypes observed were DRB1*15-DQB1*05, DRB1*10-DQB1*05, DRB1*15-DQB1*06 and DRB1*04-DQB1*05. The present study of HLA immunogenetics of south Indian tribes have revealed the presence of globally shared two and 5-locus haplotypes. Many of these haplotypes were implicated in a number of diseases in south India. We observed the presence of ancestral extended haplotypes (AEHs), hitherto not reported in Indian populations such as, A*68-B*35-C*02-DRB1*15:01-DQB1*05:01, A*24-B*57-C*06-DRB1*04:01-DQB1*05:01 and A*24-B*35-C*02-DRB1*15:01-DQB1*05:02. The dendrogram based phylogenetic analyses have revealed the Caucasian affinity of Urali, palaeo-Mediterranean and Indo-European affinity of Malasar tribes. The presence of globally shared susceptible and protective haplotypes reiterated the mosaic immunogenetic fabric of south Indian tribes.

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.

Celiac Disease in Asia

Celiac disease, once thought to be very uncommon in Asia, is now emerging in many Asian countries. Although the absolute number of patients with celiac disease at present is not very high, this number is expected to increase markedly over the next few years/decades owing to increasing awareness. It is now that the medical community across the Asia should define the extent of the problem and prepare to handle the impending epidemic of celiac disease in Asia.

Pediatric Celiac Disease in Central and East Asia: Current Knowledge and Prevalence

The current prevalence of pediatric Celiac Disease (CD) is estimated to be around 1% in the general population, worldwide. However, according to the geographic area, a great variability of CD prevalence has been described. Whereas a number of studies are available from Europe, North and South America, Australia, South-West Asia, and North Africa, the knowledge and awareness of CD in large parts of the remaining world areas is definitively poor. In several countries of Central and East Asia, the consumption of wheat is consistent and/or has significantly increased in recent decades, and CD is supposed to be underdiagnosed in children. In this mini-review, we aimed to summarize the current knowledge about the prevalence of pediatric CD in Central and East Asia, paying attention to the HLA-DQ immunogenetic background as well. Indeed, CD is likely not to be as uncommon as previously or currently thought in countries like Russia, Kazakhstan, and China, in addition to India, where pediatric CD has been clearly showed to be quite prevalent. Therefore, there is an urgent need for population-based studies on the prevalence of CD in those countries, especially in children, in order to increase the awareness of this disease and to improve the diagnostic strategy in these areas.

Cross-Talk Between Gluten, Intestinal Microbiota and Intestinal Mucosa in Celiac Disease: Recent Advances and Basis of Autoimmunity

Celiac disease (CD) is an autoimmune disorder of the small intestine, caused by gluten induced inflammation in some individuals susceptible to genetic and environmental influences. To date, pathophysiology of CD in relation to intestinal microbiota is not known well. This review relies on contribution of intestinal microbiome and oral microbiome in pathogenesis of CD based on their interactions with gluten, thereby highlighting the role of upper gastrointestinal microbiota. It has been hypothesized that CD might be triggered by additive effects of immunotoxic gluten peptides and intestinal dysbiosis (microbial imbalance) in the people with or without genetic susceptibilities, where antibiotics may be deriving dysbiotic agents. In contrast to the intestinal dysbiosis, genetic factors even seem secondary in disease outcome thus suggesting the importance of interaction between microbes and dietary factors in immune regulation at intestinal mucosa. Moreover, association of imbalanced counts of some commensal microbes in intestine of CD patients suggests the scope for probiotic therapies. Lactobacilli and specific intestinal and oral bacteria are potent source of gluten degrading enzymes (glutenases) that may contribute to commercialization of a novel glutenase therapy. In this review, we shall discuss advantages and disadvantages of food based therapies along with probiotic therapies where probiotic therapies are expected to emerge as the safest biotherapies among other in-process therapies. In addition, this review emphasizes on differential targets of probiotics that make them suitable to manage CD as along with glutenase activity, they also exhibit immunomodulatory and intestinal microbiome modulatory properties.

HLA-DQ genetics in children with celiac disease: a meta-analysis suggesting a two-step genetic screening procedure starting with HLA-DQ β chains

BackgroundSpecific HLA-DQ genes have been recognized as necessary - but not sufficient - factors for the occurrence of Celiac Disease (CD). Through a meta-analysis, evaluating the distribution of CD-related HLA genotypes in children, we aimed at providing insights for a potential widened screening strategy.MethodsAfter a systematic search on the association between class II HLA genes and CD in children, 46 publications were obtained and assessed for eligibility. A total of 13 eligible studies were submitted to data extraction and analysis (10 case-control studies and 3 cohort studies). Case-control studies collectively enrolled 740 CD patients and 943 controls.ResultsIn the population-stratified analysis, the following alleles conferred a significantly increased risk for CD: HLA-DQB1*02 (odds ratio [OR]=10.28) and HLA-DQB1*03:02 (OR=2.24). By drafting a risk gradient to develop CD according to HLA genetic background, the highest risk is confirmed to exist for DQ2/DQ2 homozygous subjects, regardless of the ethnicities (OR=5.4). Actually, the genotype DQ2/β2 showed basically the same risk (OR=5.3). Indeed, no differences have been found in CD risk between DQ2/β2 and DQ2/DQ2, as well as between DQ8/β2 and DQ2/DQ8, and between β2/DQX and DQ2/X.ConclusionThe HLA-DQB1*02:01 allele is present in more than 90% CD children. In the perspective of a widened pediatric population screening for CD, a double-step process might be suggested: HLA-DQB1*02:01 might be investigated first and, only if this result is positive, children might be candidate for a prospective serologic screening, as a second step.

