Association of polymorphisms in non-classic MHC genes with susceptibility to autoimmune hepatitis

Examining pathogenic concepts of autoimmune hepatitis for cues to future investigations and interventions

BACKGROUND

Multiple pathogenic mechanisms have been implicated in autoimmune hepatitis, but they have not fully explained susceptibility, triggering events, and maintenance or escalation of the disease. Furthermore, they have not identified a critical defect that can be targeted. The goals of this review are to examine the diverse pathogenic mechanisms that have been considered in autoimmune hepatitis, indicate investigational opportunities to validate their contribution, and suggest interventions that might evolve to modify their impact. English abstracts were identified in PubMed by multiple search terms. Full length articles were selected for review, and secondary and tertiary bibliographies were developed. Genetic and epigenetic factors can affect susceptibility by influencing the expression of immune regulatory genes. Thymic dysfunction, possibly related to deficient production of programmed cell death protein-1, can allow autoreactive T cells to escape deletion, and alterations in the intestinal microbiome may help overcome immune tolerance and affect gender bias. Environmental factors may trigger the disease or induce epigenetic changes in gene function. Molecular mimicry, epitope spread, bystander activation, neo-antigen production, lymphocytic polyspecificity, and disturbances in immune inhibitory mechanisms may maintain or escalate the disease. Interventions that modify epigenetic effects on gene expression, alter intestinal dysbiosis, eliminate deleterious environmental factors, and target critical pathogenic mechanisms are therapeutic possibilities that might reduce risk, individualize management, and improve outcome. In conclusion, diverse pathogenic mechanisms have been implicated in autoimmune hepatitis, and they may identify a critical factor or sequence that can be validated and used to direct future management and preventive strategies.

HLA-DRB1 GENE POLYMORPHISMS IN PEDIATRIC PATIENTS WITH TYPE 1 AUTOIMMUNE HEPATITIS AND TYPE 1 AUTOIMMUNE HEPATITIS OVERLAP SYNDROME WITH AUTOIMMUNE CHOLANGITIS

ABSTRACT BACKGROUND: Autoimmune hepatitis (AIH) is a rare chronic inflammatory liver disease associated with a loss of immunological tolerance to self-antigens. Susceptibility to AIH is partially determined by the presence of genes related to human leukocyte antigen (HLA), mainly allelic variants of DRB1. OBJECTIVE: The purpose of this study was to investigate the frequencies of the polymorphisms in HLA-DRB1 gene in children and adolescents with type 1 AIH and type 1 AIH overlap syndrome with autoimmune cholangitis (overlap syndrome, OS) in comparison to healthy sex and age-matched individuals (control group). METHODS: This is a cross-sectional study of 25 pediatric patients diagnosed with type 1 AIH and 18 with OS. Fifty-seven healthy individuals were included as controls. The polymorphisms of the HLA-DRB1 gene were evaluated by PCR and included HLA-DRB1*03, HLA-DRB1*04, HLA-DRB1*07, and HLA-DRB1*13. RESULTS: Our results showed that the presence of the allele HLA-DRB1*13 increased the chance of autoimmune cholangitis (OR=3.96, CI 1.07 to 14.61, P=0.04). The HLA-DRB1*04 and HLA- DRB1*07 have no association with the AIH and autoimmune cholangitis in a young sample. CONCLUSION: This work demonstrates an association of the main polymorphisms in the HLA-DRB1 gene to AIH with or without cholangitis in a Brazilian sample.

Association of CARD10 rs6000782 and TNF rs1799724 variants with paediatric-onset autoimmune hepatitis

Although the pathogenesis of paediatric-onset autoimmune hepatitis (pAIH) remains incompletely understood, genetic variants and environmental factors are known to be involved. Caspase recruitment domain family member 10 (CARD10) is a scaffold protein that participates in a complex pathway activating nuclear factor kappa-B (NFκB) and tumour necrosis factor alpha (TNF-α). This study aimed to investigate the association of CARD10 rs6000782 (g.37928186A > C) and TNF gene promoter rs1799724 (c.-1037C > T) variants with pAIH susceptibility in a cohort of Egyptian children. The research was also extended to assess the relationship of these variants with levels of NFκB-p65 and TNF-α. Fifty-six pAIH patients and 44 age- and sex-matched healthy controls were included. Variant genotyping was performed by polymerase chain reaction (PCR). Serum NFκB-p65 and TNF-α levels were measured using enzyme-linked immunosorbent assays (ELISAs). rs6000782 C and rs1799724 T alleles, separate or in combination, were significantly increased in pAIH patients compared to controls. Serum levels of NFκB-p65 and TNF-α were higher in pAIH differentiating both groups. Moreover, the recessive model of rs6000782 revealed a significant association with the levels of both NFκB-p65 and TNF-α. In conclusion, rs6000782 and rs1799724 variants are potential genetic risk factors for pAIH predisposition, with the former affecting NFκB-p65 and TNF-α levels. Overall, the inflammatory cascade was associated with the degree of liver cell destruction. Clinically, screening and genetic counselling are recommended for relatives of pAIH patients.

