T-cell receptor gene polymorphisms in familial cardiomyopathy: correlation with anti-beta-receptor autoantibodies

HLA-DQA1, -DQB1 Polymorphism and Genetic Susceptibility to Idiopathic Dilated Cardiomyopathy in Hans of Northern China

Autoimmune mechanisms are likely to participate in the pathogenesis of at least a subgroup of idiopathic dilated cardiomyopathy (IDC), and components of the major histocompatibility complex (MHC) may serve as markers for the propensity to develop immune-mediated myocardial damage. Human leukocyte antigen (HLA) class II genes, especially HLA-DQ genes, which are highly polymorphic, play an important role in the activation of immune responses and thus control the predisposition to, or protection from, IDC. This study was conducted to investigate the association of HLA-DQA1, -DQB1 allele polymorphisms with an autoantibody against the myocardial mitochondria ADP/ATP carrier, and to explore susceptibility to idiopathic dilated cardiomyopathy (IDC) among the Han ethnic group in northern China and the immunological mechanisms and hereditary susceptibility to IDC. Polymerase chain reaction sequence-specific primer (PCR-SSP) techniques were used to analyze polymorphisms of the second exon of HLA-DQA1 and -DQB1 alleles among 68 unrelated IDC patients, 4 probands of IDC pedigrees, and 100 healthy controls, all of Han nationality and having lived in northern China for a long time. Following echocardiography examination the IDC subjects were stratified according to ejection fraction (EF) values. Those with EF values higher than 50% were placed in subgroup 1, subgroup 2 included the patients with an EF value of 15-35%, and subgroup 3 consisted of those whose EF values were less than 15%. An autoantibody against the myocardial mitochondria ADP/ATP carrier was examined using immunoblot analysis. The frequencies of HLA-DQA1*0501 and HLA-DQB1*0303 were 0.3889 and 0.1806 in the IDC group, significantly higher than those of the healthy controls (0.0900 and 0.0364 respectively, both P < 0.05). The OR was 5.20 (95% CI: 3.60-8.50) and 4.85 (95% CI: 2.56-9.39) respectively. Further analysis of the three subgroups showed a higher frequency of HLA-DQA1*0501 among patients whose EF was less than 15% than those whose EF values were > or =15%. Conversely, the frequencies of HLA-DQA1*0201 and -DQB1*0502, *0504 were significantly lower in the IDC group (0.0139, 0.0139 and 0.0417 respectively) than in the control group (0.2000, 0.0727 and 0.1091 respectively) (P < 0.05). The frequency of the HLA-DQA1*0501 allele was significantly higher in IDC patients whose autoantibody is positive in contrast with those whose autoantibody is negative (18.57% vs. 5.86%, P < 0.05); the relative risk (RR) was 4.32. The other frequencies of HLA-DQA1 and -DQB1 alleles showed no significant difference in the antibody positive and negative groups of IDC patients. The alleles of HLA-DQA1*0501 and HLA-DQB1*0303 were closely associated with poor EF values in the IDC group, and may be involved in susceptibility to the disease. The DQA1*0201 and DQB1*0502, *0504 alleles may confer protection to IDC among individuals of northern Chinese Han nationality. The SER(57) residue in the second exon of DQB1*0502 and *0504 may confer resistance to IDC, and defects or substitution of this amino acid residue at position 57 of the DQbeta chain may be associated with IDC susceptibility. HLA-DQ allele polymorphisms may serve as genetic markers for IDC and be involved in the regulation of the immune specific response to auto or exterior anti-myocardium antibodies.

Familial clustering of autoimmune diseases in patients with dilated cardiomyopathy

In this study, we examined the hypothesis that dilated cardiomyopathy (DCM) shares genetic risk factors with other diseases of presumed autoimmune etiology, and, therefore, the same multiple genes in combination with environmental factors lead to numerous different autoimmune diseases. In accordance with this hypothesis, we showed an increased prevalence of autoimmune diseases in first-degree relatives of patients with DCM. Also, T-cell activation, as reflected in high levels of the soluble interleukin-2 receptor, appears to identify patients with DCM with a clustering of autoimmune diseases.

A formidable challenge: the diagnosis and treatment of viral myocarditis in children

It is generally well accepted that one third of patients with viral myocarditis experience a complete recovery of normal cardiac function, one third improve clinically but show residual cardiac dysfunction, and one third experience chronic heart failure and die or require heart transplantation. It is hoped that a better understanding of the underlying cause and pathogenesis of this disease will increase the number of patients who experience a complete recovery. New advances in both the diagnosis and treatment of viral myocarditis continue to enter clinical practice at a rapid pace, and it is likely that a genomic approach to the diagnostic evaluation and treatment of this disease will become possible in the near future. Viral myocarditis, however, will remain a significant diagnosticand therapeutic challenge to both physicians and scientists alike.

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.

Autoimmunity in dilated cardiomyopathy and the major histocompatibility complex

Autoimmune mechanisms are likely to participate in the pathogenesis of a subgroup of dilated cardiomyopathy. These mechanisms involve the elaboration of autoantibodies against cardiac proteins as well as abnormal lymphocyte regulation. The presence of autoantibodies against beta-adrenoceptors correlates with the human leukocyte antigen (HLA)-DR4/1 phenotypes and specific T-cell receptor haplotypes. In addition, histidine at position 36 of the HLA-DQ beta 1 gene is associated with the presence of clinically manifest dilated cardiomyopathy. Components of the major histocompatibility complex (MHC) may thus serve as markers for the propensity to develop immune-mediated myocardial damage.