The incidence of HLA-DQ2/DQ8 in Turkish children with celiac disease and a comparison of the geographical distribution of HLA-DQ

Introduction

Celiac disease (CD) is an auto-immune enteropathy that occurs in genetically pre-disposed people as a result of the consumption of gluten-containing foods.

Aim

To identify the incidence of HLA-DQ2 and HLA-DQ8 observed in children with CD.

Material and methods

In this study, we focused on children ranging in age from 2 to 18 years and diagnosed with celiac disease. In our patients diagnosed with CD, in addition to tissue transglutaminase antibodies (anti-tTG), we also evaluated HLA-DQ2 B1 and HLA-DQ8 B1 alleles using the method of polymerase chain reaction (PCR)/sequence-specific oligonucleotide probes (Luminex^®). The detection of 0201/0202 for HLA-DQ2 allele and 0302 for HLA-DQ8 allele was accepted as a positive result.

Results

The mean age of our patients with celiac disease was 7.42 ±3.18 years, and the female/male ratio was 1.5/1. Seventy-six percent of our patients were HLA-DQ2 and/or HLA-DQ8 positive, 67% were HLA-DQ2 positive, and 25% were HLA-DQ8 positive. Nevertheless, 24% of them were HLA-DQ2 and HLA-DQ8 negative. The incidence of HLA-DQ2 in the control group was 18.8% with a significant difference compared to the HLA-DQ2 incidence in the patient group (67%) (p < 0.05). Similarly the HLA-DQ8 incidence in the control group (5.7%) was significantly lower than the incidence in the patient group (25%) (p < 0.05).

Conclusions

The incidence of the patients diagnosed with CD, who are HLA-DQ2 and HLA-DQ8 negative, varies among different populations.

Morphologic Spectrum of Duodenal Biopsies in Malabsorption: A Study from Southern India

INTRODUCTION

Duodenal endoscopic biopsy is a common investigation for various non-neoplastic conditions. Malabsorption is a common indication for duodenal biopsy in our setting.

AIM

Our study was undertaken to study the morphologic spectrum of non-neoplastic conditions of duodenum emphasizing on Intraepithelial Lymphocytes (IELs) and to have a clinico-pathologic correlation.

MATERIALS AND METHODS

This was a prospective descriptive study. Duodenal biopsies from 101 patients with symptoms of malabsorption were studied according to inclusion and exclusion criteria. Informed written consent was taken. Clinical, laboratory, endoscopic, and serological parameters were collected wherever available. Histomorphological parameters were studied on Haematoxylin and Eosin (H&E) stained sections. Intraepithelial lymphocyte counts were done on CD3, CD4 and CD8 Immunohistochemical (IHC) stained sections and correlated.

RESULTS

We studied 101 duodenal biopsies. Our spectrum included 16 patients of celiac disease (CD) (15.8%), 15 autoimmune duodenitis (14%), 13 nutritional deficiency associated duodenitis (12.8%), five infectious duodenitis (5%) and 41 patients of non-specific duodenitis (40.6%) and 10.9% miscellaneous causes of duodenitis. Villous crypt architecture, IEL counts; villous tip IEL counts were statistically significant between CD and other disease groups.

CONCLUSION

A constellation of clinical, serological, endoscopic and histopathologic features is essential in diagnosing CD and autoimmune duodenitis. Biopsy is also a useful tool in diagnosing infectious duodenitis that are missed in other investigations.

HLA Profile of Celiac Disease among First-Degree Relatives from a Tertiary Care Center in North India

OBJECTIVE

To study the prevalence of Celiac disease (CD) in first-degree relatives (FDR) of CD children.

METHODS

This observational study was performed in FDR (parents and siblings) of consecutive newly diagnosed cases of CD enrolled from January 2011 through March 2012. Screening for CD in FDR was done using IgA tissue transglutaminase (tTG) levels in serum and the seropositive subset underwent upper gastrointestinal (UGI) endoscopy and biopsy to confirm the disease. In addition, HLA analysis for CD was performed in most of the index cases and FDR.

RESULTS

Of 202 FDR of the 64 index cases with CD, 17.3 % (35/202) were seropositive for IgA tTG while confirmed biopsy proven CD was diagnosed in 10.2 % (8/78) of children and 8.1 % (10/124) of adults. HLA DQ2/DQ8 was positive in 96.7 % of the index cases and all FDR with confirmed CD.

CONCLUSIONS

The prevalence of CD among FDR is 9 fold higher than the general population. High prevalence of CD in presence of anemia and short stature in seropositive FDR in index study indicates need of targeted screening of this subgroup for the presence of CD.CD is unlikely in the absence of HLADQ2/DQ8.

Prevalence of Adult Celiac Disease in India: Regional Variations and Associations

OBJECTIVES

Although celiac disease (CeD) affects 1% of people in the northern part of India, it is believed to be uncommon in the southern and northeastern parts because of significant differences in dietary pattern and ethnicity. We estimated the prevalence of CeD in these three populations. In a subset, we also investigated differences in the prevalence of HLA-DQ 2/8 allelotype and dietary grain consumption.

METHODS

A total of 23,331 healthy adults were sampled from three regions of India-northern (n=6207), northeastern (n=8149), and southern (n=8973)-and screened for CeD using IgA anti-tissue transglutaminase antibody. Positive tests were reconfirmed using a second ELISA. CeD was diagnosed if the second test was positive and these participants were further investigated. A subsample of participants was tested for HLA-DQ2/-DQ8 and underwent detailed dietary evaluation.

