Patients with early onset of type 1 diabetes have significantly higher GG genotype at position 49 of the CTLA4 gene

Cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) +49A>G (rs231775) gene polymorphism is not associated with COVID-19 severity and mortality in an Iranian population

Introduction

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) regulates T cell immune responses as an immune activation inhibitor. Literature reviews suggest that COVID-19 is associated with dysregulation of the inflammatory immune response. The purpose of the present hospital-based case-control study was to evaluate the genetic association of the CTLA4 +49A > G (rs231775) Single Nucleotide Polymorphism (SNP) with COVID-19 severity and mortality among the Iranian people.

Method

Genomic DNA of peripheral blood nuclear cells was extracted from the 794 COVID-19 patients and 167 control individuals. The polymorphic site of rs231775 was genotyped using the PCR-RFLP technique. Also, to identify whether this genetic variation was related to CTLA-4 mRNA expression, total RNA was extracted from 178 COVID-19 patients and 70 controls. The mRNA levels of CTLA-4 were determined using real-time PCR.

Result

There were no statistically significant differences found in the genotype and allele frequencies among the different genetic models with regards to the severity and mortality of COVID-19. Furthermore, there was no significant association between rs231775 genotypes and CTLA-4 mRNA expression in patients.

Conclusion

Our findings demonstrated that SARS-CoV-2 infection is not associated with rs231775 in the Iranian people. More investigations are crucial to show how this genetic variation affects other ethnic groups. Given the importance of CTLA-4 in regulating immune responses, further studies are recommended to examine other CTLA-4 SNPs and the function of this gene in COVID-19 patients.

Coaggregation of Asthma and Type 1 Diabetes in Children: A Narrative Review

Asthma and type 1 diabetes mellitus (T1DM) are two of the most frequent chronic diseases in children, representing a model of the atopic and autoimmune diseases respectively. These two groups of disorders are mediated by different immunological pathways, T helper (Th)1 for diabetes and Th2 for asthma. For many years, these two groups were thought to be mutually exclusive according to the Th1/Th2 paradigm. In children, the incidence of both diseases is steadily increasing worldwide. In this narrative review, we report the evidence of the potential link between asthma and T1DM in childhood. We discuss which molecular mechanisms could be involved in the link between asthma and T1DM, such as genetic predisposition, cytokine patterns, and environmental influences. Cytokine profile of children with asthma and T1DM shows an activation of both Th1 and Th2 pathways, suggesting a complex genetic-epigenetic interaction. In conclusion, in children, the potential link between asthma and T1DM needs further investigation to improve the diagnostic and therapeutic approach to these patients. The aim of this review is to invite the pediatricians to consider the potential copresence of these two disorders in clinical practice.

Comprehensive Review of Cardiovascular Diseases, Diabetes, and Hypercholesterolemia in Lebanon

The Middle East and North Africa regions, including Lebanon, have recently witnessed rapid urbanization and modernization over the last couple of decades that has led to a dramatic transformation affecting lifestyle and diet. The World Health Organization reports that the leading cause of death in Lebanon is due to cardiovascular disease (CVD) at 47% of all-cause mortality. Over the last 30 years, especially the last 10, the population of Lebanon has changed dramatically due to the effect of wars in the region and refugees seeking asylum. With a population of around 4.5 million and a relatively high rate of consanguinity in Lebanon, a variety of novel mutations have been discovered explaining several familial causes of hypercholesterolemia, diabetes mellitus, congenital heart disease, and cardiomyopathies. Due to the Syrian civil war, 1.5 million Syrian refugees now reside in Lebanon in either low-income housing or tented settlements. A National Institutes of Health study is examining diabetes and CVD in Syrian refugees in comparison to native Lebanese. We provide the first review of CVD in Lebanon in its metabolic component including coronary artery disease and its risk factors, mainly hyperlipidemia and diabetes mellitus, and its structural component, including congenital heart disease, valvular heart disease, cardiomyopathies, and heart failure. The knowledge in this review has been compiled to guide clinicians and assist researchers in efforts to recognize risk factors for disease, improve delivery of health care, and prevent and treat CVDs in Lebanon, both for the native Lebanese and Syrian refugees.

CTLA-4: From mechanism to autoimmune therapy

CD28 and CTLA-4 are both important stimulatory receptors for the regulation of T cell activation. Because receptors share common ligands, B7.1 and B7.2, the expression and biological function of CTLA-4 is important for the negative regulation of T cell responses. Therefore, elimination of CTLA-4 can result in the breakdown of immune tolerance and the development of several diseases such as autoimmunity. Inhibitory signals of CTLA-4 suppress T cell responses and protect against autoimmune diseases in many ways. In this review, we summarize the structure, expression and signaling pathway of CTLA-4. We also highlight how CTLA-4 defends against potentially self-reactive T cells. Finally, we discuss how the CTLA-4 regulates a number of autoimmune diseases that indicate manipulation of this inhibitory molecule is a promise as a strategy for the immunotherapy of autoimmune diseases.

Analysis of CTLA-4+49A/G gene polymorphism in cases with leprosy of Azerbaijan, Northwest Iran

Leprosy, which is developed by the obligate intracellular Mycobacterium leprae (ML); has different manifestations, associated with the host immune responses. The protective immune response against ML includes T-cell-mediated immunity. The CTLA-4 has a great impact as a negative regulator of the immune response and maintenance of peripheral tolerance. This study analyzed the relationship between CTLA-4+49A/G gene polymorphism and clinical manifestation of leprosy disease and susceptibility among the Azeri population living Northwest Iran. One hundred and ninety-two leprosy patients and 185 healthy controls participated in the study. CTLA-4+49A/G genotyping was conducted via tetra-primer amplification refractory mutation system-polymerase chain reaction (T-ARMS-PCR) analysis. The allelic and genotypic frequencies of +49A/G gene polymorphism were similar in controls and patients. However, older ages, older age of onset and over-representation in male were observed in lepromatous leprosy patient carriers of GG genotype. The current study demonstrates that although CTLA-4+49A/G polymorphism was not correlated with a higher genetic risk for leprosy, the presence of a GG genotype was associated with older ages, older age of onset and over-representation in male in Iranian Azeri population.

