HLA haplotypes associated with type 1 diabetes mellitus in North Indian children

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.

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.

Segregation Analysis of Genotyped and Family-Phased, Long Range MHC Classical Class I and Class II Haplotypes in 5 Families With Type 1 Diabetes Proband in the United Arab Emirates

The classical Human Leucocyte Antigen (HLA) class II haplotypes of the Major Histocompatibility Complex (MHC) that are associated with type 1 diabetes (T1D) were identified in five families from the United Arab Emirates (UAE). Segregation analyses were performed on these 5 families with the disease, 3 with one child and 2 with 2 children diagnosed with T1D. Three HLA-DR4 haplotypes were identified: HLA- DRB1^∗04:01:01-DQB1^∗03:02:01:01; HLA- DRB1^∗04:02:01- DQB1^∗03:02:01; and HLA -DRB1^∗04:05:01-DQB1^∗02:02:01:02. All have previously been identified to be associated with T1D in studies of the Arabian population. In the 10 parents from the 5 families, 9 had at least one HLA-DR4 and HLA-DR3 haplotype which potentially increases the risk of T1D. Of these 9 parents, 3 were heterozygous for HLA-DR4/HLA-DR3 and one was homozygous for HLA-DR3. Two haplotypes that were identified here extend to the HLA class I region were previously designated AH8.2 (HLA -A^∗26-B^∗08-DRB1^∗03) and AH50.2 (HLA -C^∗06-B^∗50-DRB1^∗03:01-DQ^∗02) and associated with diabetes in neighboring North Indian populations. This study provides examples of MHC haplotype analysis in pedigrees to improve our understanding of the genetics of T1D in the understudied population of the UAE.

Differential HLA Association of GAD65 and IA2 Autoantibodies in North Indian Type 1 Diabetes Patients

The human leucocyte antigen (HLA) association with type 1 diabetes (T1D) is well known but there are limited studies investigating the association between β-cell autoantibodies and HLA genes. We evaluated the prevalence of GAD65 and IA-2 autoantibodies (GADA and IA2A) in 252 T1D patients from North India and investigated the genetic association of GADA and IA2A with HLA class I and class II genes/haplotypes. GADA and IA2A were detected in 50.79% and 15.87% of T1D patients, respectively, while only 8.73% had both GADA and IA2A. HLA-DRB1^∗03 was observed to be significantly higher in GADA+ T1D patients as compared to GADA- (91.41% vs. 66.13%, Bonferroni-corrected P (P _c) = 1.11 × 10^-5; OR = 5.45; 95% CI: 2.67-11.08). Similarly, HLA-DQB1^∗02 was found to be significantly increased in GADA+ patients (94.53%, P _c = 2.19 × 10^-5; OR = 6.27; 95% CI: 2.7-14.49) as compared to GADA- (73.39%). The frequencies of HLA-DRB1^∗04 and DQB1^∗03 were increased in IA2A+ patients (45.0% and 52.5%, respectively) as compared to that in IA2A- (25.94% and 33.96%, respectively). Further, the frequency of DRB1^∗03-DQB1^∗02 haplotype was found to be significantly increased in GADA+ T1D patients as compared to GADA- (60.55% vs. 41.94%, P = 3.94 × 10^-5; OR = 2.13; 95%CI = 1.49-3.03). Similarly, HLA-DRB1^∗04-DQB1^∗03 haplotype was found to be significantly increased in IA2A+ T1D patients compared to IA2A- patients (22.5% vs. 12.97%; P = 0.041; OR = 1.95; 95%CI = 1.08-3.52). None of the HLA class I genes (HLA-A, B, and Cw) was found to be associated with GADA or IA2A in people with T1D. Our findings suggest that HLA-DRB1^∗03/DQB1^∗02 and HLA-DRB1^∗04/DQB1^∗03 might play an important role in the development of GADA and IA2A, respectively.

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.

Diverse human leukocyte antigen association of type 1 diabetes in north India

BACKGROUND

Type 1 diabetes (T1D) is a complex disease, with involvement of various susceptibility genes. Human leukocyte antigen (HLA) on chromosome 6p21 is major susceptibility region. This study examined genetic association of HLA genes with T1D.

METHODS

The study recruited 259 T1D patients and 706 controls from north India. PCR-SSP and LiPA were used to type HLA Class I and II alleles.