RESULTS

Age-adjusted prevalence of celiac autoantibodies was 1.23% in northern, 0.87% in northeastern, and 0.10% in southern India (P<0.0001). Prevalence of CeD and latent CeD, respectively, was 8.53/1,000 and 3.70/1,000 in northern, 4.66/1,000 and 3.92/1,000 in northeastern, and 0.11/1,000 and 1.22/1,000 in the southern part. The population prevalence of genes determining HLA-DQ2 and/or -DQ8 expression was 38.1% in northern, 31.4% in northeastern, and 36.4% in southern India. Mean daily wheat intake was highest in northern (455 g) compared with northeastern (37 g) or southern part (25 g), whereas daily rice intake showed an inverse pattern.

CONCLUSIONS

CeD and latent CeD were most prevalent in northern India and were the least in southern India. The prevalence correlated with wheat intake and did not reflect differences in the genetic background.

Celiac disease screening in southern and East Asia

Until 1970s, celiac disease (CD) was considered to be an uncommon disease except in Western Europe. The global epidemiology of CD continues to evolve with improvement in the diagnostic tests, simplification of the diagnostic criteria and increase in awareness about the disease. The Asian region is currently at the crossroads of the frontier of knowledge and awareness of CD. In many Asian nations, CD is still considered to be either nonexistent or very rare. A notable exception is India, where CD has been well recognized, especially in the northern part, and 2 population-based studies have revealed a prevalence of 0.3-1.04%. Initial reports from Malaysia, China, Japan and Singapore suggest the existence of CD in these countries. Furthermore, a meta-analysis of the predisposing factors predicts a high probability of occurrence of CD in fair numbers in China. There are no formal reports on CD from Malaysia, Indonesia, Korea, Taiwan and many other nations in this region. With the impending CD epidemic in Asia, there are many challenges. Some of the efforts which are required include determination of prevalence of CD across the region, spreading of awareness among physicians and patients, training of dieticians for proper counseling and supervision of patients, creation of gluten-free food infrastructure in the food supply and creation of patient advocacy organizations. Although the absolute number of patients with CD at present is not very large, this number is expected to increase over the next few years/decades. It is thus appropriate that the medical community across Asia define the extent of the problem and get prepared to handle the impending CD epidemic.

The Raikas - a unique combination of high prevalence of type 1 diabetes susceptibility genes and near zero incidence of the disease

The Raikas, a camel rearing tribal group living in the Thar desert of Rajasthan has been reported with a very low incidence of diabetes. We analysed the frequency distribution of HLA alleles in this community and compared the same with the non-Raika group living in the same geographic location and also that of the healthy North Indian (NI) population. The data revealed an exceptionally high phenotype frequency of HLA-DRB1*03 in this community (53%) as compared to the non-Raika group (27.73%, p=7.9E-05) and the NI population (14.6%, p=7.65E06). Further analysis revealed the occurrence of four major DRB1*03 haplotypes in the Raikas: (i) A*26-B*08-DRB1*03 (AH8.2, 11.76%); (ii) A*24-B*08-DRB1*03 (AH8.3, 8.82%); (iii) A*02-B*08-DRB1*03 (3.78%); (iv) A*01-B*08-DRB1*03 (AH8.1v, 0.84%); all of which occurred with a several fold higher frequency in the Raikas than the other two groups. These haplotypes have been reported to be positively associated with T1D in the NI population. The apparent lack of T1D and/or other autoimmune diseases in the Raikas despite the higher occurrence of known disease associated HLA alleles/haplotypes is intriguing and highlights the quintessential role of the environmental factors, food habits and level of physical activity in the manifestation of T1D. Possible influence of other protection conferring genes located on, as yet undefined chromosomal locations cannot be ruled out.

Issues associated with the emergence of coeliac disease in the Asia–Pacific region: a working party report of the World Gastroenterology Organization and the Asian Pacific Association of Gastroenterology

BACKGROUND AND AIM

Once thought to be uncommon in Asia, coeliac disease (CD) is now being increasingly recognized in Asia–Pacific region. In many Asian nations, CD is still considered to be either nonexistent or very rare. In recognition of such heterogeneity of knowledge and awareness, the World Gastroenterology Organization and the Asian Pacific Association of Gastroenterology commissioned a working party to address the key issues in emergence of CD in Asia.

METHODS

A working group consisting of members from Asia–Pacific region, Europe, North America, and South America reviewed relevant existing literature with focus on those issues specific to Asia–Pacific region both in terms of what exists and what needs to be done.

RESULTS

The working group identified the gaps in epidemiology, diagnosis, and management of CD in Asian–Pacific region and recommended the following: to establish prevalence of CD across region, increase in awareness about CD among physicians and patients, and recognition of atypical manifestations of CD. The challenges such as variability in performance of serological tests, lack of population-specific cut-offs values for a positive test, need for expert dietitians for proper counseling and supervision of patients, need for gluten-free infrastructure in food supply and creation of patient advocacy organizations were also emphasized.

CONCLUSIONS

Although absolute number of patients with CD at present is not very large, this number is expected to increase over the next few years or decades. It is thus appropriate that medical community across the Asia–Pacific region define extent of problem and get prepared to handle impending epidemic of CD.

