MHC class II genes in Mexican patients with idiopathic dilated cardiomyopathy

Identification of key immune-related genes in dilated cardiomyopathy using bioinformatics analysis

Dilated cardiomyopathy (DCM) is characterized by the left ventricular dilatation and impaired myocardial systolic dysfunction with high mortality and morbidity. However, the underlying mechanisms remain elusive. We first identified the differentially expressed genes (DEGs) between the DCM and control group using two expression profiles from GSE3585 and GSE84796. Enrichment analysis was conducted to explore the potential mechanisms underlying DCM. A total of four algorithms, including key module of MCODE, degree, maximum neighborhood component (MNC), and maximal clique centrality (MCC), were used to identify the hub genes within Cytoscape. The correlation between hub genes and infiltrated immune cells was evaluated to determine potential immune-related genes. The expression analysis and diagnosis value analysis of potential immune-related genes were performed. Finally, the expression analysis with GSE57338 and relationship analysis with the comparative toxicogenomics database (CTD) were performed to identify the key immune-related genes in DCM. A total of 80 DEGs were screened for DCM. Enrichment analysis revealed that DEGs were involved in the immune-related pathological process. Immune infiltration analysis indicated a potentially abnormal immune response in DCM. Four up-regulated genes (COL1A2, COL3A1, CD53, and POSTN) were identified as potential immune-related genes. Finally, three genes (COL1A2, COL3A1, and POSTN) were determined as the key immune-related genes in DCM via expression analysis with a validation set (GSE57338) and relationship analysis with CTD. Our study suggested that the upregulated COL1A2, COL3A1, and POSTN might be the key immune-related genes for DCM. Further studies are needed to validate the underlying mechanisms.

Susceptible loci associated with autoimmune disease as potential biomarkers for checkpoint inhibitor-induced immune-related adverse events

Unprecedented successes regarding cancer immunotherapy have been achieved, in which therapeutic agents are used to target immune cells rather than cancer cells. The most effective immunotherapy to date is the group of immune checkpoint inhibitors (CPI), targeting, for example, cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) or programmed cell death protein (PD-1). TThe combination of these therapies (anti-PD-1 with anti-CTLA-4) induces high response rates, and seem to be increased further when applied in early-stage disease. However, combined CTLA-4 plus PD-1 blockade causes frequent high-grade immune-related adverse events (irAE). To date, research on biological mechanism of irAEs is scarce and no widely accepted biomarkers predicting onset of severe irAEs have been identified. The similarity of irAEs to autoimmune disorders fuels the hypothesis that irAEs may be linked to susceptible genetic loci related to various autoimmune diseases. In this review, we extensively searched for susceptible loci associated with various autoimmune diseases, and pooled them in groups most likely to be associated with CPI-induced irAEs. These sets could be used in future research on predicting irAEs and guide physicians in a more refined and personal manner.

Cardiac Autoimmunity: Myocarditis

Myocarditis is the inflammation of the muscle tissues of the heart (myocardium). After a pathologic cardiac-specific inflammatory process, it may progress to chronic damage and dilated cardiomyopathy. The latter is characterized by systolic dysfunction, whose clinical correlate is heart failure. Nevertheless, other acute complications may arise as consequence of tissue damage and electrophysiologic disturbances. Different etiologies are involved in triggering myocarditis. In some cases, such as giant cell myocarditis or eosinophilic necrotizing myocarditis, it is an autoimmune process. Several factors predispose the development of autoimmune myocarditis such as systemic/local primary autoimmunity, viral infection, HLA and gender bias, exposure of cryptic antigens, mimicry, and deficient thymic training/Treg induction. Once the anti-myocardium autoimmune process is triggered, several components of the immune response orchestrate a sustained attack toward myocardial tissues with particular timing and immunopathogenic features. Innate response mediated by monocytes/macrophages, neutrophils, and eosinophils parallels the adaptive response, playing a final effector role and not only a priming function. Stromal cells like fibroblast are also involved in the process through specific cytokines. Furthermore, adaptive T cell responses have anti-paradigmatic features, as Th17 response is dispensable for acute myocarditis but is the main driver of the process leading to dilated cardiomyopathy. Humoral response, thought to be a bystander, is important in the appearance of late-stage hemodynamic complications. The complexity of that process, as well as the unspecific and variable clinical presentation, had generated difficulties for diagnosis and treatment, which remain suboptimal. In this chapter, we will discuss the most relevant immunopathogenic findings from a basic science and clinical perspective.