Exclusion of a primary gene defect at the HLA locus in familial idiopathic dilated cardiomyopathy

Case control studies have reported associations between specific HLA class II antigens and idiopathic dilated cardiomyopathy (DCM), suggesting that genetically regulated immune response factors may be involved in the pathogenesis of this disease. In this study, families with DCM were used to test the hypothesis that a heritable gene defect in the HLA region is the primary genetic determinant for a subset of cases. Twelve families with DCM were identified. By formal segregation analysis, the inheritance of the disease was most consistent with an autosomal dominant gene defect with incomplete penetrance. Genotyping was performed with five highly polymorphic linked dinucleotide repeat markers that span the HLA locus. Linkage analysis was used to determine whether or not these genetic markers cosegregated with the disease phenotype. Genetic linkage between the disease phenotype and a 21 cM region spanning the HLA was excluded (lod score < or = -2) in at least 60% of our families. These results indicate that a gene defect in the HLA locus region is not the primary genetic determinant of DCM in a series of familial cases. However, our data do not exclude the possibility that HLA regulated immune response factors may have a modifying effect on disease penetrance and expression.

Possible involvement of the HLA-DQB1 gene in susceptibility and resistance to human dilated cardiomyopathy

There is evidence that autoimmunity plays a role in the pathogenesis of dilated cardiomyopathy and that susceptibility to the disease is related to products of human leukocyte antigens (HLA) class II genes. We compared the distribution of HLA-DQA1 and -DQB1 alleles and haplotypes in 44 normal controls and 34 patients with idiopathic dilated cardiomyopathy patients. The distribution of two DQA1-DQB1 haplotypes (*0102-*0604 and *0102-*0501) were more frequent in the patients. Histidine at position 30 of the HLA-DQB1 gene was associated with disease (62% of patients compared to 36% of controls), whereas homozygosity for leucine at position 26 was more frequent in controls (36% vs 18% of patients). There was no correlation between HLA-DQA1-DQB1 haplotypes and the presence of anti-beta-receptor antibodies. These results suggest that the HLA-DQB1 gene is involved in the pathogenesis of human dilated cardiomyopathy.

Familial dilated cardiomyopathy

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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.

A gene defect that causes conduction system disease and dilated cardiomyopathy maps to chromosome 1p1-1q1

Longitudinal evaluation of a seven generation kindred with an inherited conduction system defect and dilated cardiomyopathy demonstrated autosomal dominant transmission of a progressive disorder that both perturbs atrioventricular conduction and depresses cardiac contractility. To elucidate the molecular genetic basis for this disorder, a genome-wide linkage analysis was performed. Polymorphic loci near the centromere of chromosome 1 demonstrated linkage to the disease locus (maximum multipoint lod score = 13.2 in the interval between D1S305 and D1S176). Based on the disease phenotype and map location we speculate that gap junction protein connexin 40 is a candidate for mutations that result in conduction system disease and dilated cardiomyopathy.

Anti-beta-receptor antibodies in familial cardiomyopathy: correlation with HLA-DR and HLA-DQ gene polymorphisms

The presence of beta-receptor autoantibodies and their relationship to restriction fragment length polymorphisms of the human leukocyte antigen (HLA) class II genes were studied in 42 affected and unaffected members of a family with a heritable disorder of the conduction system and cardiac muscle. Antibodies were detected in 34% of all members (59% of affected and 22% of unaffected; p < 0.01). Significant differences between affected and unaffected individuals and between anti-beta-receptor antibody positive and negative individuals were noted in the prevalence of polymorphisms obtained with Taq I for the HLA-DR beta and HLA-DQ alpha genes. In affected individuals, there was a strong positive correlation between these polymorphisms and the presence of anti-beta-receptor antibodies. These results suggest that autoimmune mechanisms under the control of the class II genes play an important role in the pathogenesis of familial cardiomyopathy.

Circulating heart autoantibodies in familial as compared with nonfamilial idiopathic dilated cardiomyopathy

BACKGROUND

Idiopathic dilated cardiomyopathy (DCM) is a serious heart disease characterized by enlargement of one or both ventricles and ventricular dysfunction. Although most patients have sporadic disease, 20% have been found to have familial DCM when relatives are investigated by echocardiography. No other factors have been identified to date that consistently distinguish familial from nonfamilial DCM. Although some patients have a family history of DCM, a "negative" family history does not exclude familial DCM because affected family members may be presymptomatic or undiagnosed. Because some patients have life-threatening complications at the time of initial assessment of DCM, identifying a serum marker predictive of familial disease would help determine which families would most likely benefit from echocardiographic investigation.

OBJECTIVE

In this study, our objective was to determine whether antiheart autoantibodies could be used to distinguish familial from nonfamilial idiopathic DCM.

METHODS

We analyzed serum specimens for antiheart antibodies from 19 patients categorized as having familial DCM and 15 classified as having nonfamilial DCM on the basis of echocardiographic investigation of first-degree relatives. The mean duration of disease in these 34 patients was 50 months at the time the serum specimens were obtained.

RESULTS

Titers of antibodies against the adenine nucleotide translocator, branched-chain keto acid dehydrogenase, and cardiac myosin did not distinguish between familial and nonfamilial cases of DCM.

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.