Genetic Epidemiology of Type 1 Diabetes in the 22 Arab Countries

Type 1 diabetes (T1D) is a complex autoimmune disorder that results from the T cell-mediated destruction of the pancreatic β cells and is due to interactions between environmental and genetic factors. Although Arabs have one of the highest global incidence and prevalence rates of T1D, unfortunately, there is a dearth of information regarding the genetic epidemiology of T1D in the Arab world. Arabs share several HLA haplotypes with other ethnic groups, which confer either susceptibility or protection to T1D, but they have specific haplotypes that are distinctive from other ethnicities. Among different Arab countries, several non-HLA genes were reported to be associated with susceptibility to T1D, including CTLA4, CD28, PTPN22, TCRβ, CD3z, IL15, BANK1, and ZAP70. In Arab countries, consanguinity, endogamy, and first-cousin marriage rates are some of the highest reported worldwide and are responsible for the creation of several inbreeding communities within the Arab world that have led to an increase in homozygosity of both the HLA haplotypes and non-HLA genes associated with either protection or susceptibility to T1D among Arabs. Homozygosity reduces the HLA complexity and is expected to facilitate our understanding of the mode of inheritance of HLA haplotypes and provide valuable insight into the intricate genotype-phenotype correlations in T1D patients. In this review, based on literature studies, I will discuss the current epidemiological profile and molecular genetic risks of Arabs with T1D.

Analysis of DLA-DQB1 and polymorphisms in CTLA4 in Cocker spaniels affected with immune-mediated haemolytic anaemia

BACKGROUND

Cocker spaniels are predisposed to immune-mediated haemolytic anaemia (IMHA), suggesting that genetic factors influence disease susceptibility. Dog leukocyte antigen (DLA) class II genes encode major histocompatibility complex (MHC) molecules that are involved in antigen presentation to CD4(+) T cells. Several DLA haplotypes have been associated with autoimmune disease, including IMHA, in dogs, and breed specific differences have been identified. Cytotoxic T lymphocyte antigen 4 (CTLA4) is a critical molecule involved in the regulation of T-cell responses. Single nucleotide polymorphisms (SNPs) in the CTLA4 promoter have been shown to be associated with several autoimmune diseases in humans and more recently with diabetes mellitus and hypoadrenocorticism in dogs. The aim of the present study was to investigate whether DLA-DQB1 alleles or CTLA4 promoter variability are associated with risk of IMHA in Cocker spaniels.

RESULTS

There were a restricted number of DLA-DQB1 alleles identified, with a high prevalence of DLA-DQB1*007:01 in both groups. A high prevalence of DLA-DQB1 homozygosity was identified, although there was no significant difference between IMHA cases and controls. CTLA4 promoter haplotype diversity was limited in Cocker spaniels, with all dogs expressing at least one copy of haplotype 8. There was no significant difference comparing haplotypes in the IMHA affected group versus control group (p = 0.23). Homozygosity for haplotype 8 was common in Cocker spaniels with IMHA (27/29; 93 %) and in controls (52/63; 83 %), with no statistically significant difference in prevalence between the two groups (p = 0.22).

CONCLUSIONS

DLA-DQB1 allele and CTLA4 promoter haplotype were not found to be significantly associated with IMHA in Cocker spaniels. Homozygosity for DLA-DQB1*007:01 and the presence of CTLA4 haplotype 8 in Cocker spaniels might increase overall susceptibility to IMHA in this breed, with other genetic and environmental factors involved in disease expression and progression.

Common variants on cytotoxic T lymphocyte antigen-4 polymorphisms contributes to type 1 diabetes susceptibility: evidence based on 58 studies

In the past decade, a number of case–control studies have been carried out to investigate the relationship between the CTLA4 gene polymorphisms and type 1 diabetes (T1D). However, these studies have yielded contradictory results. To investigate this inconsistency, we performed a meta-analysis of all available studies dealing with the relationship between the CTLA4 polymorphism and T1D. In total, 58 association studies on two CTLA4 polymorphisms (G49A and C60T) and risk of T1D, including a total of 30,723 T1D cases and 45,254 controls were included. In a combined analysis, the summary per-allele odds ratio (OR) for T1D of the G49A and C60T polymorphism was 1.42 [95% confidence interval (CI): 1.31–1.53, P<10⁻⁵] and 1.23 (95% CI: 1.18–1.29, P<10⁻⁵), respectively. Significant results were also observed using dominant or recessive genetic model. In the subgroup analysis by ethnicity and sample size, significantly increased risks were also found for these polymorphisms. This meta-analysis demonstrated that the G49A and C60T polymorphism of CTLA4 is a risk factor associated with increased T1D susceptibility, but these associations vary in different ethnic populations.

Association between the CTLA-4 +49A/G polymorphism and type 1 diabetes: a meta-analysis

BACKGROUND

+49A/G polymorphism of the cytotoxic T-lymphocyte-associated antigen-4 gene (CTLA-4) has been associated with type 1 diabetes (T1D). However, results were inconsistent. The aim of this study was to quantitatively summarize the evidence for CTLA-4 +49A/G polymorphism and T1D.

METHODS

Electronic search of PubMed was conducted to select studies. Case-control studies containing available genotype frequencies of CTLA-4 +49 were chosen, and the odds ratio (OR) with 95% confidence interval (CI) was used to assess the strength of this association.

