Evaluation and Identification of Celiac Disease Associated Antigen DQ2 and DQ8 in Northern Indian-Kashmir Valley

Introduction

Celiac disease (CD) also known as celiac sprue or gluten-sensitive enteropathy, is an immune modulated, chronic inflammatory disorder of the small bowel mucosa, which occurs in genetically predisposed individuals induced by the ingestion of gluten, the major storage protein of wheat and similar grains [1]. CD is now considered a relatively common disease worldwide and prevalence rate of approximately 1%, ranging from 0.71- 1.25% with female preponderance in early age group has been reported. Contrary to earlier thoughts of low prevalence rates among Indian population, recent evidence shows an increasing prevalence even in India, especially North India currently its prevalence rate is approximately 0.6-1% [2]. In celiac disease, exposure to gluten, in genetically predisposed individuals, leads to the development of immune reactions associated with the activation of CD4, CD8 lymphocytes, production of pro- inflammatory cytokines, excessive proliferation of intraepithelial lymphocytes, migration of macrophages to the intestinal wall and intestinal mucosa besides that there is induction of β lymphocytes, which produces specific antibodies to tissue transglutaminase 2 (tTG2), endomysia antibodies (EMA) and the delaminated form of gliadin peptides (DPG). This process leads to mucosal damage of the small bowel and other organs, producing symptoms ranging from malabsorption like diarrhoea, abdominal distension and weight loss, to nonspecific signs and symptoms such as fatigue, osteoporosis or iron deficiency anaemia [3]. The pathogenesis of CD involves interplay between genetic, epigenetic and immune factors. The major susceptibility genes in CD are the human leukocyte antigen (HLA)-DQ2 and HLA-DQ8, cluster which are necessary, but not sufficient to cause disease. The DQ genes account for approximately 40% of the genetic risk. Other genetic factors, including non-HLA genes that are involved in barrier and immune function, also contribute to disease susceptibility that accounts for a small proportion of the overall risk [4, 5]. Till date no study has been carried out to evaluate and identify the the HLA DQ2 and HLA DQ8 haplotypes in kashmiri population with cealic disease.

Materials and Methods

Blood samples of 67 subjects, including 25 males and 35 females with CD diagnosed on the basis of clinical symptoms, serological investigations and small-intestine biopsy were collected in the Department of Immunology and Molecular Medicine, Sher-I-Kashmir Institute of Medical Sciences (SKIMS), which serves as a tertiary care referral centre for patients with known, suspected or complicated CD.

Results

Reaction patterns revealed that among the sixty participants, seven (11.66%) were DQ2+/ DQ8+, thirty two (53.33%) were DQ2+/ DQ8-, five (8.33%) were DQ2- / DQ8+, and sixteen (26.66%) were DQ2-/ DQ8- (Figure 1).

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Figure1: Percentage distribution of different allele combinations.

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NAF=No allele found positive. Figure 2: Percentage distribution of susceptibility to celiac disease.

Results revealed that among the sixty participants, twelve (20%) participants have Low, fourteen (23.33%) participants have high, eighteen (30%) participants have very high and Sixteen (26.67%) participants have no susceptibility to celiac disease (Figure 2).

Results also revealed that among the twenty five male participants, five were DQ2+/ DQ8+, ten were DQ2+/ DQ8-, two were DQ2-/ DQ8+, and eight were DQ2-/ DQ8- pointing out that about 68% of the studied male participants were susceptible to celiac disease. Among the thirty five female participants, two were DQ2+/ DQ8+, twenty two were DQ2+/ DQ8-, three were DQ2-/ DQ8+, and eight were DQ2-/ DQ8- indicating that 76.53% of the studied female participants were susceptible to celiac disease (Figure 3).

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Figure3: Gender based percentage of celiac disease.

Discussion and Conclusion

The genetics of CD is known to involve a number of factors, HLA DQ2 and DQ8 genes being the most important that are responsible for up to 40% of the genetic heritability of [6, 7, 8, 9] more than 95% of celiac patients share the major histocompatibility complex II class human leukocyte antigen (HLA) DQ2 or DQ8 haplotype; patients negative for both types are unlikely to suffer from celiac disease [10]. The major genetic determinants are HLA-DQA1*05 and HLA-DQB1*02, which encode the DQ2 heterodimer. HLA-DQ2 (DQ2) is a serotype group within HLA-DQ (DQ) serotyping system. DQ8, the split antigen of the DQ3 broad antigen is encoded by an allele B1*0302 [6, 7, 8, 10].

To date, very few studies have potentially investigated the prevalence of celiac disease in population-based samples. The prevalence of CD in the Indian subcontinent is still not clear but is likely to be progressively increasing [11]. During the recent years, it has been reported that in wheat- consuming states such as Punjab, Haryana, Delhi, Rajasthan, Uttar Pradesh, Bihar and Madhya Pradesh, prevalence of CD in predominantly higher on an epidemiological basis [12] studies on occurrence of celiac disease in Uttar Pradesh as well as from Delhi have indicated its similarity with the European susceptibility patterns [13, 14]. The rising number of celiac disease cases in hospitalized patients has been reported from the Ludhiana over the last 10 years [15]. However, past studies indicate that there is difference in prevalence of celiac disease in the northern and southern part of India [11]. It is likely that celiac disease would be more common in North India [16]. Thus the regional difference of CD occurrence in India could be conceivably related to the genetic differences integrated with variation in staple diet pattern. However such reports from Jammu and Kashmir fall under grey area. Current study was conducted on the ethnic Kashmiri population and results of the current study revealed that among the participants, majority of individuals (73.33%) were susceptible to celiac disease.

Current study included both male and female participants. The results highlighted that among the male participants about 68% were having susceptibility to celiac disease (20% were DQ2+/ DQ8 +, 40% were DQ2+/ DQ8-, 8% were DQ2-/ DQ8+, and 32% were DQ2-/ DQ8-). Among the female participants 76.53% were having susceptibility to celiac disease(5.71% were DQ2+/ DQ8+, 62.86% were DQ2+/ DQ8-, 8.57% were DQ2-/ DQ8+, and 22.86% were DQ2-/ DQ8-). We found higher percentage of susceptibility in females compared to males. Our findings on gender based susceptibility are supported by many earlier studies which reported a higher proportion of females to be positive for celiac disease as compared to males [16, 17, 18].

In conclusion, current study indicated that majority of the individuals among studied participants were susceptible to celiac disease and remarkably females are more susceptible as compared to males. Finding of the recent work could possibly pave a way for better understanding of the prevalence of CD in Jammu and Kashmir. However, this is a preliminary study involving a limited number of samples, therefore further studies with larger sample size need to be carried out for further validation of the results.