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.     

Mutational analysis of the cardiac actin gene in familial and sporadic dilated cardiomyopathy.

Dilated cardiomyopathy (DCM) results in part from genetic disorders. Recently, missense mutations of the cardiac actin gene have been reported to cause DCM. We studied 136 Japanese DCM cases to elucidate how frequently the gene mutations are involved in its pathogenesis. Genomic DNA samples were obtained from 136 DCM cases (107 males, 29 females), containing 30 familial DCM (5 confirmed and 25 suspected). All six exons of the cardiac actin gene were analyzed by polymerase chain reaction, single-strand conformation polymorphism, and sequencing. We detected no mutations of the disease causation previously reported (G867A or A1014G) but two silent mutations (G979C and C1018T) in exon 6 and one point mutation (T1080A) in the 3'-untranslated region. As a result of screening 128 healthy subjects, these novel silent mutations were found to be mere genetic polymorphisms, not responsible for the disease. Although some genetic polymorphisms exist in the cardiac actin gene, mutations of the gene are rarely responsible for DCM, at least in the Japanese patients.     

Mutational analysis of the cardiac actin gene in familial and sporadic dilated cardiomyopathy

Dilated cardiomyopathy (DCM) results in part from genetic disorders. Recently, missense mutations of the cardiac actin gene have been reported to cause DCM. We studied 136 Japanese DCM cases to elucidate how frequently the gene mutations are involved in its pathogenesis. Genomic DNA samples were obtained from 136 DCM cases (107 males, 29 females), containing 30 familial DCM (5 confirmed and 25 suspected). All six exons of the cardiac actin gene were analyzed by polymerase chain reaction, single-strand conformation polymorphism, and sequencing. We detected no mutations of the disease causation previously reported (G867A or A1014G) but two silent mutations (G979C and C1018T) in exon 6 and one point mutation (T1080A) in the 3′-untranslated region. As a result of screening 128 healthy subjects, these novel silent mutations were found to be mere genetic polymorphisms, not responsible for the disease. Although some genetic polymorphisms exist in the cardiac actin gene, mutations of the gene are rarely responsible for DCM, at least in the Japanese patients. Am. J. Med. Genet. 86:325–327, 1999. © 1999 Wiley-Liss, Inc.     

Anti-heart autoantibodies in familial dilated cardiomyopathy

Familial aggregation is a feature of myocarditis and dilated cardiomyopathy (DCM). Myocarditis, a clinically polymorphic inflammatory disease of the myocardium, is diagnosed by endomyocardial biopsy (EMB) and may lead to DCM. Mutations in several genes encoding myocyte structural proteins are known monogenic DCM causes, but because of high etiologic and genetic heterogeneity, the gene defects identified so far account for a minority of cases. In the last decade, it has been discovered that autoimmunity plays a pivotal role in myocarditis and DCM that are thought to represent different stages of an organ-specific autoimmune disease in genetically predisposed individuals. None of the available genetic studies in familial DCM has taken into account the autoimmune phenotype markers in the characterization of index patients and relatives, thus it is not known whether or not the described gene defects are involved in the autoimmune form of the disease. In animal models autoimmune myocarditis/DCM can be induced by viral infection, immunization with heart-specific autoantigens, or develop spontaneously in genetically predisposed strains. It may be cell or antibody-mediated; susceptibility is based upon multiple MHC and non-MHC genes. In patients, the diagnosis of autoimmune myocarditis/DCM requires exclusion of viral genome on EMB and detection of serum heart-reactive autoantibodies. They are found in index patients and relatives from about 60% of both familial and non-familial pedigrees and predict DCM development among healthy relatives. Some antibodies have functional effects on cardiac myocytes in vitro, in animal models and possibly in a DCM subset without inflammation, responsive to extracorporeal immunoadsorption. Cardiac-specific autoantibodies, which are shown to be disease-specific for myocarditis/DCM, can be used as biomarkers for identifying patients in whom, in the absence of active infection of the myocardium, immunosuppression and/or immunomodulation may be beneficial and their relatives at risk. Future studies should clarify genetic basis of human autoimmune myocarditis/DCM as well as genotype/immune phenotype correlations.     