HLA-DR3 antigen in the resistance to idiopathic dilated cardiomyopathy

Idiopathic dilated cardiomyopathy (IDC) has been hypothesized as a multifactorial disorder initiated by an environment trigger in individuals with predisposing human leukocyte antigen (HLA) alleles. Published data on the association between HLA-DR3 antigen and IDC risk are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed. Studies were identified by searching the PUBMED and Embase database (starting from June 2015). A total of 19 case-control studies including 1378 cases and 10383 controls provided data on the association between HLA-DR3 antigen and genetic susceptibility to IDC. Overall, significantly decreased frequency of HLA-DR3 allele (OR=0.72; 95%CI=0.58-0.90; P=0.004) was found in patients with IDC compared with controls. When stratified by myocardial biopsy or non-biopsy cases, statistically decreased risk was found for IDC in myocardial biopsy cases (OR=0.69; 95%CI=0.57-0.84; P=0.0003). In the subgroup analysis by ethnicity, borderline statistically significantly decreased risk was found among Europeans from 12 case-control studies (OR=0.76; 95%CI=0.58-1.00; P=0.05). In conclusion, our results suggest that individuals with HLA-DR3 antigen may have a protective effect against IDC.

Human leukocyte antigen-DQ beta 1 chain (DQB1) gene polymorphisms are associated with dilated cardiomyopathy: a systematic review and meta-analysis

BACKGROUND

Previous studies reported an association between the human leukocyte antigen (HLA)-DQ antigen beta 1 chain (DQB1) alleles and dilated cardiomyopathy (DCM). However, the results of those studies have been inconsistent. To clarify the association between HLA-DQB1 and DCM, we performed a systematic review and meta-analysis of case-control studies.

METHODS

Searches were performed using the PubMed database, the Excerpta Medica Database (EMBASE), the Cochrane Central Register of Controlled Trials database, the Science Citation Index database, the China Biology Medicine disc, the China National Knowledge Information database, the Wanfang database, and the Chinese Scientific and Technological Journal Database (VIP database). The search terms included "dilated cardiomyopathy" and "DQB1." Ten case-controlled studies were included in the systematic review to assess the association between DCM and the HLA-DQB1*0201, *0302, *0504, *0301, and *0602 alleles.

RESULTS

In total, 8 studies were included in the meta-analysis of the HLA-DQB1 *0201 allele. The pooled odds risk (OR) for this allele was .47, with a 95% confidence interval (CI) of .28 to .77 (P < .01). With respect to the HLA-DQB1 *0504 allele, only 3 studies were included in our meta-analysis. The pooled OR was .36 (95% CI, .15 to .84; P < .05). Nine, 8, and 7 studies of the HLA-DQB1 *0301, *0302, and *0602 alleles, respectively, were included in our meta-analysis. No statistically significant difference was evident in the frequency of these 3 alleles between the DCM and normal control groups.

CONCLUSION

The HLA-DQB1 *0201 and *0504 alleles may be protective against DCM.

HLA-DRB1 gene polymorphism is associated with idiopathic dilated cardiomyopathy: a meta-analysis

OBJECTIVE

Some studies have reported that the HLA-DRB1 allele was associated with idiopathic dilated cardiomyopathy. However, there have been inconsistent results among different studies. To clarify the association of HLA-DRB1 and idiopathic dilated cardiomyopathy, a meta-analysis of case-control studies was performed.

METHODS

PubMed database, Science Citation Index database, The Cochrane Central Register of Controlled Trials database, China National Knowledge Information database, Chinese Biomedical Literature database, Wanfang database, and VIP database in China were searched. Search terms included dilated cardiomyopathy and DRB1. Five case-control studies were included in the present meta-analysis to assess the association between HLA-DRB1*1401, HLA-DRB1*0901, HLA-DRB1*0301, and idiopathic dilated cardiomyopathy.

RESULTS

A total of four studies were included in our meta-analysis for HLA-DRB1*1401 and HLA-DRB1*0901. The pooled odds ratio (OR) was 2.6 [95% confidence interval (CI) 1.11-6.11, P<0.05] and 0.70 (95% CI 0.48-1.00, P=0.05), respectively. For the HLA-DRB1*0301 allele, just three studies were included in our meta-analysis. The pooled OR was 0.49 (95% CI 0.27-0.91, P<0.05). The present meta-analysis indicated that the frequency of HLA-DRB1*1401 was higher in idiopathic dilated cardiomyopathy patients than in healthy people, whereas HLA-DRB1*0901 and HLA-DRB1*0301 were higher in healthy people than in idiopathic dilated cardiomyopathy patients.

CONCLUSION

The HLA-DRB1*1401 allele might be a risk factor for idiopathic dilated cardiomyopathy and HLA-DRB1*0901 and HLA-DRB1*0301 might protect humans from idiopathic dilated cardiomyopathy.