RESULTS

49 case-control studies, including 8976 cases and 11012 controls, were identified. 8 studies were eliminated from the total 49 studies because of p<0.05 (p value for Hardy-Weinberg equilibrium in the control group) in these studies, which induce significant publication bias. The overall results suggested that the variant genotypes were highly associated (p<0.01) with T1D risk in all genetic models (additive model: OR 1.345, 95% CI 1.249-1.448, p<0.001; recessive model: OR 1.530, 95% CI 1.370-1.708, p<0.001; dominant model: OR 1.409, 95% CI 1.263-1.572 p<0.001). Similarly, in subgroup analyses for ethnicity (Caucasian, Asian), the results were positive.

CONCLUSION

This meta-analysis suggests that the CTLA-4 +49A/G polymorphism is highly associated (p<0.01) with increased risk of T1D, especially in Caucasians and Asians. To validate this association, further studies with more participants worldwide are needed to examine associations between this polymorphism and T1D. Otherwise, we found that the studies of Africans are rare. More studies in Africans are needed especially.

Association of cytotoxic T-lymphocyte associated antigen 4 gene polymorphism with type 1 diabetes mellitus: a meta-analysis

To evaluate the association between costimulatory molecule cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) gene polymorphism and type 1 diabetes mellitus(T1DM), sixty-three published studies before December, 2011 were included. Meta-analysis was performed for each genotype in a random/fixed effect model. The combined odds ratio (OR) with 95% confidence interval (95%CI) was calculated to estimate the strength of the association. Overall, significant correlation was noted between CTLA-4 gene polymorphism (i.e. +49A/G, CT60A/G in a per-allele model) and the risk of T1DM (for +49A/G: OR=1.47, 95%CI=1.36-1.60, P<0.001; for CT60A/G: OR=1.31, 95%CI=1.18-1.45, P<0.001). However, no significant association was noted between C(-318)T polymorphism and T1DM. In the subgroup analysis, for +49A/G and CT60A/G, the statistically significant associations were also demonstrated in diverse racial descents (Caucasian and Asian) and age of onset (<20 years and >20 years). In conclusion, our results suggest that CTLA-4 polymorphism contributes to the susceptibility of T1DM.

Interaction between CTLA4 gene and IBD5 locus in Hungarian Crohn's disease patients

BACKGROUNDS AND AIMS

The IGR2198a_1 and IGR2096a_1 variants of the IBD5 region were found to be associated with Crohn's disease (CD) in the Hungarian population, while IGR2230a_1 does not seem to confer risk for the disease. In the present study, our aim was to investigate the statistical interaction of these three IBD5 polymorphisms with the +49 A/G substitution within the cytotoxic T lymphocyte antigen-4 (CTLA4) gene, detected previously as neutral gene variant in Hungarian IBD patients.

METHODS

A total of 305 unrelated subjects with CD and 310 healthy controls were genotyped with PCR-RFLP methods.

RESULTS

In contrast with single gene effects, after genotype stratification, the IGR2198a_1 C and IGR2096a_1 T variants were found to confer susceptibility only in subjects with CTLA4 +49 AA genotype (P = 0.008; OR = 1.86 and P = 0.016; OR = 1.74, respectively), for IGR2230a_1 no such effect on disease risk could be demonstrated.

CONCLUSION

Analysis of specific genotype combinations unfolded a possible association between the CTLA4 +49 A/G substitution and two of the observed IBD5 variants with respect to disease risk.

Association of CTLA-4 (+49A/G) gene polymorphism with type 1 diabetes mellitus in Egyptian children

OBJECTIVE

To investigate the distribution of cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) (+49 A/G) gene variants and the association of these variants with the clinical and laboratory findings in Egyptian children with Type-1 Diabetes (T1D).

METHODS

A case control study was done for 104 Egyptian children with T1D and 78 age and sex matched healthy control. CTLA-4 (+49 A/G) gene polymorphism typing was done by PCR amplification followed by restriction fragment length polymorphism (RFLP) method.

RESULTS

CTLA-4 G allele and GG homozygous genotype were significantly increased in T1D patients than in control group (P = 0.047, P = 0.048 respectively). There is no statistical difference between patient with optimal diabetic control (HbA1c < 8.5) and poor control (HbA1c ≥ 8.5) as regarding the CTLA-4 gene variant. The CTLA-4 GG genotype was statistically associated with younger age of patients (P = 0.027) and younger age of presentation (P = 0.036). Insignificant association was found between CTLA-4 alleles / genotypes and diabetic complications.

CONCLUSION

The CTLA-4 +49 GG homozygous genotype is associated with T1D in Egyptian children especially with younger age of onset and in younger patients, and not associated with grades of diabetic control or diabetic complication.

High titre of antiglutamic acid decarboxylase autoantibody is a strong predictor of the development of thyroid autoimmunity in patients with type 1 diabetes and latent autoimmune diabetes in adults

OBJECTIVE

Type 1 diabetes mellitus (T1DM) is frequently associated with autoimmune thyroid diseases (AITD), but little is known about the risk of AITD in latent autoimmune diabetes in adults (LADA). We evaluated the genetic and immunological factors involved in the development of thyroid autoimmunity in patients with LADA and T1DM.

PATIENTS AND MEASUREMENTS

One hundred and ninety T1DM and 135 LADA patients were recruited in the study. Thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TGAb), glutamic acid decarboxylase antibody (GADA) and thyroid function were measured. The cytotoxic-lymphocyte-associated antigen-4 (CTLA-4) +49A/G and CT60 polymorphisms and the human leucocyte antigen (HLA)-DQA1-DQB1 genotype were determined.