Mutations in the dystrophin gene are associated with sporadic dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is the major indication for heart transplantation. Approximately 30% of all DCM is thought to be inherited, while 70% is sporadic. Mutations in the dystrophin gene have been associated with the uncommon X-linked form of DCM. We hypothesized that missense mutations and other less severe mutations of the dystrophin gene might predispose to the common form of sporadic DCM. To test this hypothesis, 22kb of genomic dystrophin DNA was scanned with DOVAM-S in each of the 22 patients with sporadic DCM, including all 79 coding sequences and splice junctions, as well as six alternative exon 1 dystrophin isoforms (484kb, total). Three putative new mutations (IVS5+1 G>T, K18N, and F3228L) and seven polymorphisms were identified. The splice site mutation IVS5+1 is predicted to cause skipping of exon 5, which is within a region containing an actin binding site. The missense mutations occur at amino acids that display substantial evolutionary conservation. Screening of 236 control individuals failed to identify these three mutations. The three patients with putative mutations had CK-MM (creatine kinase, skeletal muscle) levels greater than 250 units while the 14 patients without mutations for which CK-MM were available had values ranging from 20 to 200. The first comprehensive mutation scanning of the exons and splice junctions of the dystrophin gene in patients with sporadic DCM presents the evidence that point mutations are associated with sporadic DCM without clinical evidence of skeletal myopathy. It may be prudent to measure CK-MM in all patients with dilated cardiomyopathy to identify candidates at high risk for dystrophin mutations.     

Spatiotemporal changes of coxsackievirus and adenovirus receptor in rat hearts during postnatal development and in cultured cardiomyocytes of neonatal rat

Coxsackievirus B is the most common cause of viral myocarditis and is particularly virulent in neonates and children. Adenovirus is also a leading cause of the disease. The determinant of tropism for both viruses is considered to be the expression of coxsackievirus and adenovirus receptor (CAR) in target organs. However, developmental change and physiological localization of CAR in the heart are unknown. We examined expression levels of CAR in rat hearts by quantitative real-time polymerase chain reaction and Western blot analysis and found that CAR decreased gradually during postnatal development, although CAR was detectable, even in adults. Immunohistochemistry revealed CAR on the whole surface of cardiomyocytes in immature rat hearts. In contrast, CAR was detected predominantly on intercalated disks in the adult heart and was accumulated especially at the contact point between the cultured cardiomyocytes, even though they were prepared from the neonatal rat heart. In conclusion, CAR was expressed abundantly on the whole surface of cardiomyocytes in immature rat hearts. Both the expression level and the localization of CAR are possible determinants of the susceptibility to viral myocarditis of neonates and children.     

Mutational analysis of the beta- and delta-sarcoglycan genes in a large number of patients with familial and sporadic dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is defined by ventricular dilatation associated with impaired contractile function. Approximately one-third of idiopathic dilated cardiomyopathy cases are due to inherited gene mutations. Mutations in the beta- and delta-sarcoglycan genes have been described in limb girdle muscular dystrophy and/or isolated DCM. In this study, the aim was to investigate the prevalence of these genes in isolated DCM. We screened these two genes for mutations in 99 unrelated patients with sporadic or familial DCM. The coding exon and intron-exon boundaries of each gene were amplified by polymerase chain reaction. Mutation analyses were performed by single-strand conformation polymorphism for the beta-sarcoglycan gene and by direct sequencing for the delta-sarcoglycan gene. New polymorphisms, as well as already described ones, were found in these two genes, but none appeared to be responsible for dilated cardiomyopathy. We, therefore, conclude that these genes are not responsible for idiopathic isolated dilated cardiomyopathy in our population. Furthermore, based on previously published and present data, we could estimate the prevalence of delta-sarcoglycan gene mutations to be less than 1% in idiopathic dilated cardiomyopathy, demonstrating that this gene is only marginally implicated in the disease.     