RESULTS

At HLA Class I locus, HLA-A*02, A*26, B*08 and B*50 were significantly increased in patients vs controls (39.8% vs 28.9% [Bonferroni-corrected P {P_c } = 0.032], 24.7% vs 9.6% [P_c  = 4.83 × 10^-8 ], 37.2% vs 15.7% [P_c  = 1.92 × 10^-9 ], and 19.4% vs 5.5% [P_c  = 4.62 × 10^-9 ], respectively). Similarly, in Class II region, DRB1*03 showed a strong positive association with T1D (78.7% vs 17.5% in controls; P = 1.02 × 10^-9 ). Association of DRB1*04 with T1D (28.3% vs 15.5% in controls; P_c  = 3.86 × 10^-4 ) was not independent of DRB1*03. Negative associations were found between T1D and DRB1*07, *11, *13, and *15 (13.8% vs 26.1% in controls [P_c  = 0.00175], 3.9% vs 16.9% in controls [P_c  = 6.55× 10^-6 ], 5.5% vs 21.6% in controls [P_c  = 2.51 × 10^-7 ], and 16.9% vs 43.9% in controls [P_c  = 9.94× 10^-10 ], respectively). Compared with controls, patients had significantly higher haplotype frequencies of A*26-B*08-DRB1*03-DQA1*05-DQB1*02 (10.43% vs 1.96%; P = 7.62 × 10^-11 ), A*02-B*50-DRB1*03-DQA1*05-DQB1*02 (6.1% vs 0.71%; P = 2.19 × 10^-10 ), A*24-B*08-DRB1*03-DQA1*05-DQB1*02 (4.72% vs 0.8%; P = 5.4 × 10^-7 ), A*02-B*08-DRB1*03-DQA1*05-DQB1*02 (2.36% vs 0.18%; P = 3.6 × 10^-5 ), and A*33-B*58-DRB1*03-DQA1*05-DQB1*02 (4.33% vs 1.25%; P = 0.00019).

CONCLUSIONS

In north India, T1D is independently associated only with HLA-DRB1*03 haplotypes, and is negatively associated with DRB1*07, *11, *13, and *15.

Diabetes in South Asians: Phenotype, Clinical Presentation, and Natural History

PURPOSE OF REVIEW

South Asia is one of the epicenters of the global diabetes pandemic. Diabetes in south Asians has certain peculiar features with respect to its pathophysiology, clinical presentation, and management. This review aims to summarize some of the recent evidence pertaining to the distinct diabetes phenotype in south Asians.

RECENT FINDINGS

South Asia has high incidence and prevalence rates of diabetes. The progression from "pre-diabetes" to diabetes also occurs faster in this population. Pancreatic beta cell dysfunction seems to be as important as insulin resistance in the pathophysiology of diabetes in south Asians. Recent evidence suggests that the epidemic of diabetes in south Asia is spreading to rural areas and to less affluent sections of society. Diabetes in south Asians differs significantly from that in white Caucasians, with important implications for prevention, diagnosis, and management.

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.

Diabetes mellitus and its complications in India

India is one of the epicentres of the global diabetes mellitus pandemic. Rapid socioeconomic development and demographic changes, along with increased susceptibility for Indian individuals, have led to the explosive increase in the prevalence of diabetes mellitus in India over the past four decades. Type 2 diabetes mellitus in Asian Indian people is characterized by a young age of onset and occurrence at low levels of BMI. Available data also suggest that the susceptibility of Asian Indian people to the complications of diabetes mellitus differs from that of white populations. Management of this disease in India faces multiple challenges, such as low levels of awareness, paucity of trained medical and paramedical staff and unaffordability of medications and services. Novel interventions using readily available resources and technology promise to revolutionise the care of patients with diabetes mellitus in India. As many of these challenges are common to most developing countries of the world, the lessons learnt from India's experience with diabetes mellitus are likely to be of immense global relevance. In this Review, we discuss the epidemiology of diabetes mellitus and its complications in India and outline the advances made in the country to ensure adequate care. We make specific references to novel, cost-effective interventions, which might be of relevance to other low-income and middle-income countries of the world.

Family-based association study of HLA class II with type 1 diabetes in Moroccans

BACKGROUND

The T1D is a multifactorial disease; with a strong genetic control. The human leukocyte antigen (HLA) system plays a crucial role in the autoimmune process leading to childhood diabetes. About 440,000 of the childhood population of the world (1.8 billion children under 14 years of age), have type 1 diabetes, and each year an additional 70,000 develop this disorder. The objective of this study was to investigate the distribution of HLA class II in Moroccan families of diabetic children to identify susceptibility alleles of the Moroccan population.

SUBJECTS AND METHODS

We included in this study, Moroccan families who have at least one child with T1D. The age of onset of diabetes was less than 15 years. HLA class II (DRB1* and DQB1*) was carried out by molecular biology techniques (PCR-SSP and PCR-SSO). The FBAT test (family-based association test) was used to highlight the association between T1D and the HLA-DRB1* and -DQB1* polymorphism.

RESULTS

The association of HLA class II (DRB1*, DQB1*) in type 1 diabetes was analyzed in fifty-one Moroccan families, including 90 diabetics. The results revealed that the most susceptible haplotypes are the DRB1*03:01-DQB1*02:01, DRB1*04:05-DQB1*03:02 (Z=3.674, P=0.000239; Z=2.828, P=0.004678, respectively). And the most protective haplotype is the DRB1*15-DQB1*06.

