HLA and immunoglobulin polymorphisms in idiopathic dilated cardiomyopathy

Clinical Characteristics and Mechanisms of Acute Myocarditis

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT05335928.

Meeting the Challenges of Myocarditis: New Opportunities for Prevention, Detection, and Intervention—A Report from the 2021 National Heart, Lung, and Blood Institute Workshop

The National Heart, Lung, and Blood Institute (NHLBI) convened a workshop of international experts to discuss new research opportunities for the prevention, detection, and intervention of myocarditis in May 2021. These experts reviewed the current state of science and identified key gaps and opportunities in basic, diagnostic, translational, and therapeutic frontiers to guide future research in myocarditis. In addition to addressing community-acquired myocarditis, the workshop also focused on emerging causes of myocarditis including immune checkpoint inhibitors and SARS-CoV-2 related myocardial injuries and considered the use of systems biology and artificial intelligence methodologies to define workflows to identify novel mechanisms of disease and new therapeutic targets. A new priority is the investigation of the relationship between social determinants of health (SDoH), including race and economic status, and inflammatory response and outcomes in myocarditis. The result is a proposal for the reclassification of myocarditis that integrates the latest knowledge of immunological pathogenesis to refine estimates of prognosis and target pathway-specific treatments.

Autoimmunity in Acute Myocarditis: How Immunopathogenesis Steers New Directions for Diagnosis and Treatment

PURPOSE OF REVIEW

Over the last decade, myocarditis has been increasingly recognized as common cause of sudden cardiac death in young adults and heart failure overall. The purpose of this review is to discuss hypothesis of development of non-infectious myocarditis, to provide a description of the immunopathogenesis and the most common mechanisms of autoimmunity in myocarditis, and to provide an update on therapeutic options.

RECENT FINDINGS

A new entity of myocarditis is immune checkpoint inhibitor (ICI) induced myocarditis. ICIs are used in advanced cancer to "disinhibit" the immune system and make it more aggressive in fighting cancer. This novel drug class has doubled life expectancy in metastatic melanoma and significantly increased progression free survival in advanced non-small-cell lung cancer, but comes with a risk of autoimmune diseases such as myocarditis resulting from an overly aggressive immune system. Myocarditis is an inflammatory disease of the heart with major public health impact. Thorough understanding of its immunopathogenesis is crucial for accurate diagnosis and effective treatment.

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.

A genome-wide association study identifies 6p21 as novel risk locus for dilated cardiomyopathy

AIMS

Dilated cardiomyopathy (DCM) is one of the leading causes for cardiac transplantations and accounts for up to one-third of all heart failure cases. Since extrinsic and monogenic causes explain only a fraction of all cases, common genetic variants are suspected to contribute to the pathogenesis of DCM, its age of onset, and clinical progression. By a large-scale case-control genome-wide association study we aimed here to identify novel genetic risk loci for DCM.

METHODS AND RESULTS

Applying a three-staged study design, we analysed more than 4100 DCM cases and 7600 controls. We identified and successfully replicated multiple single nucleotide polymorphism on chromosome 6p21. In the combined analysis, the most significant association signal was obtained for rs9262636 (P = 4.90 × 10(-9)) located in HCG22, which could again be replicated in an independent cohort. Taking advantage of expression quantitative trait loci (eQTL) as molecular phenotypes, we identified rs9262636 as an eQTL for several closely located genes encoding class I and class II major histocompatibility complex heavy chain receptors.

CONCLUSION

The present study reveals a novel genetic susceptibility locus that clearly underlines the role of genetically driven, inflammatory processes in the pathogenesis of idiopathic DCM.

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.

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.