Exploring anthropometric and laboratory differences in children of varying ethnicities with celiac disease

BACKGROUND

Celiac disease (CD) is a common autoimmune disorder with an increasing prevalence, including in ethnic minorities.

OBJECTIVE

To report the frequency of CD diagnosis in ethnic minorities presenting to a Canadian pediatric celiac clinic and to determine whether ethnic differences exist at diagnosis or follow-up.

METHODS

Patients with biopsy-proven CD diagnosed at a multidisciplinary celiac clinic between 2008 and 2011 were identified through the clinic database. Data at referral, and six-month and 12-month follow-ups were collected. These included demographics, self-reported ethnicity, symptoms, anthropometrics and laboratory investigations, including serum immunoglobulin antitissue transglutaminase (aTTG).

RESULTS

A total of 272 patients were identified; 80% (n = 218) were Caucasian (group 1) and 20% (n = 54) were other ethnicities. South Asians (group 2) comprised 81% (n = 44) of the minority population. No differences in age or sex were found between the two groups. Group 1 patients presented more often with gastrointestinal symptoms (71% versus 43%; P < 0.001), while patients in group 2 presented more often with growth concerns (21% versus 68%; P < 0.001). At diagnosis, serum aTTG level was consistently lower in group 1 compared with group 2 (367 IU⁄mL versus 834 IU⁄mL; P = 0.030). Both groups reported symptom improvement at six months and one year. At the end of one year, aTTG level was more likely to be normal in group 1 compared with group 2 (64% versus 29%; P < 0.001).

CONCLUSION

Although they represent a minority group, South Asian children comprised a significant proportion of CD patients presenting to a Canadian celiac clinic. South Asian children were more likely to present with growth concerns, which has important implications for timely diagnosis in this population. In addition, the apparent delay in normalization of aTTG levels suggests that careful follow-up and culturally focused education supports should be developed for South Asian children with CD.

Utility of saliva and hair follicles in donor selection for hematopoietic stem cell transplantation and chimerism monitoring

Selection of an HLA identical donor is a critical pre-requisite for successful hematopoietic stem cell transplantation (HSCT). Most transplant centers utilize blood as the most common source of DNA for HLA testing. However, obtaining blood through phlebotomy is often challenging in patients with conditions like severe leucopenia or hemophilia, pediatric and elderly patients. We have used a simple in-house protocol and shown that HLA genotypes obtained on DNA extracted from saliva or hair are concordant with blood and hence can be used for selection of donors for HSCT or organ transplantation. Similarly, for post-HSCT chimerism monitoring, non-availability of pre-transplant DNA samples poses a major limitation of reference STR fingerprints. This study shows that DNA obtained post-HSCT from hair follicles can be used to generate pre-transplant patient specific fingerprints while the STR profiles obtained in saliva samples cannot as these display a mixed state of chimerism.

Genomic evaluation of HLA-DR3+ haplotypes associated with type 1 diabetes

We have defined three sets of HLA-DR3(+) haplotypes that provide maximum risk of type 1 disease development in Indians: (1) a diverse array of B8-DR3 haplotypes, (2) A33-B58-DR3 haplotype, and (3) A2-B50-DR3 occurring most predominantly in this population. Further analysis has revealed extensive diversity in B8-DR3 haplotypes, particularly at the HLA-A locus, in contrast to the single fixed HLA-A1-B8-DR3 haplotype (generally referred to as AH8.1) reported in Caucasians. However, the classical AH8.1 haplotype was rare and differed from the Caucasian counterpart at multiple loci. In our study, HLA-A26-B8-DR3 (AH8.2) was the most common B8-DR3 haplotype constituting >50% of the total B8-DR3 haplotypes. Further, A2-B8-DR3 contributed the maximum risk (RR = 48.7) of type 1 diabetes, followed by A2-B50-DR3 (RR = 9.4), A33-B58-DR3 (RR = 6.6), A24-B8-DR3 (RR = 4.5), and A26-B8-DR3 (RR = 4.2). Despite several differences, the disease-associated haplotypes in Indian and Caucasian populations share a frozen DR3-DQ2 block, suggesting a common ancestor from which multiple haplotypes evolved independently.

Celiac disease: prevalence, diagnosis, pathogenesis and treatment

Celiac disease (CD) is one of the most common diseases, resulting from both environmental (gluten) and genetic factors [human leukocyte antigen (HLA) and non-HLA genes]. The prevalence of CD has been estimated to approximate 0.5%-1% in different parts of the world. However, the population with diabetes, autoimmune disorder or relatives of CD individuals have even higher risk for the development of CD, at least in part, because of shared HLA typing. Gliadin gains access to the basal surface of the epithelium, and interact directly with the immune system, via both trans- and para-cellular routes. From a diagnostic perspective, symptoms may be viewed as either "typical" or "atypical". In both positive serological screening results suggestive of CD, should lead to small bowel biopsy followed by a favourable clinical and serological response to the gluten-free diet (GFD) to confirm the diagnosis. Positive anti-tissue transglutaminase antibody or anti-endomysial antibody during the clinical course helps to confirm the diagnosis of CD because of their over 99% specificities when small bowel villous atrophy is present on biopsy. Currently, the only treatment available for CD individuals is a strict life-long GFD. A greater understanding of the pathogenesis of CD allows alternative future CD treatments to hydrolyse toxic gliadin peptide, prevent toxic gliadin peptide absorption, blockage of selective deamidation of specific glutamine residues by tissue, restore immune tolerance towards gluten, modulation of immune response to dietary gliadin, and restoration of intestinal architecture.

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.