Association of STAT4, TGFβ1, SH2B3 and PTPN22 polymorphisms with autoimmune hepatitis

The physiopathology of autoimmune hepatitis (AIH) is complex and still not fully elucidated. The genes localized outside the histocompatibility complex involved in regulation and signal transduction of the immune system SH2B3, TGFβ1, STAT4 and PTPN22 could be associated to the susceptibility and hepatocyte lysis mechanism of this lethal autoimmune disorder.

PATIENTS AND METHODS

We investigated four polymorphic sites in SH2B3 (rs3184504), TGFβ1 (rs1800471), STAT4 (rs7574865) and PTPN22 (rs2476601) in 45 AIH patients and 150 healthy controls from Tunisia using real-time PCR.

RESULTS

Significant associations were found for SH2B3 T allele (OR = 1.861; p = 0.015, pc = 0.366) and PTPN22 A allele (OR = 7.070; p = 0.026; pc = 1.00) and AIH with opposite homozygous being protective against the disease (CC genotype with OR = 0.420, p = 0.025; GG genotype with OR = 0.136, p = 0.025, respectively). No statistically significant associations were found for the TGFβ1 and STAT4 polymorphisms with AIH susceptibility.

CONCLUSION

Our work enlarges information on non-HLA genes that are associated with AIH by focusing in a region of the world that was poorly molecularly characterized for this disease.

Association of TNF-α-308 Polymorphism with Susceptibility to Autoimmune Hepatitis in Tunisians

Autoimmune hepatitis (AIH) is a chronic hepatitis of unknown etiology and several proinflammatory cytokines are implicated in its pathogenesis. The association of TNF-α gene polymorphism with AIH onset is not fully elucidated especially in the Tunisian population. The aim of this study was to determine the association of TNF-α (-308 G > A) polymorphism with AIH susceptibility and with TNF-α expression or clinical manifestations of AIH. A total of 50 AIH patients and 150 controls were included. Evaluation of TNF-α polymorphism was performed by ARMS PCR method. A significantly higher frequence of the AA genotype was found in AIH patients compared to controls (34 vs. 8%, p = 0.00002, OR 5.88). The frequency of the A-allele was significantly higher in patients with AIH compared to controls (55 vs. 37.3%, p = 0.002, OR 2.05). The G-allele was significantly more frequent in healthy controls compared to AIH patients [43 vs. 61.3%, p = 0.001, OR 0.47 (0.3-0.75)]. There was a positive correlation between the A/A genotype and a higher serum expression of TNF-α. The TNF*A allele confer susceptibility to AIH in the Tunisian patients and is associated with increased production of TNF-α. Anti-TNF antibodies could be an alternative to the use of corticotherapy and may avoid the exacerbated immune response in AIH.

[Autoimmune hepatitis in the pediatric age]

In pediatrics, autoimmune hepatitis and sclerosing cholangitis are liver disorders with an immunological damage mechanism. Autoimmune hepatitis is a disease of unknown etiology characterized by interface hepatitis, hypergammaglobulinemia, circulating autoantibodies and a favorable response to immunosuppression. It is an eminently pediatric disease with a prevalent condition in young women. Therapy should be instituted promptly to prevent rapid deterioration, promote remission of disease and long-term survival. The persistent lack of response or lack of adherence to treatment results in terminal liver failure; these patients, and those with fulminant hepatic insufficiency at the time of diagnosis, will require liver transplantation.