Clinical implications of anti-heart autoantibodies in myocarditis and dilated cardiomyopathy

Dilated cardiomyopathy (DCM), a leading cause of heart failure and heart transplantation in younger adults, is characterized by dilatation and impaired contraction of the left or both ventricles; it may be idiopathic, familial/genetic (20-30%), viral, and/or immune. On endomyocardial biopsy there is chronic inflammation in 30-40% of cases. Mutations in genes encoding myocyte structural proteins, cardiotoxic noxae and infectious agents are known causes; due to high aetiologic and genetic heterogeneity, the gene defects identified so far account for a tiny proportion of the familial cases. In at least two thirds of patients, DCM remains idiopathic. Myocarditis may be idiopathic, infectious or autoimmune and may heal or lead to DCM. Circulating heart-reactive autoantibodies are found in myocarditis/DCM patients and symptom-free relatives at higher frequency than in normal or noninflammatory heart disease control groups. These autoantibodies are directed against multiple antigens, some of which are expressed only in the heart (organ-specific); some autoantibodies have functional effects on cardiac myocytes in vitro as well as in animal models. Depletion of nonantigen-specific antibodies by extracorporeal immunoadsorption is associated with improved ventricular function and reduced cardiac symptoms in some DCM patients, suggesting that autoantibodies may also have a functional role in humans. Immunosuppression seems beneficial in patients who are virus-negative and cardiac autoantibody positive. Prospective family studies have shown that cardiac-specific autoantibodies are present in at least 60% of both familial and non familial pedigrees and predict DCM development among asymptomatic relatives, years before clinical and echocardiographic evidence of disease. Animal models have shown that autoimmune myocarditis/DCM can be induced by virus as well as reproduced by immunization with a well-characterized autoantigen, cardiac myosin. Thus, in a substantial proportion of patients, myocarditis and DCM represent different stages of an organ-specific autoimmune disease, that represents the final common pathogenetic pathway of infectious and noninfectious myocardial injuries in genetically predisposed individuals.     

Clinical implications of anti-heart autoantibodies in myocarditis and dilated cardiomyopathy

Dilated cardiomyopathy (DCM), a leading cause of heart failure and heart transplantation in younger adults, is characterized by dilatation and impaired contraction of the left or both ventricles; it may be idiopathic, familial/genetic (20–30%), viral, and/or immune. On endomyocardial biopsy there is chronic inflammation in 30–40% of cases. Mutations in genes encoding myocyte structural proteins, cardiotoxic noxae and infectious agents are known causes; due to high aetiologic and genetic heterogeneity, the gene defects identified so far account for a tiny proportion of the familial cases. In at least two thirds of patients, DCM remains idiopathic. Myocarditis may be idiopathic, infectious or autoimmune and may heal or lead to DCM. Circulating heart-reactive autoantibodies are found in myocarditis/DCM patients and symptom-free relatives at higher frequency than in normal or noninflammatory heart disease control groups. These autoantibodies are directed against multiple antigens, some of which are expressed only in the heart (organ-specific); some autoantibodies have functional effects on cardiac myocytes in vitro as well as in animal models. Depletion of nonantigen-specific antibodies by extracorporeal immunoadsorption is associated with improved ventricular function and reduced cardiac symptoms in some DCM patients, suggesting that autoantibodies may also have a functional role in humans. Immunosuppression seems beneficial in patients who are virus-negative and cardiac autoantibody positive. Prospective family studies have shown that cardiac-specific autoantibodies are present in at least 60% of both familial and non familial pedigrees and predict DCM development among asymptomatic relatives, years before clinical and echocardiographic evidence of disease. Animal models have shown that autoimmune myocarditis/DCM can be induced by virus as well as reproduced by immunization with a well-characterized autoantigen, cardiac myosin. Thus, in a substantial proportion of patients, myocarditis and DCM represent different stages of an organ-specific autoimmune disease, that represents the final common pathogenetic pathway of infectious and noninfectious myocardial injuries in genetically predisposed individuals.     