Genetic correlates influencing immunopathogenesis of HIV infection

Variability to HIV infection, its progression as well as responsiveness to antiretroviral therapy (ART) is observed among individuals including viraemia controllers or exposed uninfected, rapid versus slow progressors and ART responders compared to non responders. This differential responsiveness/vulnerability to HIV-1 is governed by multiple host genetic factors that include HLA, cytokines, chemokines, their receptors and others. This review highlights the influence of these genetic factors on HIV/AIDS outcome; however, in India, the information in this area is very limited and most of these genetic studies have been conducted in Caucasian and South African populations. Considering, the population specific differences in the frequencies of protective or susceptibility favouring alleles and their influence on the disease outcome, it is of utmost importance to strengthen ongoing efforts towards defining largely unknown genetic propensity in Indian population, particularly by recruitment of large cohorts of well categorized exposed uninfected individuals, rapid, long term non progressors and elite viraemic controllers. Multi-parametric analysis of these potentially interactive immunogenetic variables in these cohorts may help to define potential targets for diagnostics and therapy in a population specific manner.

Tumor necrosis factor-associated susceptibility to type 1 diabetes is caused by linkage disequilibrium with HLA-DR3 haplotypes

Tumor necrosis factor-α (TNF-α) is an important proinflammatory cytokine involved in the pathogenesis of autoimmune type 1 diabetes (T1D). The TNF gene locus is located in the major histocompatibility complex (MHC) class III region and its genetic polymorphisms have been reported to be associated with T1D. However, it is not clear whether these associations are primary or caused by their linkage disequilibrium with other predisposing genes within the MHC. We have tested 2 TNF-α single nucleotide polymorphisms at positions -308G/A and -238G/A in the 5' untranslated region and a (GT)n microsatellite TNFa in the North Indian healthy population and T1D patients with known HLA-A-B-DR-DQ haplotypes. The allele frequencies of TNFa5, -308A, and -238G were determined to be significantly increased among patients compared with controls. Although the observed positive association of -238G was caused by its presence on all 3 DR3(+) groups, namely, B8-DR3-DQ2, B50-DR3-DQ2, and B58-DR3-DQ2 haplotypes associated with T1D in this population, the increase of the -308A allele was caused by its association with the latter 2 haplotypes. On the other hand, TNF -308G occurred on B8-DR3 haplotypes along with -238G and TNFa5 alleles, particularly in T1D patients with late disease onset (at >20 years of age). These results indicate that TNF associations with T1D are caused by their linkage disequilibrium with specific HLA-DR3-DQ2 haplotypes in the Indian population. Because polymorphisms in the promoter region regulate TNF expression levels (e.g., -308A), they retain crucial immunological significance in the development of T1D and its management.

European Society for Pediatric Gastroenterology, Hepatology, and Nutrition guidelines for the diagnosis of coeliac disease

OBJECTIVE

Diagnostic criteria for coeliac disease (CD) from the European Society for Paediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) were published in 1990. Since then, the autoantigen in CD, tissue transglutaminase, has been identified; the perception of CD has changed from that of a rather uncommon enteropathy to a common multiorgan disease strongly dependent on the haplotypes human leukocyte antigen (HLA)-DQ2 and HLA-DQ8; and CD-specific antibody tests have improved.

METHODS

A panel of 17 experts defined CD and developed new diagnostic criteria based on the Delphi process. Two groups of patients were defined with different diagnostic approaches to diagnose CD: children with symptoms suggestive of CD (group 1) and asymptomatic children at increased risk for CD (group 2). The 2004 National Institutes of Health/Agency for Healthcare Research and Quality report and a systematic literature search on antibody tests for CD in paediatric patients covering the years 2004 to 2009 was the basis for the evidence-based recommendations on CD-specific antibody testing.

RESULTS

In group 1, the diagnosis of CD is based on symptoms, positive serology, and histology that is consistent with CD. If immunoglobulin A anti-tissue transglutaminase type 2 antibody titers are high (>10 times the upper limit of normal), then the option is to diagnose CD without duodenal biopsies by applying a strict protocol with further laboratory tests. In group 2, the diagnosis of CD is based on positive serology and histology. HLA-DQ2 and HLA-DQ8 testing is valuable because CD is unlikely if both haplotypes are negative.

CONCLUSIONS

The aim of the new guidelines was to achieve a high diagnostic accuracy and to reduce the burden for patients and their families. The performance of these guidelines in clinical practice should be evaluated prospectively.

Prevalence of celiac disease in the northern part of India: a community based study

BACKGROUND AND AIM

While celiac disease is estimated to affect about 1% of the world's population, it is thought to be uncommon not only in India but in Asia also. There is a lack of studies on the prevalence of celiac disease from Asian nations. The aim of the present study was to estimate the prevalence of celiac disease in the community.

METHODS

In a cross sectional study, we estimated the prevalence of celiac disease in urban and rural populations in the National Capital Region, Delhi, India. A structured questionnaire was administered, by door-to-door visits, to all participants to collect socio-demographic data and to screen for features of celiac disease, namely chronic or recurrent diarrhea and, anemia. In children, additional features, namely short stature (linear height below 5th percentile for age) and failure to thrive/gain weight were also used. All respondents who were screen positive (any one of above) and 10% of screen negative individuals were called for serological testing, which is anti-tissue transglutaminase antibody. All serologically positive respondents were invited to undergo further evaluation including endoscopic biopsy. Celiac disease was diagnosed on the basis of a positive serology, the presence of villous atrophy and/or response to gluten free diet.