Autoimmune Hepatitis in Children

Autoimmune hepatitis (AIH) is an immune-mediated, inflammatory liver disease. Clinical presentation of AIH in children is highly variable. It can present acutely, chronically, or silently. There are two main types of AIH-type 1 and type 2, which are differentiated and defined by the presence of specific autoantibodies. AIH eventually progresses to cirrhosis when left untreated, and occasionally even with treatment. AIH must be suspected and excluded in all children presenting with signs of acute, prolonged, or severe liver disease. The diagnosis of AIH is made by a combination of clinical manifestations, laboratory evaluation, histopathology, and the exclusion of other more common liver diseases. The best outcome for AIH is dependent on early diagnosis as well as early initiation of immunosuppressant therapy. [Pediatr Ann. 2018;47(2):e81-e86.].

rs10499194 polymorphism in the tumor necrosis factor-α inducible protein 3 (TNFAIP3) gene is associated with type-1 autoimmune hepatitis risk in Chinese Han population

Previous studies have found that the polymorphisms of tumor necrosis factor-α induced protein 3 (TNFAIP3) were associated with several autoimmune diseases. However, the role of TNFAIP3 polymorphisms in type-1 autoimmune hepatitis (AIH-1) remained unclear. The present study aimed to clarify the association of TNFAIP3 polymorphisms with AIH-1 risk in a Chinese Han population. The TaqMan SNP genotyping assay was used to determine the distribution of TNFAIP3 polymorphisms in 432 AIH-1 patients and 500 healthy controls. The association of TNFAIP3 polymorphisms and clinical characteristic was further evaluated. Five TNFAIP3 polymorphisms (rs2230926, rs5029939, rs10499194, rs6920220, rs582757) were analyzed in the present study. No significant association could be observed between rs2230926, rs5029939, rs6920220, rs582757 and the susceptibility to AIH-1 in Chinese Han population. Compared with wild-type genotype CC at rs10499194, individuals carrying CT genotype had a significantly increased risk for developing AIH-1 (OR = 2.32, 95%CI 1.44-3.74). Under a dominant model, CT/TT carriers have a 140% increased risk of AIH-1 than CC carriers (OR = 2.40, 95%CI 1.50-3.87). The rs10499194 T allele was also found to be significantly associated with AIH-1 risk (OR = 2.41, 95%CI 1.51-3.82). In addition, higher serum ALT, AST levels and more common cirrhosis were observed in AIH-1 patients with T allele (CT/TT) than those with CC genotype. In conclusion, TNFAIP3 rs10499194 T allele and CT genotype were associated with an increased risk for AIH-1, suggesting rs10499194 polymorphism as a candidate of susceptibility locus to AIH-1.

Lack of association between the CARD10 rs6000782 polymorphism and type 1 autoimmune hepatitis in a Japanese population

BACKGROUND

Previous genome-wide association studies have evaluated the impact of common genetic variants and identified several non-HLA risk loci associated with autoimmune liver diseases. More recent genome-wide association studies and replication analyses reported an association between variants of the CARD10 polymorphism rs6000782 and risk of type 1 autoimmune hepatitis (AIH). In this case-control study, we genotyped 326 Japanese AIH patients and 214 control subjects.

RESULTS

Genomic DNA from 540 individuals of Japanese origin, including 326 patients with type-1 AIH and 214 healthy controls, was analyzed for two single nucleotide polymorphisms (SNPs) in the CARD10 gene. We selected CARD10 rs6000782 SNPs and genotyped these using PCR-RFLP method and direct sequencing. The Chi square test revealed that the rs6000782 variant alle (c) was not associated with the susceptibility for AIH in a Japanese population [p = 0.376, odds ratio (OR) 1.271, 95 % confidence interval (CI) 0.747-2.161] in an allele model. Our data also showed that CARD10 rs6000782 variants were not associated with AIH or with the clinical parameters of AIH.

CONCLUSIONS

In this study we examined an association between rs6000782 SNPs in the CARD10 gene and type-1 AIH. Results showed no significant association of rs62000782 with type-1 AIH in a Japanese population. This study demonstrated no association between CARD10 rs6000782 variants and AIH in a Japanese population.