CONCLUSION

This is the first family-based association study searching for an association between HLA class II and T1D in a Moroccan population. Despite the different ethnic groups forming Morocco, Moroccan diabetics share the most susceptible and protective HLA haplotypes with other Caucasians populations, specifically the European and Mediterranean populations.

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.

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.

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.

Clinical profile of coexisting conditions in type 1 diabetes mellitus patients

AIMS

Type 1 diabetes mellitus (T1DM) is associated with various genetic and autoimmune diseases implicated in its etiopathogenesis. We hereby profile the clinical association of such diseases among patients from our center.

METHODS

Consecutive patients of T1DM presenting to department of Endocrinology from May 1997 to December 2011 were retrospectively analyzed in context of associated clinical profile.

RESULTS

Among 260 patients diagnosed as T1DM, 21 (8%) had hypothyroidism, 4 (1.5%) had hyperthyroidism and 2 (0.7%) had primary adrenal insufficiency. Eighteen patients (7%) had celiac disease, 9 (3.5%) had Turner's syndrome, 5 patients (1.9%) had Klinefelter's syndrome, whereas Down's syndrome and Noonan's syndrome was present in 2 and 1 patients (0.7%) respectively. One patient had Wolframs' syndrome and 1 patients had myasthenia gravis. Systemic lupus erythematosus and rheumatoid arthritis were present in 3 and 1 patients respectively. Total of 5 patients with cerebral palsy, 4 cases with deaf mutism, 4 cases with acute psychosis and 16 patients with depression were noted. Mean age of study patients was 20.8±9.8 years (range, 3-23 years).

CONCLUSION

Various conditions including genetic (Down, Turner, Noonan, and Klinefelter's), autoimmune (thyroid and adrenal disorders, myasthenia gravis, SLE, rheumatoid arthritis) and central nervous system diseases were the associated diseases encountered in our patients. Routine screening is required for early diagnosis and treatment of associated co morbidities.

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.

Approaches in type 1 diabetes research: A status report

Type 1 diabetes is a multifactorial disease with an early age of onset, in which the insulin producing beta cell of the pancreas are destroyed because of autoimmunity. It is the second most common chronic disease in children and account for 5% to 10% of all diagnosed cases of diabetes. India is having an incidence of 10.6 cases/year/100,000, and recent studies indicate that the prevalence of type 1 diabetes in India is increasing. However in view of poor health care network, there is no monitoring system in the country. Of the 18 genomic intervals implicated for the risk to develop type 1 diabetes, the major histocompatibility complex (MHC) region on chromosome 6p21.31 has been the major contributor estimated to account for 40-50%, followed by 10% frequency of INS-VNTR at 5' flanking region of the insulin gene on chromosome 11p15.5. However, population studies suggest that > 95% of type 1 diabetes have HLA-DR3 or DR4, or both, and in family studies, sibling pairs affected with type 1 diabetes have a non-random distribution of shared HLA haplotypes. As predisposing genetic factors such as HLA alleles are known, immunological interventions to prevent type 1 diabetes are of great interest. In the present study we have reviewed the status of molecular genetics of the disease and the approaches that need to be adopted in terms of developing patient and suitable control cohorts in the country.

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.

Genetic determinants of Type 1 diabetes: immune response genes

Type 1 diabetes (T1D) is a polygenic autoimmune disease. Susceptibility to T1D is strongly linked to a major genetic locus that is the MHC, and several other minor loci including insulin, cytotoxic T-lymphocyte-associated antigen-4, PTPN22 and others that contribute to diabetes risk in an epistatic way. We have observed that there are three sets of DR3-positive autoimmunity-favoring haplotypes in the north-Indian population, including B50-DR3, B58-DR3 and B8-DR3. The classical Caucasian autoimmunity favoring AH8.1 (HLA-A1-B8-DR3) is rare in the Indian population, and has been replaced by a variant AH8.1v, which differs from the Caucasian AH8.1 at several gene loci. Similarly, there are additional HLA-DR3 haplotypes, A26-B8-DR3 (AH8.2), A24-B8-DR3 (AH8.3), A3-B8-DR3 (AH8.4) and A31-B8-DR3 (AH8.5), of which AH8.2 is the most common. The fact that disease-associated DR3-positive haplotypes show heterogeneity in different populations suggests that these might possess certain shared components that are involved in the development of autoimmunity.

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.