RESULTS

The prevalence of thyroid antibodies (TGAb and/or TPOAb) and thyroid dysfunction was 27·4% and 9·5% in patients with T1DM, and 21·5% and 11·1% in patients with LADA. Thyroid-antibody-positive T1DM patients had higher frequencies of GADA and HLA-DQA1*03-DQB1*0401 haplotypes than thyroid-antibody negatives (P < 0·05). Thyroid-antibody-positive LADA patients had higher GADA titre, lower C-peptide levels and higher frequencies of HLA-DQA1*03-DQB1*0401 haplotypes (P < 0·05). The CTLA-4 +49A/G and CT60 polymorphism was associated with T1DM complicated with thyroid autoimmunity (OR = 2·33 and 2·54). Logistic regression revealed that only high-titre GADA was associated with development of thyroid autoimmunity in patients with T1DM and LADA (OR = 3·50 and 3·10, respectively), and the presence of thyroid antibody predicted high risk for thyroid dysfunction in patients with T1DM and LADA (OR = 9·25 and 10·70, respectively).

CONCLUSION

Regular screening of thyroid antibody and function are recommended, especially in patients with T1DM and LADA with high GADA titre.

Prevalence of asthmatic symptoms in Lebanese patients with type 1 diabetes and their unaffected siblings compared to age-matched controls

Patients with type 1 diabetes (a TH1 disease) have been reported to be at a lower risk of developing asthma (a TH2 disease). Both diseases are affected by environmental and genetic factors. Our objective is to examine this relationship in Lebanon, a Middle-Eastern country, where no previous similar studies are available. This is a cross-sectional observational study conducted at the Chronic Care Center, a referral medical center for type 1 diabetics. Patients with type 1 diabetes aged 6-39 years old, their unaffected siblings and age-matched control completed the International Primary Care Airways Group asthma screening questionnaire. The prevalence of asthma symptoms was compared among the three groups and separately within a subgroup of diabetics in relation to their carrier state of previously collected genetic data. Among 305 diabetics, 776 siblings and 187 controls, diabetics were at lower risk of having any asthma symptoms than controls; OR 0.48 (95% CI 0.32-0.72, p < 0.001) and siblings were at lower risk than diabetics and controls; OR 0.64 (95% CI 0.45-0.91, p = 0.01) and 0.28 (95% CI 0.19-0.42, p < 0.001), respectively. Among 66 diabetics, carriers of the HLA-DQB1*0201 allele were at lower risk of having any asthma symptoms than non-carriers (25.5 vs. 53.3%, p = 0.04). Only a statistically non-significant trend of higher risk was observed in carriers of HLA-DQB1*0301 and G allele at the 49 (A/G) nucleotide of CTLA-4 gene. The TH1-TH2 paradigm might partially explain these findings, since siblings were the least to report asthma symptoms. Future research is needed with diagnostic tests for asthma and extensive genetic testing.

Association of single nucleotide polymorphisms in cytotoxic T-lymphocyte antigen 4 and susceptibility to autoimmune type 1 diabetes in Tunisians

In addition to HLA and insulin genes, the costimulatory molecule CTLA-4 gene is a confirmed type 1 diabetes (T1D) susceptibility gene. Previous studies investigated the association of CTLA-4 genetic variants with the risk of T1D, but with inconclusive findings. Here, we tested the contributions of common CTLA-4 gene variants to T1D susceptibility in Tunisian patients and control subjects. The study subjects comprised 228 T1D patients (47.8% females) and 193 unrelated healthy controls (45.6% females). Genotyping for CTLA-4 CT60A/G (rs3087243), +49A/G (rs231775), and -318C/T (rs5742909) was performed by PCR-restriction fragment length polymorphism (RFLP) analysis. The minor-allele frequencies (MAF) for the three CTLA-4 variants were significantly higher in T1D patients, and significantly higher frequencies of homozygous +49G/G and homozygous CT60G/G genotypes were seen in patients, which was confirmed by univariate regression analysis (taking the homozygous wild type as a reference). Of the eight possible three-locus CTLA-4 haplotypes (+49A/G, -318C/T, and CT60A/G) identified, multivariate regression analysis confirmed the positive association of ACG (odds ratio [OR], 1.93; 95% confidence interval [CI], 1.26 to 2.94), GCG (OR, 2.40; 95% CI, 1.11 to 5.21), and GTA (OR, 4.67; 95% CI, 1.52 to 14.39) haplotypes with T1D, after confounding variables were adjusted for. Our results indicate that CTLA-4 gene variants are associated with increased T1D susceptibility in Tunisian patients, further supporting a central role for altered T-cell costimulation in T1D pathogenesis.

Gatekeepers of intestinal inflammation

The intestine is subjected to a barrage of insults from food, bacterial flora, and pathogens. Despite this constant antigenic challenge, the mucosal tissues lining the intestinal tract remain largely under control. The mechanisms regulating the homeostatic balance in the gut have been investigated for many years by many groups, but the precise nature of the regulatory control remains elusive. In this review, we provide an overview of pathways proposed to be involved in dampening the inflammatory response and maintaining the homeostatic balance in the intestine, and how these pathways may be disrupted in ulcerative colitis and Crohn's disease.

Type 1 diabetes susceptibility determined by HLA alleles and CTLA-4 and insulin genes polymorphisms in Brazilians

INTRODUCTION

Type 1A diabetes mellitus (T1ADM) is a multifactorial disease in which genetic and environmental aspects are important to its development. The association of genetic variations with disease has been demonstrated in several studies; however, the role of some gene loci has not yet been fully elucidated.

OBJECTIVE

To compare the frequency of HLA alleles and polymorphism in CTLA-4 and insulin genes in Brazilians with T1ADM and individuals without the disease, as well as to identify genetic markers that are able to discriminate between diabetic and non-diabetic individuals.

METHODS

The presence of HLA DQB1, DQA1 and DRB1 alleles, as well as the -2221 MspI polymorphism in the insulin gene and 49 A/G in the CTLA-4 gene were identified by the 'Time-resolved fluorometer' technique after hybridization with probes labeled with Eu (III) / Sm (III) and Tb (III).

