HLA-G 14 bp deletion/insertion polymorphism in celiac disease

HLA-G 14bp Ins/Del Polymorphism in the 3'UTR Region and Acute Rejection in Kidney Transplant Recipients: An Updated Meta-Analysis

Background and Objectives: Acute kidney injury (AKI) affects the survival rate of kidney transplant organs and patients. Acute rejection (AR) due to AKI may lead to kidney transplantation failure. It is known that there is a relationship between human leukocyte antigen-G (HLA-G), which is involved in immune regulation, and AR in transplant patients. Moreover, 14-bp insertion/deletion polymorphism in the 3' untranslated region (UTR) region of the HLA-G gene is known to affect HLA-G expression. However, its relationship to AR is still controversial. The aim of this study was to investigate whether HLA-G 14-bp insertion/deletion polymorphism contributed to the development of AR in kidney transplant patients using a meta-analysis. Materials and Methods: To perform our meta-analysis, eligible studies about HLA-G 14-bp insertion/deletion polymorphism and AR were searched in electronic databases until 1 June 2021. Finally, a total of 336 patients with AR and 952 patients without AR in relation to kidney transplantation were analyzed from a total of nine studies. Results: In our results, the Del allele and Ins/Del+Del/Del and Del/Del genotypes significantly increased susceptibility of AR in Asian populations [odds ratio (OR) = 2.359, 95% confidence interval (CI) = 1.568-3.550, p = 3.8 × 10^-5; OR = 3.357, 95% CI = 1.769-6.370, p = 0.002; OR = 2.750, 95% CI = 1.354-5.587, p = 0.0052 in each model, respectively]. Conclusions: Evidence of the present results indicate that HLA-G 14-bp insertion/deletion polymorphism is associated with susceptibility to AR in the Asian population.

Genetic polymorphism of HLA-G gene (G*01:03, G*01:04, and G*01:05N) in Iraqi patients with inflammatory bowel disease (ulcerative colitis and Crohn’s disease)

Background

Human leukocyte antigen-G (HLA-G) has been proposed to influence susceptibility to inflammatory bowel disease (IBD). Therefore, the genetic association between HLA-G alleles and two clinical phenotypes of IBD (ulcerative colitis [UC] and Crohn’s disease [CD]) was evaluated in Iraqi patients. A case-control study was performed on 50 UC and 50 CD patients and 100 healthy controls (HC). Three HLA-G alleles (G*01:03, G*01:04, and G*01:05N) were determined using sequence-specific polymerase chain reaction assay followed by product digestion with restriction endonucleases (Hinf-I, BseR-I, and PpuM-I, respectively).

Results

The G*01:03 allele was not detected in IBD patients (UC and CD) or HC, while G*01:04 and G*01:05N alleles showed polymorphic frequencies. The allele G*01:04 was significantly associated with susceptibility to UC (odds ratio [OR] = 2.55; 95% confidence interval [CI] = 1.27–5.13; corrected probability [pc] = 0.018) and CD (OR = 4.45; 95% CI = 2.11–9.41; pc < 0.001). The allele G*01:05N was also associated with increased risk of UC (OR = 4.17; 95% CI = 1.32–13.21; pc = 0.032) and CD (OR = 4.75; 95% CI = 1.53–14.78; pc = 0.014). These associations were more pronounced in IBD (UC + CD), and a significantly increased risk for IBD was found with the alleles G*01:04 (OR = 3.32; 95% CI = 1.86–5.95; pc < 0.001) and G*01:05N (OR = 4.46; 95% CI = 1.59–12.47; pc = 0.008). A stratification of IBD patients according to some demographic and clinical characteristics revealed that frequencies of both alleles showed no significant differences between the subgroups of patients in each stratum. Soluble HLA-G was not influenced by HLA-G alleles in patients or HC. UC was an exception, and the presence of G*01:04 allele was associated with a significantly higher mean of soluble HLA-G compared to patients without the allele (189.6 ± 24.0 vs. 168.6 ± 27.2 ng/mL; p = 0.033).

Conclusion

This study indicated that HLA-G*01:04 and HLA-G*01:05N alleles may influence susceptibility to UC and CD in Iraqi patients.