Autoimmune cardiomyopathy and heart block develop spontaneously in HLA-DQ8 transgenic IAbeta knockout NOD mice

A line of nonobese diabetic (NOD) mice expressing the human diabetes-associated HLA-DQ8 transgene in the absence of mouse IAbeta failed to show spontaneous insulitis or diabetes, but rather developed dilated cardiomyopathy, leading to early death from heart failure. Pathology in these animals results from an organ- and cell-specific autoimmune response against normal cardiomyoctes in the atrial and ventricular walls, as well as against very similar myocytes present in the outermost muscle layer surrounding the pulmonary veins. Progression of the autoimmune process could be followed by serial ECG measurements; irradiation of young animals significantly delayed disease progression, and this effect could be reversed by adoptive transfer of splenocytes taken from older animals with complete heart block. Disease progression could also be blocked by cyclosporin A treatment, but was accelerated by injection of complete Fruend's adjuvant. The constellation of findings of spontaneously arising destructive focal lymphocytic infiltrates within the myocardium, rising titers of circulating anticardiac autoantibodies, dilation of the cardiac chambers, and gradual progression to end-stage heart failure bears a striking resemblance to what is seen in humans with idiopathic dilated cardiomyopathy, a serious and often life-threatening medical condition. This transgenic strain provides a highly relevant animal model for human autoimmune myocarditis and postinflammatory dilated cardiomyopathy.

Generation of humanized mice susceptible to peptide-induced inflammatory heart disease

BACKGROUND

Dilated cardiomyopathy (DCM) is a major cause of sudden cardiac death. In certain mouse major histocompatibility complex (MHC) backgrounds, myocarditis and inflammatory cardiomyopathy can be triggered by immunization with heart muscle-specific proteins. Similarly, chronic heart disease in humans has been linked to certain HLA alleles, such as HLA-DQ6. However, there is no experimental evidence showing that human MHC class II molecules and peptides derived from human proteins are involved in the pathogenesis of myocarditis and DCM.

METHODS AND RESULTS

We generated double CD4- and CD8-deficient mice transgenic for human CD4 (hCD4) and human HLA-DQ6 to specifically reconstitute the human CD4/DQ6 arm of the immune system in mice. Transgenic hCD4 and HLA-DQ6 expression rendered genetically resistant C57BL/6 mice susceptible to the induction of autoimmune myocarditis induced by immunization with cardiac myosin. Moreover, we identified heart-specific peptides derived from both mouse and human alpha-myosin heavy chains capable of inducing inflammatory heart disease in hCD4 and HLA-DQ6 double transgenic mice but not in hCD4 single transgenic littermates. The autoimmune inflammatory heart disease induced by the human heart muscle-specific peptide in hCD4 and HLA-DQ6 double transgenic mice shared functional and phenotypic features with the disease occurring in disease-susceptible nontransgenic mice.

CONCLUSIONS

Our data provide the first genetic and functional evidence that human MHC class II molecules and a human alpha-myosin heavy chain-derived peptide can cause inflammatory heart disease and suggest that human inflammatory cardiomyopathy can be caused by organ-specific autoimmunity. The humanized mice generated in this study will be an ideal animal model to further elucidate the pathogenesis of inflammatory heart disease and facilitate the development of rational treatment strategies.

Cardiac autoimmunity in HIV related heart muscle disease

OBJECTIVE

To assess the frequency of circulating cardiac specific autoantibodies in HIV positive patients with and without echocardiographic evidence of left ventricular dysfunction.

SUBJECTS

74 HIV positive patients including 28 with echocardiographic evidence of heart muscle disease, 52 HIV negative people at low risk of HIV infection, and 14 HIV negative drug users who had all undergone non-invasive cardiac assessment were studied along with a group of 200 healthy blood donors.

RESULTS

Cardiac autoantibodies detected by indirect immunofluorescence (serum dilution 1/10) were more common in the HIV positive patients (15%), particularly the HIV heart muscle disease group (21%), than in HIV negative controls (3.5%) (both p < 0.001). By ELISA (dilution 1/320), abnormal anti-alpha myosin autoantibody concentrations were found more often in HIV patients with heart muscle disease (43%) than in HIV positive patients with normal hearts (19%) or in HIV negative controls (3%) (p < 0.05 and p < 0.001, respectively). Anti-alpha myosin autoantibody concentrations were greater in HIV positive patients than in HIV negative controls, regardless of cardiac status ((mean SD) 0.253 (0.155) v 0.170 (0.076); p = 0.003). In particular the mean antibody concentration was higher in the HIV heart muscle disease patients (0.291 (0.160) v 0.170 (0.076); p = 0.001) than in HIV negative controls. On follow up, six subjects with normal echocardiograms but raised autoantibody concentrations had died after a median of 298 days, three with left ventricular abnormalities at necropsy. This compared with a median survival of 536 days for 21 HIV positive patients with normal cardiological and immunological results.