RESULT

Among 12,573 contacted, 10,488 (83.4%) (50.6% male) agreed to participate. Based on screening, 5622 (53.6%) participants were screen positive. Of all those screen positive, 2167 (38.5%) agreed for serological testing; additionally 712 (14%) negatives were also tested. The overall sero-prevalence of celiac disease was 1.44% (95% confidence interval [CI] 1.22 1.69) and the overall prevalence of celiac disease was 1.04% (95% CI 0.85 1.25).

CONCLUSION

The prevalence of celiac disease in this north Indian community is 1 in 96. Celiac disease is more common than is recognized in India.

Frequency of HLA-DQA1*0501 and DQB1*0201 alleles in patients with coeliac disease, their first-degree relatives and controls in Jordan

BACKGROUND

The primary genetic marker associated with coeliac disease (CD) is the HLA-DQ2 molecule, encoded by the DQA1*0501 and DQB1*0201 genes.

AIM

To investigate the frequency of HLA-DQA1*0501 and DQB1*0201 alleles in Jordanian patients with CD and their first-degree relatives.

METHODS

An allele-specific DNA-based PCR-sequence-specific primer was used to investigate DQA1*0501 and DQB1*0201 alleles in 44 CD patients, 47 first-degree relatives and 53 healthy controls.

RESULTS

The mean age of the patients at the time of diagnosis was 13.5 years (range 1-39) and at the time of the study was 19.3 years (range 5-42). The DQA1/B1 (0501; 0201) haplotype was present in 80% of patients and 66% of first-degree relatives compared with 32% of controls (p<0.0001 and <0.01, respectively). The remaining 20% of CD patients who were negative for the DQ2 molecule carried the DQB1*0201 allele only. A statistically significant difference was detected in the DQ2 hetero-dimer frequency between CD patients, their first-degree relatives and controls with a higher frequency in the patients group (p<0.001).

CONCLUSION

The significant differences in the frequency of DQA1*0501, DQB1*0201 alleles in CD patients and their first-degree relatives compared with the control group demonstrated the important role of these alleles in the development of CD in the Jordanian population.

Coeliac disease in a child with anorectal malformation: The importance of considering other causes of diarrhea

We present the case of an Indian child with a high anorectal malformation (ARM) who postoperatively had troublesome fecal incontinence. Based on a dietary history, weight loss, and diarrhea, a duodenal biopsy was performed that revealed coeliac disease. Since being on a gluten-free diet, her symptoms have improved dramatically. To the best of our knowledge this is the first report in the English literature of such an association between ARMs and coeliac disease. Dietary modification alone can dramatically improve symptoms in these children.

The response to hepatitis B vaccine: does it differ in celiac disease?

OBJECTIVES

There is a relationship between nonresponsiveness to hepatitis B virus (HBV) vaccine and certain human leukocyte antigen (HLA) genotypes. In healthy population, 4-10% vaccine recipients fail to produce protective levels of antibodies to the HBV vaccine after standard immunization depending upon age and the presence of various underlying diseases. Celiac disease (CD) is an HLA-associated immunological disease. It has been suggested that certain HLA haplotypes which are linked to CD are associated with nonresponse to HBV vaccine as well. The aim of this study is to assess the response to HBV vaccine prospectively in a group of CD and to explore the potential link between CD and HBV vaccine nonresponse by studying shared HLA haplotypes.

PATIENTS AND METHODS

Sixty-three previously diagnosed celiac patients who were on a strict gluten-free diet (GFD) and 54 healthy children were evaluated serologically for anti-HBs status. Celiac children who were anti-HBs negative at baseline were fully vaccinated prospectively, and reevaluated for the response to HBV vaccine. To estimate the role of HLA type in HBV vaccine response in celiac patients, a subgroup of both patients and control participants had HLA genotypes performed.

RESULTS

At enrollment, 27 (67.5%) children with CD and 48 (85.2%) healthy children were anti-HBs positive, and the difference between patients and controls was statistically significant (P<0.05). However, failure to respond to HBV vaccine was only 3.6% (response rate 96.4%) in prospectively vaccinated celiac patients. There was no relationship between HLA type and vaccine nonresponse in our study group.

CONCLUSION

The response to HBV vaccine in celiac children who were compliant to GFD is not different from a healthy population. CD may be one of the immune diseases associated with a high rate of HBV vaccine nonresponse but it might not be permanent and treatment with GFD and compliance to the treatment may ameliorate the immune response to HBV vaccine in celiac children.

Compound KIR-HLA genotype analyses in the Iranian population by a novel PCR-SSP assay