RESULTS

The DQB1 *0302 and DQA1 *03 alleles were identified as predisposed to T1ADM, and the DQB1 *0301 allele presented a protective effect against the disease.The DQA1 label proved to be able to differentiate between 71.13% of the diabetic and non-diabetic individuals.This value increased to 82.47% when the DQB1 label was added. No significant difference in the frequency of polymorphisms in the insulin and CTLA-4 genes was observed between the two groups.

CONCLUSIONS

The genetic markers that best characterized and discriminated diabetic and non-diabetic individuals were the HLA DQA1 and DQB1.alleles.

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.

+49G > A polymorphism in the cytotoxic T-lymphocyte antigen-4 gene increases susceptibility to hepatitis B-related hepatocellular carcinoma in a male Chinese population

Cytotoxic T-lymphocyte antigen 4 (CTLA-4) is an important regulator and functions negatively in immune response. Its nonsynonymous polymorphism +49G > A (dbSNP: rs231775) has been linked to an elevated risk of T-cell-mediated autoimmune diseases, infectious diseases, and even carcinomas. Here, we examined the genotypes at rs231775 of 1003 subjects in a Han Chinese population to detect the association between this single-nucleotide polymorphism (SNP) and hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) susceptibility, including 375 HBV-related HCC patients, 209 non-HCC patients with HBV infection, and 419 healthy controls. Our results indicated a weak trend for the relationship between rs231775 and HBV-related HCC susceptibility, although the statistical level was not significant. However, a significant difference was identified in males between HBV-related HCC patients and healthy controls. The data revealed that the frequency of the A/A genotype was higher in patients compared with healthy controls (odds ratio [OR] = 1.79, 95% confidence interval [95% CI] 1.05-3.08). The G allele appeared to have a protective effect in developing HBV-related HCC. Subjects with the A allele had higher HCC susceptibility than those with the G allele (OR = 1.31, 95% CI 1.03-1.66). These results suggested that the A/A genotype and A allele of rs231775 increased the risk of developing HBV-related HCC in a male Chinese population.

The role of NF-kappaB and Smad3 in TGF-beta-mediated Foxp3 expression

The transcription factor Foxp3 is essential for the development of functional, natural Treg (nTreg), which plays a prominent role in self-tolerance. Suppressive Foxp3(+) Treg cells can be generated from naïve T cells ex vivo, following TCR and TGF-beta1 stimulations. However, the molecular contributions from the different arms of these pathways leading to Foxp3 expression are not fully understood. TGF-beta1-activated Smad3 plays a major role in the expression of Foxp3, since TGF-beta1-induced-Treg generation from Smad3(-/-) mice is markedly reduced and abolished by inactivating Smad2. In the TCR pathway, deletion of Bcl10, which activates NF-kappaB, markedly reduces both IL-2 and Foxp3 production. However, partial rescue of Foxp3 expression occurs on addition of exogenous IL-2. TGF-beta1 significantly attenuates NF-kappaB binding to the Foxp3 promoter, while inducing Foxp3 expression. Furthermore, deletion of p50, a NF-kappaB subunit, results in increased Foxp3 expression despite a decline in the IL-2 production. We posit several TCR-NF-kappaB pathways, some increasing (Bcl10-IL-2-Foxp3) while others decreasing (p50-Foxp3) Foxp3 expression, with the former predominating. A better understanding of Foxp3 regulation could be useful in dissecting the cause of Treg dysfunction in several autoimmune diseases and for generating more potent TGF-beta1-induced-Treg cells for therapeutic purposes.

Associations of the CTLA-4 polymorphisms with type 1 diabetes in a Chilean population: case-parent design

CTLA-4 plays a key role in T cells regulation. We analysed the CTLA-4 +49A/G and -318C/T polymorphisms in 178 cases of type 1 diabetes and their parents (534 individuals) from Santiago, Chile. A significant overall association with T1D (p=0.028) was observed, possibly due to an overtransmission of the G-T haplotype.

Cytotoxic T lymphocyte-Associated Antigen +49G Variant Confers Risk for Anti-CCP- and Rheumatoid Factor-Positive Type of Rheumatoid Arthritis Only in Combination with CT60G Allele

Controversial observations have been published on the association of the cytotoxic T lymphocyte associated antigen gene's variants with rheumatoid arthritis (RA). After genotyping 428 patients and 230 matched controls, the prevalence of the CT60^∗G allele was more frequent in RF- and/or anti-CCP-seropositive RApatients, compared to the healthy controls (P < .001). Regression analysis revealed that the CT60^∗G allele is a possible predisposing factor for RA in these subgroups. No accumulation of the +49^∗G allele was found among patients, and this variant was not found to correlate with RA. Assaying the possible genotype variations, the +49^∗G-CT60^∗G allelic combination was accumulated in seropositive RA-subtypes, and was associated with the risk of RA (OR = 1.73, P = .001 for the whole RA-population). Although the +49^∗G allele did not mean a predisposition to RA alone, in combination with CT60^∗G it, also conferred risk, suggesting that the +49A/G variant is associated with the risk of RA only in certain haplotypes.

Association between genotypes and phenotypes in coeliac disease

BACKGROUND

Coeliac disease (CD) is a genetically driven immunological intolerance to dietary gluten with a wide range of clinical presentations. The aim of this study was to investigate the heritability of the phenotype in CD and the influence on the phenotype of different genes associated with the disease.

PATIENTS AND METHODS

One hundred and seven families with at least 2 siblings with CD were collected. The patients were grouped in symptom grades on the basis of the clinical presentation, the age at diagnosis, and sex. Stratification analyses of the human leucocyte antigen-DQA1 and human leucocyte antigen-DQB1 genotypes, the CTLA4 +49A/G polymorphism, the CTLA4 haplotype MH30*G:-1147*T:+49*A:CT60*G:CT61*A, and the 5q31-33 loci were done.