CONCLUSIONS

There is an increased frequency of circulating cardiac specific autoantibodies in HIV positive individuals, particularly those with heart muscle disease. The data support a role for cardiac autoimmunity in the pathogenesis of HIV related heart muscle disease, and suggest that cardiac autoantibodies may be markers of the development of left ventricular dysfunction in HIV positive patients with normal hearts.

Idiopathic dilated cardiomyopathy: familial prevalence and HLA distribution

OBJECTIVES

To compare HLA distribution in familial and non-familial dilated cardiomyopathy, because a serum marker that could identify families at risk of developing dilated cardiomyopathy should be of use in screening for the disease.

PATIENTS

100 patients with dilated cardiomyopathy.

METHODS

200 first degree relatives from 56 of the proband families were screened for dilated cardiomyopathy by echocardiography. The HLA profile of the patients with dilated cardiomyopathy, as well as of the familial and non-familial subgroups, was compared with that of 9000 normal controls.

RESULTS

The familial prevalence of dilated cardiomyopathy in this patient group was "definite" in 14 of 56 (25%) and "possible" in 25 of 56 (45%). The HLA-DR4 frequency in the 100 patients with dilated cardiomyopathy was similar to that in the 9000 controls (39% v 32%). However, the DR4 subtype was significantly more common in the 25 probands with a familial tendency to dilated cardiomyopathy than in the 31 probands with non-familial dilated cardiomyopathy (68% v 32%; P < 0.05).

CONCLUSIONS

The present finding supports an HLA linked predisposition to familial dilated cardiomyopathy. The HLA type DR4 was significantly more common in familial than in non-familial cases. The DR4 halotype was associated with two thirds of the families at risk for dilated cardiomyopathy.

Evidence for autoimmunity to myosin and other heart-specific autoantigens in patients with dilated cardiomyopathy and their relatives

Autoimmune disease is characterised by the presence of circulating autoantibodies in the affected patients and in a proportion of their relatives. These antibodies are generally not pathogenic but are reliable markers of immune-mediated tissue damage. In organ-specific autoimmune disease, the destruction process is largely restricted to one organ within the body and the autoantibodies react with autoantigens which are unique to the diseased target organ. At least in a patient subset, myocarditis and dilated cardiomyopathy (DCM) may represent the acute and chronic stages of a progressive organ-specific autoimmune disease of the myocardium. Autoimmune features in patients with myocarditis/DCM include: familial aggregation, a weak association with HLA-DR4, abnormal expression of HLA class II on cardiac endothelium on endomyocardial biopsy, and detection of organ- and disease-specific cardiac autoantibodies, by immunofluorescence and absorption techniques, in the affected patients and in a proportion of their symptom-free relatives from both familial and non-familial DCM pedigrees. The organ-specific cardiac autoantibodies detected by immunofluorescence are directed against multiple antigens. One of these, first identified using immunoblotting and confirmed by ELISA, is the cardiac-specific alpha-myosin isoform. Myosin fulfils the expected criteria for organ-specific autoimmunity, in that immunisation with cardiac but not skeletal myosin reproduces, in susceptible mouse strains, the human disease phenotype of DCM; in addition, alpha-myosin is entirely cardiac-specific and is only expressed in the myocardium. Using ELISA, high titer organ- and disease-specific anti alpha-myosin antibodies have been found in 16% of the symptom-free relatives of DCM patients and in 38% of the pedigrees of the same cohort of relatives studied by immunofluorescence. The ELISA results provide additional evidence for autoimmunity in a subset of DCM families, and emphasise the importance of alpha-myosin as a target antigen.