HLA-G Genotype/Expression/Disease Association Studies: Success, Hurdles, and Perspectives

The non-classical HLA-G is a well-known immune-modulatory molecule. In physiological condition, HLA-G surface expression is restricted to the maternal–fetal interface and to immune-privileged adult tissues, whereas soluble forms of HLA-G are detectable in various body fluids. HLA-G can be de novo expressed in pathological conditions including tumors, chronic infections, or after allogeneic transplantation. HLA-G exerts positive effects modulating innate and adaptive immune responses and promoting tolerance, or detrimental effects inducing immune escape mechanisms. HLA-G locus, in contrast to classical HLA class I gene, is highly polymorphic in the non-coding 3′ untranslated region (UTR) and in the 5′ upstream regulatory region (5′ URR). Variability in these regions influences HLA-G expression by modifying mRNA stability or allowing posttranscriptional regulation in the case of 3′ UTR or by sensing the microenvironment and responding to specific stimuli in the case of HLA-G promoter regions (5′ URR). The influence of genetic variations on the expression of HLA-G makes it an attractive biomarker to monitor disease predisposition and progression, or response to therapy. Here, we summarize the current knowledge, efforts, and obstacles to generate a general consensus on the correlation between HLA-G genetic variability, protein expression, and disease predisposition. Moreover, we discuss perspectives for future investigation on HLA-G genotype/expression in association with disease predisposition and progression.

HLA-G14bp ins/del polymorphism and post-transplant weight gain in kidney transplantation: potential implications beyond tolerance

BACKGROUND

Human leukocyte antigen (HLA)-G is a non-classical HLA molecule with immunomodulant and immunosuppressive functions, involved in transplantation tolerance. HLA-G14bp ins/del polymorphism in exon 8 has been associated with allograft rejection and kidney transplant outcome, with controversial results. We investigated associations of HLA-G14bp ins/del polymorphism on onset of some of the main post-transplant risk factors, like excess body weight, lipid abnormalities, increased fasting plasma glucose. Polymorphisms of cytokines with both immunosuppressive and metabolic effects were also assessed for comparisons and associated analysis.

METHODS

The present study involved kidney transplant recipients (n = 173) in which body mass index, cholesterol, triglycerides, fasting plasma glucose were registered in the first years after transplantation and analyzed in association with genotypes. Presence of hypertension and smoking habits, demographic, transplant-related and therapeutic data of patients were also recorded. Polymerase chain reaction, sequence-specific primer amplification and Taqman allelic discrimination techniques were used for genotyping of HLA-G14bp ins/del, interleukin (IL)-10(-1082G > A,-819 T > C,-592A > C), transforming growth factor-β(+ 869 T > C,+915C > G), IL-6(-174G > C), tumor necrosis factor-α(-308G > A) and IL-18(-137G > C,-607C > A). Effects of genotypes on clinical markers at each time point (pre-transplant and 1 to 5 years after transplant) were analyzed using a repeated-measures general linear model analysis; adjustment for potential confounders was performed.

RESULTS

Results showed that HLA-G14bp ins/ins was significantly associated with obesity, in particular after transplantation (3 years, p = 0.002, OR = 4.48, 95% CI:1.76-11.41). Post-transplant body mass index was significantly increased in HLA-G14bp ins/ins carriers (3 and 4 years, p = 0.033 and p = 0.044); effects of HLA-G14bp genotypes on post-transplant BMI were confirmed by using repeated-measures analysis and after controlling for confounding variables. Cytokine genotypes did not associate with the examined factors.

CONCLUSIONS

The study of transplanted patients allowed to evidence a potential relationship between post-transplant weight gain and HLA-G14bp ins/del polymorphism, previously involved in rejection for its immunosuppressive/tolerogenic activity. This novel association could widen the knowledge of the role and functions of HLA-G molecules in diseases and transplantation.

Association between 14 bp insertion/deletion HLA-G functional polymorphism and insulin resistance in a cohort of Italian children with obesity

BACKGROUND

The non-classical HLA-class I molecule-g (HLA-G) gene shows a deletion/insertion (del/ins) polymorphism of a 14-base-pair sequence (14 bp) in the exon 8 at the 3' untranslated region. The presence of the 14 bp insertion allele has been associated to lower soluble HLA-G protein production, a protein with anti-inflammatory activities. So far, no studies have investigated the relationship between HLA-G 14 bp del/ins polymorphism and metabolic features of obese children and adolescents. We aimed to assess if the HLA-G ins/del polymorphism, and in particular the HLA-G ins/ins genotype determining lower sHLA-G production, is associated to insulin resistance (evaluated by homeostasis model assessment [HOMA]) in a population of obese children.