A meta-analysis of HLA-DR polymorphism and genetic susceptibility to idiopathic dilated cardiomyopathy

Idiopathic dilated cardiomyopathy (IDC) has been hypothesized as a multifactorial disorder initiated by an environment trigger in individuals with predisposing human leukocyte antigen (HLA) alleles. Published data on the association between HLA-DR polymorphism and IDC risk are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed. A total of 19 case-control studies including 1,378 cases and 10,383 controls provided data on the association between HLA-DR polymorphism and genetic susceptibility to IDC. Overall, statistically elevated frequencies of HLA-DR4 (OR 1.58; 95% CI 1.21-2.07; P=0.0009) and HLA-DR5 (OR 1.35; 95% CI 1.05-1.73; P=0.02) alleles were found in patients with IDC compared with controls. Individuals with HLA-DR3 antigen have a protective effect against IDC (OR 0.72; 95% CI 0.58-0.90; P=0.004). In summary, this meta-analysis indicated that certain HLA-DR alleles may be genetic markers for susceptibility and resistance to IDC.

Dilated cardiomyopathy

Dilated cardiomyopathy is characterised by left ventricular dilation that is associated with systolic dysfunction. Diastolic dysfunction and impaired right ventricular function can develop. Affected individuals are at risk of left or right ventricular failure, or both. Heart failure symptoms can be exercise-induced or persistent at rest. Many patients are asymptomatic. Chronically treated patients sometimes present acutely with decompensated heart failure. Other life-threatening risks are ventricular arrhythmias and atrioventricular block, syncope, and sudden death. Genetic inheritance arises in 30-48% of patients, and inflammatory disorders such as myocarditis or toxic effects from medications, alcohol, or illicit drugs also result in dilated cardiomyopathy. Genes that cause dilated cardiomyopathy generally encode cytoskeletal and sarcomeric (contractile apparatus) proteins, although disturbance of calcium homeostasis also seems to be important. In children, disrupted mitochondrial function and metabolic abnormalities have a causal role. Treatments focus on improvement of cardiac efficiency and reduction of mechanical stress. Arrhythmia therapy and prevention of sudden death continue to be mainstays of treatment. Despite progress over the past 10 years, outcomes need to be improved.

HLA class II polymorphisms in Tunisian patients with dilated cardiomyopathy

Cardiomyopathies (CMs) are primary disorders of cardiac muscle. They are a major cause of morbidity and mortality for all ages and, like acquired forms of cardiovascular disease, often result in heart failure. Molecular genetic studies have made remarkable progress in defining the pathogenesis of CM. The present study was the first report to evaluate the relationship between class II major histocompatibility complex (MHC) genes (HLA-DRB1 and HLA-DQB1) and the genetic susceptibility to primary dilated cardiomyopathy (DCM) in Tunisian patients. The human leukocyte antigen (HLA)-DRB1 and -DQB1 alleles were analyzed in 76 patients with primary DCM and 111 ethnically matched healthy controls using polymerase chain reaction-sequence specific primers technique. An increased frequencies of HLA-DRB1*0401 (OR = 2.67, P < 0.001), HLA-DQB1*0302 (OR = 3.28, P = 0.001) and HLA-DQB1*0401 (OR = 6.26, P = 0.005) alleles were found in the patients with primary DCM compared with healthy controls. Individuals with HLA-DRB1*1301 (OR = 0.24, P < 0.001) and HLA-DQB1*0201 (OR = 0.49, P = 0.002) alleles have a protective effect against primary DCM. Two haplotypes were associated with increased risk of primary DCM: DRB1*0401/DQB1*0302 (OR = 4.53, P = 0.002) and DRB1*0401/DQB1*0401 (OR = 9.42, P = 0.004). In conclusion, our data suggest that the variation in class II HLA alleles could be a genetic factor involved in the susceptibility to primary DCM in the Tunisian population.

Pathogenesis of myocarditis and dilated cardiomyopathy

Myocarditis is a disease with a variable clinical presentation, ranging from asymptomatic to a fatal outcome. Among the recognized causes of myocarditis are mutations in multiple genes; infection by bacterial, rickettsial, mycotic, protozoan, and viral agents; and exposure to drugs, toxins, and alcohol. Some subtypes of myocarditis, such as giant cell myocarditis or eosinophilic necrotizing myocarditis, are suspected to be caused by an autoimmune inflammation. Several lines of evidence support the involvement of autoimmunity in myocarditis. These include the production of antibodies against relevant self-antigens, the fact that myocarditis symptoms can be relieved by immunosuppressive therapy in some patients, and a co-occurrence of myocarditis with other autoimmune diseases. Most of the evidence that myocarditis is an autoimmune disease comes from animal models. In this chapter, we discuss coxsackievirus B3-induced myocarditis and myosin-induced myocarditis as models of both viral and autoimmune inflammation in the heart. The latest advances in the study of autoimmunity have been concentrated on T helper cells, particularly the newly discovered subset, Th17 cells. Experimental autoimmune myocarditis (EAM), a mouse model of myocarditis induced by cardiac myosin, is partly an IL-17-driven disease. However, we have shown recently in IL-13 knockout mice that the disease can be driven through other pathways, and that the Th1 helper cells also lead to severe heart inflammation. Most importantly, IL-17A knockout mice are not fully protected against EAM and still develop mild myocarditis. The most abundant cells in heart infiltrate in human giant cell myocarditis or EAM are monocyte/macrophages, and there is now evidence that macrophages play a decisive role in the course of EAM.