Cardiac autoantibodies to myosin and other heart-specific autoantigens in myocarditis and dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is characterized by dilation and impaired contraction of the left ventricle or both; it is a relevant cause of heart failure and a common indication for heart transplantation. It may be idiopathic, familial/genetic, viral, autoimmune or immune-mediated, associated with a viral infection. Myocarditis is an inflammatory disease of the myocardium; it may be idiopathic, infectious or autoimmune and may heal or lead to DCM. Thus, in a patient subset, myocarditis and DCM are thought to represent the acute and chronic stages of an organ-specific autoimmune disease of the myocardium. In keeping with this hypothesis, 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, detection of organ- and disease-specific cardiac autoantibodies in the sera of affected patients and of symptom-free relatives. 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 immunization with cardiac but not skeletal myosin reproduces, in susceptible mouse strains, the human disease phenotype of myocarditis/DCM; in addition, alpha-myosin is entirely cardiac-specific. The organ-specific cardiac autoantibodies detected by immunofluorescence in symptom-free relatives were associated with echocardiographic features suggestive of early disease. Short-term follow-up is in keeping with this interpretation, although extended follow-up is necessary to define better the role of the antibody as predictor of disease susceptibility in healthy subjects at risk of myocarditis/DCM, such as first-degree relatives.     

Detection of enteroviral infection in myocardial tissues by polymerase chain reaction (PCR)

Objective: To determine if enteroviral infection is linked to myocarditis and dilated cardiomyopathy. Enteroviruses, especially coxsackieviruses, appear to be the most common agents of viral myocarditis.
Methods: We collected 53 endomyocardial biopsies and two autopsy specimens from 41 patients affected by myocarditis or dilated cardiomyopathy. The patients were diagnosed clinically, hemodynamically, virologically and histologically (Dallas classification). We tested for the presence of enteroviral sequences by PCR, using 5' non-coding (coxsackievirus B3, CB3, map position 450–474, 584–603) derived primers. Specificity was confirmed using the Southern blot. We used a fraction of CB3 acutely infected mouse myocardial tissue as a control.
Results: We detected enteroviral sequences in four patients with active myocarditis, borderline myocarditis or cardiomyopathy. The patient with active myocarditis had shown neutralizing antibodies in serologic analysis for coxsackievirus B3 and B5.
Conclusions: The data support a weak link of enteroviral infection to human myocarditis and dilated cardiomyopathy, at least when using a PCR assay on biopsies.     

Prevalence of the parvovirus B19 genome in endomyocardial biopsy specimens

Although enteroviruses have long been considered the most common cause of inflammatory heart muscle diseases, parvovirus B19 (PVB19) is emerging as a new and important candidate for myocarditis and dilated cardiomyopathy with inflammation (DCMi) and without inflammation (DCM). We investigated left ventricular endomyocardial biopsy specimens from 110 patients with suspected inflammatory heart disease for the presence of PVB19, Coxsackie virus (CVB), and adenovirus (Ad2) genome by polymerase chain reaction. Diagnosis of myocarditis (36 patients), DCM (18 patients), DCMi (13 patients), and perimyocarditis (12 patients) was made by immunohistochemical and histopathological investigation of endomyocardial biopsy specimens. A control group consisting of patients with arterial hypertension was also investigated. Prevalence of the PVB19 genome in endomyocardial biopsy specimens was highest in patients with DCMi (3 of 13) and patients with myocarditis (7 of 36); in patients with DCM and perimyocarditis, prevalence was 3 of 13 and 2 of 12, respectively. In patients with resolved myocarditis, no PVB19 DNA was detected; in patients with no inflammation and controls, prevalence was only 4% and 7%, respectively. CVB-RNA was detected in endomyocardial biopsy specimens from 3 of 37 patients with myocarditis; Ad2-DNA was found in 1 patient with DCM and 1 patient with perimyocarditis. These findings suggest an association of the PVB19 genome in endomyocardial biopsy specimens of adults with the development of DCM, DCMi, and chronic myocarditis more frequently than previously expected. PVB19 should therefore be recognized as a potential cardiotropic pathogen in patients of all ages.     

Treatment of coxsackievirus-B3-infected BALB/c mice with the soluble coxsackie adenovirus receptor CAR4/7 aggravates cardiac injury