METHODS

We enrolled 574 obese children and adolescents. Anthropometric and laboratory data were collected. The white blood cell (WBC) count was evaluated as surrogate marker of inflammation. C-reactive protein (CRP) was available in 48 patients. HOMA was calculated. Patients were genotyped for the HLA-G del/ins polymorphism.

RESULTS

Subjects carrying the HLA-G ins/ins genotype, presented with higher HOMA, WBC and CRP values, compared to del/ins and del/del genotypes (P ≤ 0.0009, ≤0.02 and ≤0.0001, respectively). Comparison of the regression line slopes, performed for HOMA and WBC on the basis of HLA-G genotypes, showed that subjects carrying the HLA-G ins/ins genotype presented with a stronger correlation between HOMA and WBC, compared to the other genotypes (Model r2 3.13%, P ≤ 0.006).

CONCLUSIONS

We showed a strong association between HLA-G 14 bp ins/ins genotype and HOMA in obese children and adolescents. This association could be hypothetically modulated by subclinical inflammation.

Genetic association between HLA-G 14-bp polymorphism and diseases: A systematic review and meta-analysis

BACKGROUND

HLA-G is an immune checkpoint molecule. Since a differential molecule expression has been reported even for healthy individuals, many studies have focused on polymorphisms at HLA-G regulatory regions, particularly the 3' untranslated region (3'UTR). The presence/absence of a 14-bp sequence was the first polymorphism described and it is the most studied in association between HLA-G and disorders.

METHODS

In this study, we performed a systematic review and meta-analysis of all association studies published regarding the HLA-G 14-bp.

RESULTS

We verified association between 14-bp alleles and diseases in the following situations: (1) presence of 14-bp (insertion) conferred susceptibility to preeclampsia (child alleles evaluated) and systemic lupus erythematosus (OR = 1.42; 95%CI = 1.04-1.93; p = 0.026 and OR = 1.13; 95%CI = 1.01-1.27, p = 0.028); (2) 14-bp absence (deletion) was associated with increased risk to breast cancer (OR = 1.23; 95%CI = 1.06-1.43; p = 0.006) and human Cytomegalovirus infection (OR = 2.06; 95%CI = 1.60-2.64; p < 0.0001); and (3) a risk association was observed between the group of reproductive disorders and the 14-bp insertion (OR = 1.12; 95%CI = 1.01-1.24; p = 0.034).

CONCLUSIONS

Considering that others 14-bp associations were inconclusive and that other variation sites observed at HLA-G 3'UTR exhibit a proven role on post-transcriptional regulation of HLA-G expression, the complete 3'UTR segment should be analyzed in terms of disease susceptibility, instead of a single polymorphism.

HLA-G 14-bp polymorphism affects the age of onset in Type I Diabetes Mellitus

Type I diabetes mellitus (T1DM) is an organ-specific autoimmune disorder affecting the insulin-producing pancreatic cells. T1DM genetic association studies have so far revealed the involvement of more than 40 loci, with particularly strong associations for the human leucocyte antigens (HLA). Further to the well-established HLA class II associations, the immunomodulatory elements in the telomeric major histocompatibility complex locus, specifically nonclassical HLA class I, were also associated with T1DM, either in conferring susceptibility or by contributing to the overall pathogenesis. This study investigates the involvement of a 14-bp deletion polymorphism (rs371194629) at the 3' untranslated region of HLA-G in the context of T1DM and age of onset. The frequency of the polymorphism was determined in unrelated T1DM Cypriot patients and findings that emerge from this study show a strong association between the HLA-G 14-bp polymorphism and T1DM with respect to the age of onset. Specifically, the deletion/deletion (DEL/DEL) genotype was found to be associated with an early age of onset (P = 0.001), while the presence of the insertion allele (INS) was associated to a later age of onset (P = 0.0001), portraying a possible dominant effect over the deletion allele, a role in delaying disease onset and an overall involvement of HLA-G in the pathogenesis of type I diabetes mellitus.