Human autoimmune diseases: a comprehensive update

There have been significant advances in our understanding of human autoimmunity that have led to improvements in classification and diagnosis and, most importantly, research advances in new therapies. The importance of autoimmunity and the mechanisms that lead to clinical disease were first recognized about 50 years ago following the pioneering studies of Macfarlane Burnett and his Nobel Prize-winning hypothesis of the 'forbidden clone'. Such pioneering efforts led to a better understanding not only of autoimmunity, but also of lymphoid cell development, thymic education, apoptosis and deletion of autoreactive cells. Contemporary theories suggest that the development of an autoimmune disease requires a genetic predisposition and environmental factors that trigger the immune pathways that lead, ultimately, to tissue destruction. Despite extensive research, there are no genetic tools that can be used clinically to predict the risk of autoimmune disease. Indeed, the concordance of autoimmune disease in identical twins is 12-67%, highlighting not only a role for environmental factors, but also the potential importance of stochastic or epigenetic phenomena. On the other hand, the identification of cytokines and chemokines, and their cognate receptors, has led to novel therapies that block pathological inflammatory responses within the target organ and have greatly improved the therapeutic effect in patients with autoimmune disease, particularly rheumatoid arthritis. Further advances involving the use of multiplex platforms for diagnosis and identification of new therapeutic agents should lead to major breakthroughs within the next decade.

Transitioning from Idiopathic to Explainable Autoimmune Hepatitis

Autoimmune hepatitis lacks an identifiable cause, and its diagnosis requires the exclusion of etiologically defined diseases that resemble it. Insights into its pathogenesis are moving autoimmune hepatitis from an idiopathic to explainable disease, and the goal of this review is to describe the insights that are hastening this transition. Two types of autoimmune hepatitis are justified by serological markers, but they also have distinctive genetic associations (DRB1 and DQB1 genes) and autoantigens. DRB1 alleles are the principal susceptibility factors in white adults, and a six amino acid sequence encoded in the antigen-binding groove of class II molecules of the major histocompatibility complex can influence the selection of autoantigens. Polymorphisms, including variants of SH2B3 and CARD10 genes, may affect immune reactivity and disease severity. The cytochrome mono-oxygenase, CYP2D6, is the autoantigen associated with type 2 autoimmune hepatitis, and it shares homologies with multiple viruses that might promote self-intolerance by molecular mimicry. Chemokines, especially CXCL9 and CXCL10, orchestrate the migration of effector cells to sites of injury and are associated with disease severity. Cells of the innate and adaptive immune responses promote tissue damage, and possible deficiencies in the number and function of regulatory T cells may facilitate the injurious process. Receptor-mediated apoptosis is the principal mechanism of hepatocyte loss, and cell-mediated and antibody-dependent mechanisms of cytotoxicity also contribute. Insights that explain autoimmune hepatitis will allow triggering exogenous antigens to be characterized, risk management to be improved, prognostic indices to be refined, and site-specific therapeutic interventions to emerge.

Climatic droplet keratopathy: an old disease in new clothes

Climatic droplet keratopathy (CDK) is an acquired and potentially handicapping cornea degenerative disease that is highly prevalent in certain rural communities around the world. It predominantly affects males over their forties. It has many other names such as Bietti's band-shaped nodular dystrophy, Labrador keratopathy, spheroidal degeneration, chronic actinic keratopathy, oil droplet degeneration, elastoid degeneration and keratinoid corneal degeneration. CDK is characterized by the haziness and opalescence of the cornea's most anterior layers which go through three stages with increasing severity. Globular deposits of different sizes may be histopathologically observed under the corneal epithelium by means of light and electron microscopy. The coalescence and increased volume of these spherules may cause the disruption of Bowman's membrane and the elevation and thinning of the corneal epithelium. The exact aetiology and pathogenesis of CDK are unknown, but they are possibly multifactorial. The only treatment in CDK advanced cases is a corneal transplantation, which in different impoverished regions of the world is not an available option. Many years ago, the clinical and histological aspects of this disease were described in several articles. This review highlights new scientific evidence of the expanding knowledge on CDK's pathogenesis which will open the prospect for new therapeutic interventions.