Natural killer (NK) cells eliminate infected and transformed cells while still are self-tolerant. Interactions of the independently segregating Killer cell immunoglobulin-like receptors (KIR) and human leucocyte antigens (HLA) loci play a critical role in NK cell regulation. Different compound KIR-HLA genotypes can impart different thresholds of activation to the NK-cell repertoire and such genotypic variation has been found to confer altered risk in a number of human diseases including viral infections, autoimmune disorders, reproduction abnormalities and cancers. In this study, we presented a novel combined KIR-HLA polymerase chain reaction-sequence-specific primers genotyping assay for simultaneous determination of KIR genes and their three major HLA class I ligand groups (C1, C2, and Bw4). Moreover, known inhibitory and activating KIR + HLA (iKIR + HLA: 2DL2/3 + C1, 2DL1 + C2, 3DL1 + Bw4; and aKIR + HLA: 2DS2 + C1, 2DS1 + C2, 3DS1 + Bw4) combinations as well as co-inheritance of aKIR genes and iKIR + HLA pairs were analysed in a total of 200 unrelated healthy Iranian individuals. All tested subjects had at least one of the three iKIR + HLA pairs and the frequencies of various inhibitory combinations in the study group were: 31.5%, three iKIR + HLA pairs, 53.5%, two iKIR + HLA pairs, and 15%, 0ne iKIR + HLA pair. Furthermore, we revealed that majority of Iranians (69%) carry compound genotypes with greater number of inhibitory pairings than activating combinations (iKIR + HLA > aKIR + HLA). Conversely, iKIR + HLA < aKIR (45%) was dominant genotype in the study group. We conclude that selective evolutionary pressure has propensity to maintain KIR-HLA genotypes with more inhibitory combinations to guarantee self-tolerance. In contrast, existence of activating KIR genes without normal endogenous ligands, potentially arms the NK population for competent immunosurveillance and stronger defense against infections.

Prevalence, human leukocyte antigen typing and strategy for screening among Asian first-degree relatives of children with celiac disease

BACKGROUND AND AIM

Data on prevalence, human leukocyte antigen (HLA) typing and small bowel histology among first-degree relatives of subjects with celiac disease (CD) is scarce. This prospective study evaluated the prevalence and role of HLA DQ2/8 testing in screening of first-degree relatives of children with CD.

METHODS

Thirty confirmed children with CD and 91/94 first-degree relatives (parents and siblings) were enrolled. HLA DQ2/8 testing was carried out in all index CD cases. Clinical evaluation with a questionnaire, total serum immunoglobulin A (IgA), human IgA-tissue transglutaminase (IgA-tTGA) and HLA DQ2/8 testing was carried out in all first-degree relatives. Subjects who were positive for IgA-tTGA were recommended endoscopic duodenal biopsy to document histological changes of CD.

RESULTS

Nine first-degree relatives were positive for IgA-tTGA, seven underwent duodenal biopsy and four subjects had Marsh IIIa changes suggestive of CD. The prevalence of histologically confirmed CD in first-degree relatives was 4.4%. The prevalence of potential CD was 9.8%. IgA-tTGA-positive subjects (4/9) were significantly more often symptomatic than IgA-tTGA-negative first-degree relatives (2/82). Twenty-nine (96.6%) index cases of CD and all IgA-tTGA-positive first-degree relatives were positive for HLA DQ2. None of the index CD cases or first-degree relatives were HLA DQ8-positive. A total of 85% of the first-degree relatives were positive for HLA DQ2 and thus at risk of developing CD.

CONCLUSIONS

In this first Asian study on a limited number of families of children with CD, 4.4% of the first-degree relatives had CD. Only 15% of the first-degree relatives were negative for HLA DQ2/DQ8. Initial evaluation with HLA and serology followed by only serial serology in HLA-positive relatives is recommended.

Indian task force for celiac disease: Current status

There are limited data on celiac disease (CD) from India. The limited knowledge about CD in India might be attributed to several factors. The first meeting of the Indian Task Force for Celiac Disease was held in the Asian Institute of Gastroenterology, Hyderabad, India in December 2008. The objectives of the meeting were to focus research on prevalence of CD in the wheat-eating Northern vs the rice-eating Southern Indian population, low-budget serological assays to study the underprivileged population, to involve other medical subspecialties in CD, to suggest proper legislation regarding wheat food labeling, and to organize affordable food substitutes for patients with celiac disease.

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.

Prevalence of celiac disease in the Asia-Pacific region

The development of sensitive and specific serological assays for celiac disease has led to a revision of the prevalence of this disease in many countries. In the Asia-Pacific region, prevalence has been determined in only a minority of countries but those with prevalence rates of 1:50-1:500 adults include Australia, Iran, Israel, New Zealand, Syria and Turkey. In contrast, celiac disease appears to be extremely rare in Japan and may be rare in China. In India, prevalence rates are high in the northern states but much lower in the southern states. In individual countries, important determinants of prevalence include the per capita consumption of wheat and the frequency of a specific human leukocyte antigen (HLA) type genetically defined as HLA-DQB1*02 (*0201 or *0202) and serologically defined as HLA-DQ2. These determinants predict low prevalence rates for celiac disease in the Pacific Islands, South-East Asia and eastern China but higher rates in countries west of India and China. There is also the potential for a rising incidence of celiac disease if traditional rice-based diets are replaced by Western-style diets with a higher content of wheat products.

HLA and autoimmune digestive disease: a clinically oriented review for gastroenterologists

OBJECTIVES

The human leukocyte antigen (HLA) system includes genes involved in graft-vs-host rejection and in immune response. The discovery that HLAs are associated with several diseases led to appealing developments both in basic biomedical research and in clinical medicine, and offered the opportunity to improve the understanding of pathogenesis and classification of diseases, as well as to provide diagnostic and prognostic indicators. The aim of this article is to review the association between HLA alleles and autoimmune digestive disease and its current relationship with modern HLA nomenclature and clinical practice.

METHODS

Articles dealing with the association between HLAs and autoimmune digestive disease (including celiac disease, inflammatory bowel disease, autoimmune hepatitis, sclerosing cholangitis and primary biliary cirrhosis) were searched for using Pubmed and SCOPUS databases from earliest records to January 2008.