HLA-G Molecules in Autoimmune Diseases and Infections

Human leukocyte antigen (HLA)-G molecule, a non-classical HLA-Ib molecule, is less polymorphic when compared to classical HLA class I molecules. Human leukocyte antigen-G (HLA-G) was first detected on cytotrophoblast cells at the feto-maternal interface but its expression is prevalent during viral infections and several autoimmune diseases. HLA-G gene is characterized by polymorphisms at the 3' un-translated region and 5' upstream regulatory region that regulate its expression and are associated with autoimmune diseases and viral infection susceptibility, creating an unbalanced and pathologic environment. This review focuses on the role of HLA-G genetic polymorphisms, mRNA, and protein expression in autoimmune conditions and viral infections.

Insights into HLA-G Genetics Provided by Worldwide Haplotype Diversity

Human leukocyte antigen G (HLA-G) belongs to the family of non-classical HLA class I genes, located within the major histocompatibility complex (MHC). HLA-G has been the target of most recent research regarding the function of class I non-classical genes. The main features that distinguish HLA-G from classical class I genes are (a) limited protein variability, (b) alternative splicing generating several membrane bound and soluble isoforms, (c) short cytoplasmic tail, (d) modulation of immune response (immune tolerance), and (e) restricted expression to certain tissues. In the present work, we describe the HLA-G gene structure and address the HLA-G variability and haplotype diversity among several populations around the world, considering each of its major segments [promoter, coding, and 3′ untranslated region (UTR)]. For this purpose, we developed a pipeline to reevaluate the 1000Genomes data and recover miscalled or missing genotypes and haplotypes. It became clear that the overall structure of the HLA-G molecule has been maintained during the evolutionary process and that most of the variation sites found in the HLA-G coding region are either coding synonymous or intronic mutations. In addition, only a few frequent and divergent extended haplotypes are found when the promoter, coding, and 3′UTRs are evaluated together. The divergence is particularly evident for the regulatory regions. The population comparisons confirmed that most of the HLA-G variability has originated before human dispersion from Africa and that the allele and haplotype frequencies have probably been shaped by strong selective pressures.

Serological testing for celiac disease in adults

BACKGROUND AND AIM

We present a systematic review on the performance of currently available methods for serological diagnosis of celiac disease (CD) and the role of human leukocyte antigen (HLA) typing.

OBJECTIVE

A literature survey was conducted using PubMed, MeSH database, Web of Science as well as manual searches.

RESULTS

Tissue transglutaminase antibodies (tTG) (IgA) (tested in nine studies) show sensitivities and specificities in the range of 0.76-0.968 and 0.909-0.98, and deamidated gliadin peptide (DGP) (IgA and IgG) (tested in eight studies) show sensitivities and specificities in the range of 0.69-0.984 and 0.903-1. Endomysial antibodies (EMA) (tested in five studies) show sensitivities and specificities in the range of 0.61-0.937 and 0.98-1, respectively. Combination assays (tested in three studies) using DGP + tTG and DGP (IgA + IgG) show sensitivities and specificities in the range of 0.87-1 and 0.8-1, respectively. HLA DQ2/DQ8 may be necessary for the development of CD-HLA DQ2 in particular. A possible close correlation may also exist between CD and HLA-G.

CONCLUSION

DGP and tTG for serological testing for CD show equivalent diagnostic performance. More studies with, in particular, DGP alone and in combination with tTG are necessary before a firm recommendation can be made. HLA typing to exclude CD may still be controversial. It still seems premature to diagnose celiac disease in adults based on serology alone.

Advances in coeliac disease

PURPOSE OF REVIEW

This article critically summarizes the recent scientific and clinical advances in coeliac disease.

RECENT FINDINGS

Epidemiological studies have shown that coeliac disease is as common in parts of Asia, Africa and Eastern Europe as in the western world. Genome-wide association studies continue to identify genetic susceptibilities that are both unique to coeliac disease and overlap with other autoimmune diseases. Human leukocyte antigen genotyping offers additional sensitivity in detecting coeliac disease in individuals who have self-prescribed gluten-free diets (GFD) or have atypical presentations. Immunological advances have highlighted the potential proinflammatory pitfalls of vitamin A supplementation in active coeliac disease and have enabled identification of oat and barley subsets that may be safely incorporated into coeliac diets. Large population-based studies have expanded our knowledge of the long-term risks of coeliac disease, in addition to excluding infertility as a cause for concern once a GFD has been established.

SUMMARY

The long-term implications of active coeliac disease emphasize the need for early detection and strict adherence to GFD, which remains the cornerstone of management. Technological advances in food modulation and immuno-therapies offer promise, but remain in the translational phases of clinical trials at present.