Molecular cloning, genomic structure, polymorphism and expression analysis of major histocompatibility complex class IIA gene of swamp eel Monopterus albus

Major histocompatibility complex (MHC) class II molecules play an important role in the immune response of vertebrates. In this paper, full-length MHC IIA cDNA was isolated from swamp eel (Monopterus albus) by rapid amplification of cDNA ends PCR. The genomic structure, molecular polymorphism, tissue distribution, and immune response of the MHC IIA gene to bacterial challenge were investigated. The full-length cDNA (GenBank accession No.: KC616308) is 1,509 bp in length including an 83 bp-long 5' untranslated region (UTR) and a 709 bp-long 3' UTR, which encoded a 238 amino acids protein. In the 2,339 bp-long MHC IIA genomic DNA, four exons and three introns were identified. Sequence comparison exhibited that the deduced amino acid sequence shared 27.1-66.3% identity with those of other species. Seven alleles were identified from five healthy individuals. Number of alleles per individual diversified from two to five. Five different 5' UTR sequences and two different 3' UTR sequences from one individual may infer the existence of five loci at least. Real-time quantitative PCR demonstrated that swamp eel MHC IIA transcripts were ubiquitously expressed in ten tissues, but the expression level was distinctly different. Significant changes were observed in liver, spleen, kidney and intestine after challenged with pathogenic bacteria Aeromonas hydrophilia.

Advances in research of autoimmune hepatitis

Autoimmune hepatitis (AIH) is a chronic inflammatory disease of the liver triggered by an immune-mediated attack, characterized by the presence of hypergammaglobulinemia, serum autoantibodies, interface hepatitis on histological examination, and good response to immunosuppressive therapy. In this article, we will review the role of genetic susceptibility, inducing factors, molecular mimicry, liver injury, and immune regulation imbalance in the pathogenesis of AIH. In addition, this article systematically describes the advances in research of AIH in terms of clinical features, serological characteristics, histologic features, diagnosis and therapy.

Association of the HLA locus and TNF with type I autoimmune hepatitis susceptibility in New Zealand Caucasians

Purpose

The precise etiology of autoimmune hepatitis (AIH) remains unknown, although a number of genetic loci have been implicated in the susceptibility of type 1 AIH. The purpose of this study was to test for association of these loci with type 1 AIH in New Zealand Caucasians.

Methods

77 AIH patients and 485 healthy controls were genotyped for the SNPs rs2187668 (HLA-DRB*03:01), rs660895 (HLA-DRB*04:01), rs3749971 (HLA-A1-B8-DR3), rs231775 (CLTLA4), rs1800629 (TNF), and rs1800682 (FAS) using predesigned TaqMan SNP genotyping assays. Chi square analysis was used to test for association of allele and genotype with overall AIH, and with severe fibrosis and ALT levels at 6 months.

Results

Significant risk of AIH was conferred by the minor alleles of rs2187668 (OR = 2.45, 95% CI 1.65-3.61, p < 0.0001), rs3749971 (OR = 1.89, 95% CI 1.21-2.94, p = 0.004) and rs1800629 (OR = 2.06, 95% CI 1.41-3.01, p = 0.0001). Multivariate analysis showed that rs2187668 was independently associated with type 1 AIH susceptibility (OR = 2.40, 95% CI 1.46-3.93, p = 0.001). The C allele of FAS SNP rs1800682 was associated with increased risk of severe fibrosis at diagnosis (OR = 2.03, 95% CI 1.05-3.93, p = 0.035) and with incomplete normalization of ALT levels at 6 months post-diagnosis (OR = 3.94, 95% CI 1.62-9.54, p = 0.0015).

Conclusions

This is the first population-based study to investigate genetic risk loci for type 1 AIH in New Zealand Caucasians. We report significant independent association of HLA-DRB1*03:01 with overall susceptibility to type 1 AIH, as well as FAS with a more aggressive disease phenotype.

Autoimmune hepatitis in childhood: The role of genetic and immune factors

Autoimmune hepatitis (AIH) is a rare chronic inflammatory disease of the liver, which affects a group of patients who lost their immunological tolerance to antigens of the liver. It is clinically characterized by hypergammaglobulinemia, elevated liver enzymes, presence of autoantibodies and histological changes. Although being rare in children, it represents a serious cause of chronic hepatic disease that can lead to cirrhosis and hepatic failure. Clinical findings, exclusion of more common liver disorders and the detection of antibodies antinuclear antibodies, smooth muscle antibodies and anti-LKM1 are usually enough for diagnosis on clinical practice. The pathogenic mechanisms that lead to AIH remain obscure, but some research findings suggest the participation of immunologic and genetic factors. It is not yet knew the triggering factor or factors that stimulate inflammatory response. Several mechanisms proposed partially explain the immunologic findings of AIH. The knowledge of immune factors evolved might result in better markers of prognosis and response to treatment. In this review, we aim to evaluate the findings of research about genetic and immune markers and their perspectives of application in clinical practice especially in pediatric population.