Asian Indian donor marrow registry: All India Institute of Medical Sciences experience

A major limitation in hematopoietic stem cell transplantation (HSCT) is the availability of a genetically matched donor, particularly with respect to the human leukocyte antigens (HLA)-linked immune response genes located on chromosome 6 in humans. During the last 5 years, a total of 688 patients requiring HSCT underwent HLA testing in our department to identify a matched donor from their families. The sibship size ranged from 1 to > or =5 in all disease categories, except thalassemia major where the majority of patients had only 1 sibling. Family genotype analysis revealed that 39.3% of the total number of patients had an HLA-matched sibling and that families with sibship size of > or =4 had a higher probability (68.8%) compared with those with sibship size of < or =3 (29.7%). Because the Indian population is characterized by the presence of novel HLA alleles and unique haplotypes (HLA-A*0211, B*2707, A*26-B*08-DRB1*03), patients with rare HLA alleles have much less probability of finding an unrelated optimally matched donor than those with common HLA phenotypes. Smaller family size and unique HLA profile are limitations that can be overcome by developing unrelated volunteer marrow donor registries. The Asian Indian Donor Marrow Registry at our institute is regularly providing services to such patients.

Immunogenetic association and thyroid autoantibodies in juvenile autoimmune thyroiditis in North India

OBJECTIVES

Autoimmune thyroid diseases (AITD) encompass a number of conditions that have in common cellular and humoral responses targeting the thyroid gland. Interactions between susceptibility genes and environmental triggers are thought to initiate an autoimmune response to thyroid antigens leading to disease manifestation. Commencement of the disease in childhood leads to the presumption that genetics may have an important role in the causation of the disease.

DESIGN

The present study was aimed at evaluating the human leucocyte antigen (HLA) encoded susceptibility to develop juvenile autoimmune thyroiditis (JAT) in patients from North India.

PATIENTS

We studied 48 consecutive patients of JAT along with 176 first-degree relatives for their thyroid function (FT4, TSH) and anti-thyroid peroxidase antibody status (AbTPO).

MEASUREMENTS

HLA studies were carried out using serology for HLA-class I antigens and DNA analysis of HLA-class II alleles. The data were compared with a cohort of 308 ethnically matched healthy individuals.

RESULTS

We observed overt hypothyroidism in 50% and AbTPO positivity in 70.8% of the index cases. Among the first-degree relatives, goitre was observed in 51.7%, thyroid dysfunction in 28.4% and AbTPO in 29.5% of individuals. Of the 37 relatives who underwent fine-needle aspiration cytology (FNAC), 60% had evidence of chronic lymphocytic thyroiditis (CLT). A strong positive association of HLA-DRB1*1404 was observed with the JAT (35.4%vs. 10.4%, chi2 = 19.8, Pc = 0.0001). We also observed a higher (72%, P = 0.03) paternal transmission of HLA-DRB1*1404 to affected offspring in comparison to unaffected offspring. HLA-DRB1*03 was also increased among JAT patients but did not reach statistical significance.

CONCLUSION

These studies point towards an important role of immune modifying genes, such as HLA, in influencing susceptibility to juvenile-onset AITD.

Molecular basis of predisposition to develop type 1 diabetes mellitus in North Indians

Type 1 diabetes (T1D) mellitus is a multifactorial autoimmune disease where more than 90% of insulin-producing pancreatic beta cells are destroyed before the clinical manifestations, warranting a need to identify the children predisposed to get the disease. Of the 20 genomic intervals implicated for the risk to develop T1D, the major histocompatibility complex (MHC) region on chromosome 6p21.31 (IDDM1) has been the major contributor, followed by 5' regulatory region of the insulin (INS) gene on chromosome 11p15.5 (IDDM2). MHC has a role in antigen presentation and IDDM2 has been shown to have a role in transcription of insulin in the thymus. Hence, alleles of human leukocyte antigen (HLA)-DRB1, DQB1, and insulin-linked variable number of tandem repeats (INS-VNTR) were studied in 110 T1D patients and 112 healthy controls using polymerase chain reaction and hybridization with sequence-specific oligonucleotide probes (PCR-SSOP) and PCR restriction fragment length polymorphism (PCR-RFLP), respectively. HLA-DRB1*0301 was significantly increased in the T1D patients along with associated DQB1*0201 followed by DRB1*0401 and DRB1*0405. DRB1*0701 was observed to be the most protective allele followed by DRB1*0403 and DRB1*0404. Although DQB1*0302 which is associated with both the protective and susceptible DR4 alleles was not significantly increased, heterozygous DQB1*0201, *0302 was significantly increased in the TID patients. Because INS-VNTR class I homozygosity was also significantly increased in the patients, simultaneous presence of DRB1*0301 along with homozygous INS-VNTR class I, gave a relative risk (RR) of 70.81. However, a similar analysis of DQB1*0201 and *0302 along with INS-VNTR alleles did not give such high RRs. Thus, the two independently assorting alleles at two loci i.e., DRB1*0301 and INS-VNTR class I, on two different chromosomes may have the potential to predict a prediabetic in North India.