Coxsackie adenovirus receptor (CAR) is involved in immunological processes, and its soluble isoforms have antiviral effects on coxsackievirus B3 (CVB3) infection in vitro. We explored in this study the impact of CAR4/7, a soluble CAR isoform, on CVB3-induced myocarditis in BALB/c mice. BALB/c mice were treated daily with recombinant CAR4/7, β-galactosidase (β-Gal; as control protein) or buffer for 9 days. Half of each group was infected with CVB3 on day 3, and all mice were killed on day 9. Myocardial CVB3 titer, histology, and serology were analyzed. Treatment with CAR4/7 led to a significant reduction of myocardial CVB3 titer, whereas the application of β-Gal had no detectable effect on the myocardial virus load. CAR4/7 application, however, resulted in increased myocardial inflammation and tissue damage in CVB3-infected hearts, whereas β-Gal caused a degree of cardiac inflammation and injury similar to that in buffer-treated CVB3-infected control animals. CAR4/7 and β-Gal treatment induced the production of antibodies against the respective antigens. CAR4/7-, but not β-Gal-specific, virus-negative sera reacted against myocardial tissue and cellular membranous CAR, and significantly inhibited CVB3 infection in vitro. Thus, CAR4/7 suppressed CVB3 infection in vivo, supporting the concept of receptor analog in antiviral therapy. However, CAR4/7 treatment also leads to an aggravation of myocardial inflammation and injury most likely secondary to an autoimmune process.     

病毒性心脏病小鼠心脏胶原代谢的动态变化

目的：探讨急、慢性病毒性心肌炎和扩张型心肌病小鼠心肌组织中胶原代谢的动态变化和特征。方法：以柯萨奇病毒B3感染BALB/c小鼠分别建立病毒性心脏病动物模型，同期均设正常对照。组织病理学方法和心脏超声确认动物模型后，以酶联免疫吸附法（ELISA）检测各组小鼠胶原前肽（PINP、PICP和PIIINP）的血清浓度；以免疫印迹法（Western blotting）检测间质胶原酶（MMP-1）及其组织抑制物（TIMP-1）在心肌组织中的表达；同时检测MMP-1活性变化结果：各期感染小鼠心脏均出现明显心肌纤维化，急性期为修复性心肌纤维化，胶原合成和降解均增强；慢性期反应性纤维化和修复性纤维化并存，胶原合成增多降解减少；心肌病理主要为反应性纤维化，胶原合成增多；MMP-1表达量和活性随病程进行性减少，TIMP-1的表达无变化，MMP-1/TIMP-1进行性降低。结论：病毒性心脏病不同时期胶原代谢有其各自的特点，对病程和预后的影响不同。     

Association of innate immune IFIH1 gene polymorphisms with dilated cardiomyopathy in a Chinese population

The interferon-induced helicase C domain-containing protein 1 (IFIH1) is a cytosolic RNA sensor belonging to the pattern-recognition receptor (PPR) family. Activation of PPRs on innate immune cells is widely believed to control the development of virus-induced autoimmunity in myocarditis and subsequent dilated cardiomyopathy (DCM). We conducted a pilot study to test whether single nucleotide polymorphisms (SNPs) in IFIH1 were associated with the risk and prognosis of DCM. The TaqMan SNP Genotyping Assay was used to genotype rs1990760 and rs3747517 in 351 DCM patients and 359 controls. The frequency of T allele and CT/TT genotypes at rs1990760 were significantly increased in DCM patients compared to control subjects (p?=?0.046 and p?=?0.027, respectively). The CC homozygosity was associated with worse prognosis expressed by the endpoint of cardiac death compared with allele T carriers of rs3747517 in both univariable (p?=?0.04) and multivariable survival analysis after adjusting for age, sex, left ventricular end-diastolic diameter and ejection fraction (p?=?0.01). The results revealed that rs1990760 was associated with susceptibility to DCM and rs3747517 played a role in the prognostic assessment of DCM, reflecting the distinct genetic contributions of innate IFIH1 polymorphisms in controlling the onset and outcome of DCM.     

Evaluation of coxsackievirus and adenovirus receptor expression in human benign and malignant thyroid lesions