RESULTS

The heritability of the phenotype was estimated to be 0.45. Significant association and linkage was found between the clinical presentation and the CTLA4 +49A/G polymorphism but not for the other genotypes. No correlation was found between genotypes and age at diagnosis or sex.

CONCLUSIONS

Our results indicate that the heritability is determiner of the phenotype in CD. The CTLA4 +49A/G polymorphism is correlated to the clinical presentation: the AA genotype is associated with clinically silent disease.

A common CTLA4 polymorphism confers susceptibility to autoimmune thyroid disease in celiac children

BACKGROUND

Cytotoxic T-lymphocyte-associated protein 4 (CTLA4) is a strong candidate gene in autoimmunity susceptibility. In particular, the CTLA4 CT60 A/G dimorphism has been associated with celiac disease (CD) and was reported to be strongly associated with autoimmune thyroid disease (AITD).

AIMS

This study aimed to investigate the possible influences of the CTLA4 CT60 A/G polymorphism in the susceptibility of Italian children to CD and in the predisposition to develop AITD in children with CD.

PATIENTS AND METHODS

We genotyped 317 Italian celiac children, including 44 patients (13.9%) who developed AITD after CD diagnosis and 350 controls.

RESULTS

The CTLA4 CT60 GG genotype distribution did not show any significant difference between children with CD and control population (p=0.4). On the contrary, the frequency of the GG genotype was significantly higher in patients with CD complicated with AITD than in control subjects (p=0.002) and CD patients without AITD (p=0.02).

CONCLUSION

Our data show a significant effect of the CTLA4 CT60G allele at the homozygous state on the risk of developing AITD in children with CD and suggest that the reported association of the CTLA4 CT60 A/G polymorphism with CD is limited to the subgroup of patients who are or will be complicated with AITD.

[Susceptibility genetic variants in Hungarian morbus Crohn and ulcerative colitis patients]

We examined several susceptibility genetic variants to inflammatory bowel disease (Crohn's disease, ulcerative colitis) in Hungarian population, such as the CARD15 R702W, G908R, 1007finsC genetic variants, the SLC22A4 C1672T and SLC22A5 G-207C variants and their determined TC haplotype, the CTLA4 gene A+49G genetic variant and the rs10889677 C/A, rs2201841 T/C, rs1884444 G/T variants of the IL23R gene. We examined 201 adult patients with Crohn's disease, 241 adult patients with ulcerative colitis and 19 pediatric patients with Crohn's disease. For control 235 adult and 49 pediatric subjects were used. The genotyping was carried out using PCR/RFLP methods and direct sequencing. From the CARD15 gene mutations in the adult Crohn's disease population the 1007finsC, while in the pediatric population the 1007finsC and the G908R were significantly associated with an increased risk for Crohn's disease. We found no significant differences comparing the results of the patients and the controls by the SLC22A4, SLC22A5 genetic variants and the TC haplotype. The A+49G variant of the CTLA4 gene was not an independent determinant to inflammatory bowel disease. We found that the IL23R gene variants, rs10889677 C/A and rs2201841 T/C appear to increase susceptibility to Crohn's disease. It depends on the different populations whether this genetic variant means an obligatory risk factor to inflammatory bowel disease.

T cell cytokine gene polymorphisms in canine diabetes mellitus

Insulin-deficiency diabetes in dogs shares some similarities with human latent autoimmune diabetes of adults (LADA). Canine diabetes is likely to have a complex pathogenesis with multiple genes contributing to overall susceptibility and/or disease progression. An association has previously been shown between canine diabetes and MHC class II genes, although other genes are also likely to contribute to the genetic risk. Potential diabetes susceptibility genes include immuno-regulatory TH1/TH2 cytokines such as IFNgamma, IL-12, IL-4 and IL-10. We screened these candidate genes for single nucleotide polymorphisms (SNPs) in a range of different dog breeds using dHPLC analysis and DNA sequencing. Thirty-eight of the SNPs were genotyped in crossbreed dogs and seven other breed groups (Labrador Retriever, West Highland White Terrier, Collie, Schnauzer, Cairn Terrier, Samoyed and Cavalier King Charles Spaniel), which demonstrated substantial intra-breed differences in allele frequencies. When SNPs were examined for an association with diabetes by case:control analysis significant associations were observed for IL-4 in three breeds, the Collie, Cairn Terrier and Schnauzer and for IL-10 in the Cavalier King Charles Spaniel. These results suggest that canine cytokine genes regulating the TH1/TH2 immune balance might play a contributory role in determining susceptibility to diabetes in some breeds.

Infectious diseases and Type 1 diabetes in children

Type 1 diabetes (T1D) is an autoimmune disease triggered by environmental factors. Among those of infectious origin, viruses mostly associated to T1D are rubella virus, enteroviruses (Rotavirus, Coxackie B), Cytomegalovirus and mumps virus. The role of bacterial infections is still controversial, acting either as modulators or precipitating factors of an already started autoimmune process. Polymorphic genes of innate immunity, such as Toll-like receptors, nucleotide-binding oligomerization domain (NOD) 1 and NOD2 and mannose-binding lectin (MBL) genes, did not show a strict association with T1D onset, while protein tyrosine phosphatase (PTPN22), cytotoxic T-lymphocyte antigen (CTLA)4 and natural killer cells immunoglobulin-like receptor (KIR) genes appear to play an important role. However, the adaptive immune response genes (HLA) still provide the major contribution to T1D susceptibility. Here, we review the mechanism by which microorganisms might induce autoimmunity.