Genetic complexity of autoimmune myocarditis

Autoimmune myocarditis, a chronic stage of myocardial inflammation, occurs in a small subset of patients after acute cardiotropic viral infection and can lead to dilated cardiomyopathy (DCM). This disease can be recapitulated in susceptible mouse strains by infection with coxsackievirus B3, or by immunization with cardiac myosin or cardiac troponin I. The etiologies of myocarditis are multifactorial and genetically complex. Genetic linkage between susceptibility to myocarditis/DCM and the major histocompatibility complex (MHC) genes has been reported in both humans and experimentally induced mouse models. However, unlike other autoimmune diseases, the non-MHC genes seem to have greater impact than MHC genes on disease susceptibility. Several myocarditis-related non-MHC loci have been identified by our laboratory and others in different models. Most of these loci overlap with other autoimmune disease susceptibility loci, suggesting common or shared genetic traits influencing general autoimmunity. For example, we have demonstrated that Eam1 and Eam2 may influence disease susceptibility via regulating T cell apoptosis at different developmental stages. Blockade of signaling through specific genes, such as CTLA4, ICOS and PD-1, can either enhance or prevent the development of experimental autoimmune myocarditis, but it remains unclear whether functional polymorphisms in these genes are involved in predisposition to disease. In humans, mutations/deletions in immunologically important genes such as CD45, and genes encoding cardiac proteins, have been reported in patients with recurrent myocarditis or DCM. Identification of genetic polymorphisms controlling autoimmune myocarditis will help us understand the mechanisms underlying autoimmune diseases in general, thereby improving potential therapies in patients.

Contemporary trends in the epidemiology and management of cardiomyopathy and pericarditis in sub-Saharan Africa

Heart failure in sub-Saharan Africans is mainly due to non-ischaemic causes, such as hypertension, rheumatic heart disease, cardiomyopathy and pericarditis. The two endemic diseases that are major contributors to the clinical syndrome of heart failure in Africa are cardiomyopathy and pericarditis. The major forms of endemic cardiomyopathy are idiopathic dilated cardiomyopathy, peripartum cardiomyopathy and endomyocardial fibrosis. Endomyocardial fibrosis, which affects children, has the worst prognosis. Other cardiomyopathies have similar epidemiological characteristics to those of other populations in the world. HIV infection is associated with occurrence of HIV-associated cardiomyopathy in patients with advanced immunosuppression, and the rise in the incidence of tuberculous pericarditis. HIV-associated tuberculous pericarditis is characterised by larger pericardial effusion, a greater frequency of myopericarditis, and a higher mortality than in people without AIDS. Population-based studies on the epidemiology of heart failure, cardiomyopathy and pericarditis in Africans, and studies of new interventions to reduce mortality, particularly in endomyocardial fibrosis and tuberculous pericarditis, are needed.

14 bp deletion polymorphism in the HLA-G gene is a risk factor for idiopathic dilated cardiomyopathy in a Chinese Han population

Human leukocyte antigen (HLA) has been reported to be associated with the pathogenesis of autoimmune-associated idiopathic dilated cardiomyopathy (IDC). However, the HLA-G in this context is limited. In the current study, a total of 117 IDC patients and age and sex matched 401 unrelated healthy controls in a Chinese Han population were HLA-G genotyped for the 14 bp insertion and deletion polymorphism. IDC patients showed markedly increased frequencies of -14 bp/-14 bp genotype [Pc = 0.00049, odds ratio (OR) = 2.17] and -14 bp alleles (Pc = 4.1 x 10(-5), OR = 1.97) when compared with healthy controls. Whereas the frequencies of +14 bp/+14 bp genotype (Pc = 0.0036, OR = 0.35) and +14 bp alleles (Pc = 4.1 x 10(-5), OR = 0.51) were significantly lower in IDC. These data, for the first time, indicated that 14 bp insertion/deletion polymorphism in HLA-G gene could be a genetic risk factor for the susceptibility to IDC.