RESULTS

The review has provided two sections. In the first, we explain the basic principles of HLA structure, function, and nomenclature, as an introduction to the second section, which describes current associations between HLA alleles and digestive diseases. The clinical implications of each HLA association are critically discussed. Actually, a clinical role for HLA typing is suggested for only a few conditions, e.g., celiac disease.

CONCLUSIONS

The knowledge of current HLA nomenclature and of its association with some digestive diseases such as celiac disease can be useful in clinical practice for diagnostic and prognostic purposes. This can avoid improper HLA typing as well as stressing the need for further studies on other possible clinical applications.

Immunogenetic basis of HIV-1 infection, transmission and disease progression

Susceptibility to HIV-1 infection and rate of disease progression to AIDS are complex traits modulated by environmental and genetic factors. Studies on large AIDS cohorts and their meta-analyses have identified numerous AIDS restriction genes that regulate HIV cell entry (particularly chemokine co-receptors and their ligands), acquired and innate immunity (major histocompatibility complex (MHC), killer immunoglobulin-like receptors (KIRs), and cytokines) and others that influence outcome of HIV infection. However, vast inter-individual variability is often observed and some rare individuals like 'long-term non-progressors (LTNPs) or exposed uninfected' (EUs) appear to be protected due to natural resistance. A better understanding of genetic basis of such a 'natural resistance' to infection would bear important implications in designing therapeutic vaccine designs. The genetic variants that could limit AIDS vary in different populations. We have studied genetic variations in the MHC, cytokines and CCR2-CCR5 loci in the Asian-Indian HIV-infected population and compared with other global populations.

Celiac disease in the developing countries: A new and challenging public health problem

In the past, celiac disease was believed to be a chronic enteropathy, almost exclusively affecting people of European origin. The availability of new, simple, very sensitive and specific serological tests (anti-gliadin, anti-endomysium and anti-transglutaminase antibody assays) have shown that celiac disease is common not only in Europe and in people of European ancestry but also in the developing countries where the major staple diet is wheat (Southern Asia, the Middle East, North West and East Africa, South America), both in the general population and in the groups at risk. Gluten intolerance thus appears to be a widespread public health problem and an increased level of awareness and clinical suspicion are needed in the New World where physicians must learn to recognize the variable clinical presentations (classical, atypical and silent forms) of celiac disease. In the developing countries, both serological screening in the general population and serological testing in groups at risk are necessary for an early identification of celiac patients. The gluten-free diet poses a challenging public health problem in the developing countries, especially since commercial gluten-free products are not available.

Receptor-ligand analyses define minimal killer cell Ig-like receptor (KIR) in humans

Interactions between inhibitory killer cell immunoglobulin-like receptors (iKIR) and human leukocyte antigen (HLA) class I molecules regulate natural killer (NK) cell responses to eliminate infected and transformed cells while maintaining tolerance to healthy cells. Unlinked polymorphic gene families encode KIR receptors and HLA class I ligands and their independent segregation results in a variable number and type of iKIR + HLA pairs inherited in individuals. The diversity in the co-inheritance of iKIR + HLA pairs and activating KIR (aKIR) genes in 759 unrelated individuals from four ethnic populations was analyzed. Every individual studied inherited a minimum of one iKIR + HLA pair; suggesting that major histocompatibility complex class I-dependent inhibitory KIR signaling is essential for human NK cell function. In contrast, 13.4% of the study group lacked all aKIR genes. Twenty percent of the study group carried only one of the four iKIR + HLA pairs. Interestingly, 3% of the study group carrying only KIR2DL3 + HLA-C1 as an iKIR + HLA pair lacked aKIR genes. These data suggest that a single iKIR can constitute the minimal KIR repertoire for human NK cells. Genotypes carrying an equal number of iKIR + HLA pairs and aKIR genes represented 20% of the study group. The remaining individuals had either a dominant inhibitory KIR genotype (iKIR + HLA > aKIR) or a dominant activating KIR genotype (iKIR + HLA < aKIR). Genotypes encoding these imbalanced inhibitory and activating interactions may contribute to susceptibility or resistance to human diseases.

Diagnostic significance of HLA-DQ typing in patients with previous coeliac disease diagnosis based on histology alone

BACKGROUND

Coeliac disease is strongly associated with human leukocyte antigen (HLA)-DQ2 or DQ8 genotypes. The diagnosis is based on demonstrating crypt-hyperplastic villous atrophy, endomysial or transglutaminase antibodies and correlation of disease activity with gluten intake.

AIM

To evaluate the clinical utility of HLA-DQ typing, when coeliac disease diagnosis had previously been established solely by histology.

METHODS

HLA-DQ alleles, endomysial and transglutaminase antibodies were investigated and histology slides reviewed in 70 patients diagnosed 2-25 years earlier by small-intestinal biopsy but without measuring endomysial or transglutaminase antibodies. Patients without DQ2 or DQ8 or without unequivocal villous atrophy were followed-up on free diet by using serology and biopsies.

RESULTS

All 40 endomysial/transglutaminase antibodies positive patients carried DQ2 or DQ8, and 39 of them had severe villous atrophy. Only 56% of patients without endomysial or transglutaminase antibodies positivity had DQ2 or DQ8 (P < 0.001). Seropositivity and relapse developed in 4 of 11 DQ2 positive but in none of 15 DQ2 and DQ8 negative patients on long-term gluten exposure.

CONCLUSIONS

Coeliac disease diagnosis based solely on histology is not always reliable. HLA-DQ typing is important in identifying DQ2 and DQ8 negative subjects who need revision of their diagnosis, but it does not have additive diagnostic value if endomysial positivity is already known.