Functional genetic variations in cytotoxic T-lymphocyte antigen 4 and susceptibility to multiple types of cancer

Antitumor T lymphocytes play a pivotal role in immunosurveillance of malignancy. The CTL antigen 4 (CTLA-4) is a vital negative regulator of T-cell activation and proliferation. This study examined whether genetic polymorphisms in CTLA-4 are associated with cancer susceptibility. A two-stage investigation using haplotype-tagging single nucleotide polymorphism approach and multiple independent case-control analyses was performed to assess the association between CTLA-4 genotypes and cancer risk. Functional relevance of the polymorphisms was examined by biochemical assays. We found that the 49G>A polymorphism in the CTLA-4 leading sequence causing (17)Ala to (17)Thr amino acid substitution is associated with increased susceptibility to multiple cancers, including lung, breast, esophagus, and gastric cardia cancers. Genotyping in 5,832 individuals with cancer and 5,831 control subjects in northern and southern Chinese populations showed that the CTLA-4 49AA genotype had an odds ratio of 1.72 (95% confidence interval, 1.50-2.10; P = 3.4 x 10(-7)) for developing cancer compared with the 49GG genotype. Biochemical analyses showed that CTLA-4-(17)Thr had higher capability to bind B7.1 and stronger inhibitory effect on T-cell activation compared with CTLA-4-(17)Ala. T cells carrying the 49AA genotype had significantly lower activation and proliferation rates compared with T cells carrying the 49GG genotype upon stimulation. These results are consistent with our hypothesis and indicate that genetic polymorphisms influencing T-cell activation modify cancer susceptibility.

Genetic variants in T helper cell type 1, 2 and 3 pathways and gastric cancer risk in a Polish population

Host immune responses are known determinants of gastric cancer susceptibility. We previously reported an increased gastric cancer risk associated with common variants of several T helper type 1 (Th1) cytokine genes in a population-based case-control study in Warsaw, Poland. In the present study, we augmented our investigation to include additional Th1 genes as well as key genes in the Th2 and Th3 pathways. Analysis of 378 cases and 435 age- and sex-matched controls revealed associations for polymorphisms in the Th1 IL7R gene and one polymorphism in the Th2 IL5 gene. The odd ratios (ORs) for IL7R rs1494555 were 1.4 [95% confidence interval (CI), 1.0-1.9] for A/G and 1.5 (95% CI, 1.0-2.4) for G/G carriers relative to A/A carriers (P = 0.04). The ORs for IL5 rs2069812 were 0.9 (95% CI, 0.7-1.3) for C/T and 0.6 (95% CI, 0.3-1.0) T/T carriers compared with C/C carriers (P = 0.03). These results suggest that IL5 rs2069812 and IL7R rs1389832, rs1494556 and rs1494555 polymorphisms may contribute to gastric cancer etiology.

Targeting cytotoxic T-lymphocyte antigen-4 (CTLA-4): a novel strategy for the treatment of melanoma and other malignancies

Cancer immunotherapy centers on modulating the host's tumor-directed immune response. One promising approach involves augmentation of cell-mediated immunity by interrupting T-cell pathways responsible for immune down-regulation or tolerance. The discovery of cytotoxic T-lymphocyte antigen-4 (CTLA-4) and its role as a key negative regulator for T cells has prompted efforts to target this signaling molecule to improve cancer therapy. Activation, or 'priming', of naive T cells in response to tumor-cell invasion comprises a dual-signaling mechanism. Signal 1 requires tumor-associated antigen recognition by the T-cell receptor, while signal 2 occurs through binding of CD80 or CD86 (B7.1 of 2) on the antigen presenting cell (APC) with CD28 on the T cell. Importantly, there is a final step responsible for naturally occurring immune regulation; this occurs in response to competitive binding of CD80/CD86 on the APC by CTLA-4 on the T cell. This 'immune checkpoint' interrupts signal 2 and inhibits the activated T cell. Targeting CTLA-4 as an anticancer strategy: Following proof-of-concept studies in animals, fully human anti-CTLA-4 antibodies were developed and 2 are undergoing clinical evaluation. Ipilimumab and tremelimumab have shown promising antitumor activity, initially in patients with advanced melanoma. Class-specific immune-related adverse events (irAEs) were common and mostly transient and/or manageable. These events are thought to be mechanism-of-action-related, indicating immune tolerance is broken; this relation may also explain the association between irAEs and response seen in several trials. Interruption of immune inhibitory pathways via CTLA-4 blockade appears to be a promising strategy for cancer immunotherapy.

Analysis of Candidate Susceptibility Genes in Canine Diabetes

Canine diabetes is a complex genetic disease of unknown aetiology. It affects 0.005-1.5% of the canine population and shows a clear breed predisposition with the Samoyed being at high risk and the Boxer being at low risk of developing the disease. Canine diabetes is considered to be a disease homologue for human type 1 diabetes (T1D). It results in insulin deficiency as a consequence of autoimmune destruction of islet beta-cells in the pancreas and is believed to be mediated by Th1 cytokines (IFNgamma, TNFalpha, and IL-2). A number of genes have been associated with type 1 diabetes in humans, including the human leukocyte antigen region, the insulin variable number tandem repeat, PTPN22, CTLA4, IL-4, and IL-13. As yet, these genes have not been evaluated in canine diabetes. In this study, 483 cases of canine diabetes and 869 controls of known breed were analyzed for association with IFNgamma, IGF2, IL-10, IL-12beta, IL-6, insulin, PTPN22, RANTES, IL-4, IL-1alpha and TNFalpha. Minor allele frequencies were determined for these genes in each breed. These data were used for comparative analyses in a case-control study, and clear associations with diabetes were identified in some breeds with certain alleles of candidate genes. Some associations were with increased susceptibility to the disease (IFNgamma, IL-10, IL-12beta, IL-6, insulin, PTPN22, IL-4, and TNFalpha), whereas others were protective (IL-4, PTPN22, IL-6, insulin, IGF2, TNFalpha). This study demonstrates that a number of the candidate genes previously associated with human T1D also appear to be associated with canine diabetes and identifies an IL-10 haplotype which is associated with diabetes in the Cavalier King Charles Spaniel. This suggests that canine diabetes is an excellent comparative and spontaneously occurring disease model of human T1D.