Fatal Epstein-Barr virus myocarditis in a child with repetitive myocarditis

Fatal Epstein-Barr virus (EBV) myocarditis occurred in a 9-year-old female with a history of two prior discrete episodes of myocarditis, the first associated with chicken pox and the second of undetermined origin. Serologic studies during the fatal episode were characteristic of acute EBV infection, and EBV genome was detected by polymerase chain reaction (PCR) amplification of DNA extracted from autopsy heart and liver. PCRs for enteroviruses and cardiac viral culture were negative. An intense mononuclear cell infiltrate in the myocardium consisted entirely of T cells, without identifiable B cells. Human leukocyte antigen HLA-DR analysis using frozen tissue obtained postmortem revealed antigens DR4 and DR13. DR4 is associated with some autoimmune disorders, as well as idiopathic dilated cardiomyopathy. We postulate that an aberrant immune response, possibly associated with the DR4 locus, was responsible for the repetitive episodes of myocarditis in this patient.

Immunoglobulin allotypes (GM and KM) and their interactions with HLA antigens in autoimmune diseases: a review

GM and KM immunoglobulin (Ig) allotypes and their interactions with HLA antigens have been analyzed in various autoimmune diseases: multiple sclerosis, rheumatoid arthritis, insulin-dependent diabetes mellitus (IDDM), systemic lupus erythematosus, coeliac disease, Crohn's disease, Graves' disease, atrophic thyroiditis, Hashimoto's thyroiditis, myasthenia gravis, chronic active hepatitis, alopecia areata, uveitis, vitiligo, Turner's syndrome, glomerular nephritis, Berger's disease and idiopathic dilated cardiomyopathy. This review reports published results about associations or linkages, as well as the origins of the populations, the numbers of patients and controls tested. The possible role of Ig polymorphisms in the physiopathology of autoimmune diseases is discussed. Ig allotypes and statistical methods used to analyse the HLA and Ig data are also described.

Absence of linkage between idiopathic dilated cardiomyopathy and candidate genes involved in the immune function in a large Italian pedigree

Idiopathic dilated cardiomyopathy (IDC) is a heart disease of unknown aetiology characterised by impaired ventricular function usually associated with dilatation of the cardiac chambers. In order to test the hypothesis of an immunological cause for the disease at the genetic level, we performed linkage analysis between the putative disease locus and some of the potential candidate genes involved in the immune response or coding for the targets for autoantibodies in a large multigeneration family (63 members) from southern Italy with autosomal dominant transmission of the disease. Twenty-nine polymorphic markers on 18 different chromosomal locations were investigated, including markers linked to the genes coding for the HLA antigens, the immunoglobulin heavy and light chains, the receptors for the immunoglobulin Fc fragments, the subunits of the T cell receptor and the associated CD3, CD4, CD8, and CD45 antigens, interleukins 1, 3, 4, 5, 6, 9, and 11, the interleukin 1 and 2 receptors, and the genes coding for the beta 1 adrenoreceptor, the adenine nucleotide translocator-1, and the cardiac alpha and beta myosin heavy chains. No evidence for genetic linkage to IDC was found at any of these candidate loci. These results indicate that the still unidentified IDC gene maps outside several loci involved in the regulation of immune reactivity.

Non-MHC-linked genes in autoimmune diseases

Single-locus mutations in mice associated with autoimmune manifestations or influencing them, including lpr, motheaten and xid have been characterized at the molecular level. Mutations have been described in the genes encoding Fc gamma RI, interleukin-2 and natural resistance associated macrophage protein, which are all candidate genes for susceptibility loci associated with autoimmune diabetes in non-obese diabetic mice. Twelve regions of DNA that are associated with disease susceptibility have now been identified in this polygenic model of autoimmunity. In human autoimmune diseases, the region of DNA surrounding the insulin gene that is associated with susceptibility to insulin dependent diabetes mellitus has been narrowed down to 4.1 kilobases.