No association of the cytotoxic T-lymphocyte associated gene CTLA4 +49A/G polymorphisms with Crohn’s disease and ulcerative colitis in Hungarian population samples

AIM: The goal of the current work was to analyse the prevalence of the +49A/G variant of the cytotoxic T-lymphocyte antigen 4 gene (CTLA4) in Hungarian patients with Crohn’s disease (CD) and ulcerative colitis (UC).

METHODS: A total of 130 unrelated subjects with CD and 150 with UC, and 170 matched controls were genotyped for the single nucleotide polymorphism (SNP). The genotypes were determined by using PCR/RFLP test.

RESULTS: The G allele frequency and the prevalence of the GG genotype were 38.1% and 12.3% in the CD group, 40.6% and 18.6% in the UC patients, and 37.4% and 15.9% in the control group, respectively.

CONCLUSION: The results of the current study show that carriage of the +49G SNP in heterozygous or in homozygous form does not confer risk either for CD or for UC in the Hungarian population.

Genes mediating environment interactions in type 1 diabetes

The relative risk of type 1 (autoimmune) diabetes mellitus for a sibling of an affected patient is fifteen times that of the general population, indicating a strong genetic contribution to the disease. Yet, the incidence of diabetes in most Western communities has doubled every fifteen years since the Second World War - a rate of increase that can only possibly be explained by a major etiological effect of environment. Here, the authors provide a selective review of risk factors identified to date. Recent reports of linkage of type 1 diabetes to genes encoding pathogen pattern recognition molecules, such as toll-like receptors, are discussed, providing a testable hypothesis regarding a mechanism by which genetic and environmental influences on disease progress are integrated.

Signatures of human regulatory T cells: an encounter with old friends and new players

BACKGROUND

Naturally occurring CD4+ CD25+ regulatory T cells (TReg) are involved in the control of autoimmune diseases, transplantation tolerance, and anti-tumor immunity. Thus far, genomic studies on TReg cells were restricted to murine systems, and requirements for their development, maintenance, and mode of action in humans are poorly defined.

RESULTS

To improve characterization of human TReg cells, we compiled a unique microarray consisting of 350 TReg cell associated genes (Human TReg Chip) based on whole genome transcription data from human and mouse TReg cells. TReg cell specific gene signatures were created from 11 individual healthy donors. Statistical analysis identified 62 genes differentially expressed in TReg cells, emphasizing some cross-species differences between mice and humans. Among them, several 'old friends' (including FOXP3, CTLA4, and CCR7) that are known to be involved in TReg cell function were recovered. Strikingly, the vast majority of genes identified had not previously been associated with human TReg cells (including LGALS3, TIAF1, and TRAF1). Most of these 'new players' however, have been described in the pathogenesis of autoimmunity. Real-time RT-PCR of selected genes validated our microarray results. Pathway analysis was applied to extract signaling modules underlying human TReg cell function.

CONCLUSION

The comprehensive set of genes reported here provides a defined starting point to unravel the unique characteristics of human TReg cells. The Human TReg Chip constructed and validated here is available to the scientific community and is a useful tool with which to study the molecular mechanisms that orchestrate TReg cells under physiologic and diseased conditions.

Genetics of susceptibility and severity in systemic lupus erythematosus

PURPOSE OF REVIEW

The genetic basis of systemic lupus erythematosus, a complex genetic trait, may provide important insights into autoimmune disease. Innovation in both practical and theoretical approaches will assist in accelerating the pace of discovery and our understanding of pathogenesis.

RECENT FINDINGS

Significant progress has been made in the last year with respect to the refinement of genetic intervals to promising candidate genes involved in systemic lupus erythematosus pathogenesis and specific phenotype susceptibility. This review highlights these discoveries and suggests platforms that may affect the future of analysis of this complex disease.

SUMMARY

Understanding the genetic basis for systemic lupus erythematosus disease and sub-phenotype susceptibility will have a substantial effect on the therapeutic interventions used to care for patients.

CTLA-4 gene polymorphisms and susceptibility to type 1 diabetes mellitus: a HuGE Review and meta-analysis

The authors performed a meta-analysis of 33 studies examining the association of type 1 diabetes mellitus with polymorphisms in the cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) gene, including the A49G (29 comparisons), C(-318)T (three comparisons), and (AT)n microsatellite (six comparisons) polymorphisms. The studies included 5,637 cases of type 1 diabetes and 6,759 controls (4,775 and 5,829, respectively, for analysis of the A49G polymorphism). The random-effects odds ratio for the *G (Ala) allele versus the *A (Thr) allele was 1.45 (95% confidence interval (CI): 1.28, 1.65), with significant between-study heterogeneity (p < 0.001). The effect size tended to be higher in type 1 diabetes cases with age of onset <20 years (odds ratio (OR) = 1.61), and there was a significant association between the presence of glutamic acid decarboxylase-65 autoantibodies and the *G allele among type 1 diabetes cases (OR = 1.49). Larger studies showed more conservative results (p = 0.011). After exclusion of studies with fewer than 150 subjects and studies with significant deviation from Hardy-Weinberg equilibrium in the controls, the summary odds ratio was 1.40 (95% CI: 1.28, 1.54). Available data showed no strong association for the 106-base-pair allele of the microsatellite polymorphism (OR = 0.99, 95% CI: 0.64, 1.55) or the *T allele of the C(-318)T polymorphism (OR = 0.92, 95% CI: 0.45, 1.89). This meta-analysis demonstrates that the CTLA-4*G genotype is associated with type 1 diabetes.