Giaginis C, Zarros A, Alexandrou P, Klijanienko J, Delladetsima I, Theocharis S. Evaluation of coxsackievirus and adenovirus receptor expression in human benign and malignant thyroid lesions. APMIS 2010; 118: 210–21. Coxsackievirus and adenovirus receptor (CAR) expression on tumor cells is associated with sensitivity to adenoviral infection, being considered as a surrogate marker for monitoring and/or predicting adenovirus‐mediated gene therapy. The aim of this study was to evaluate the clinical significance of CAR expression in human benign and malignant thyroid lesions. CAR protein expression was assessed immunohistochemically on paraffin‐embedded thyroid tissues from 107 patients with benign and malignant lesions and was statistically analyzed in relation to histopathologic type; tumor size; lymph node metastasis; capsular, lymphatic and vessel invasion; as well as follicular cells’ proliferative capacity. CAR immunoreactivity was characterized as negative/weak in 53 (49.53%), moderate in 31 (28.97%) and strong in 23 (21.50%) of 107 thyroid cases. CAR immunoreactivity was significantly increased in malignant compared with that in benign thyroid lesions (p = 0.00002). Both malignant and benign thyroid lesions with enhanced follicular cells’ proliferative capacity showed significantly increased CAR immunoreactivity (p = 0.00027). In malignant thyroid lesions, enhanced CAR immunoreactivity was significantly associated with larger tumor size (p = 0.0067). The current data revealed that CAR immunoreactivity could be considered of diagnostic utility in thyroid neoplasia. Further research effort is warranted to delineate whether CAR could be considered clinically important for both diagnosis and future (gene) therapeutic applications in thyroid neoplasia.     

Detection of enterovirus capsid protein VP1 in myocardium from cases of myocarditis or dilated cardiomyopathy by immunohistochemistry: further evidence of enterovirus persistence in myocytes

The association of enteroviruses with myocardial disease has been investigated extensively by molecular biological techniques to detect viral RNA, but remains controversial. This retrospective study investigated the involvement of enterovirus in myocarditis or dilated cardiomyopathy (DCM) by detection of viral antigens in myocardial samples from a new patient series using an optimized immunohistochemical technique. Formalin-fixed, paraffin-embedded biopsy, autopsy or explanted myocardial tissue samples were obtained from 136 subjects. These comprised histologically proven cases of acute fatal myocarditis (n=10), DCM (n=89, including 10 patients with healing/borderline myocarditis) and a comparison group of samples from 37 unused donor hearts and cases with other conditions. A monoclonal antibody 5-D8/1 directed against a conserved, non-conformational epitope in capsid protein VP1 was employed for broad detection of different enterovirus serotypes. Investigations were performed blindly. Histological sections from 7 of 10 fatal myocarditis cases, 47 of 89 patients (52.8%) with DCM were positive for the viral capsid protein VP1 by immunohistochemical staining. Consecutive sections of positive samples were negative when the antibody was omitted or replaced with subclass- and concentration-matched normal mouse IgG. In contrast, only 3 of 37 samples (8.1%) in the comparison group were positive (Yates corrected ²=19.99, P<0.001: odds ratio =12.68). VP1 staining was distributed in individual or grouped myofibers and localized in the cytoplasm of myocytes. In some cases, VP1 was detected in only a few myofibers within an entire section. These results provide further evidence of enterovirus involvement in a high proportion of DCM cases and demonstrate that VP1 is present in disease stages from acute myocarditis, healing myocarditis to end-stage DCM requiring cardiac transplantation, indicating translation of viral protein during persistent enterovirus infection.     

Enteroviraf RNA in endomyocardial biopsy tissues of myocarditis and dilated cardiomyopathy

Enteroviruses are potential etiologic agents of myocarditis and dilated cardiomyopathy (DCM). A recently developed molecular approach has offered evidence of viral infection by detecting the virus genome. The nested reverse transcrip-tase polymerase chain reaction (nRT-PCR) was used to detect enteroviral RNA in endomyocardial biopsy tissues of myocarditis and DCM. The authors examined 44 tissues obtained from 36 patients with myocarditis, as well as from 10 patients with non-infectious cardiac diseases as controls.
Enteroviral RNA was detected in 12 of 36 patients with myocarditis. The second endomyocardial biopsy was carried out in five of the patients, in whom enteroviral RNA was detected at the first biopsy, at intervals from 3 weeks to 8 years after the first biopsy, and enteroviral RNA was found in four and had disappeared in one. In one of the four positive patients at the second biopsy, a third biopsy was carried out 5 months later (6 months after the first), and the RNA was detected. Active myocarditis became clinically and microscopically mild at the second and third biopsies. In one patient who developed DCM, enteroviral RNA was also detected at a second biopsy performed 8 years after the first. Enteroviral infection is a probable cause of myocarditis and enterovirus-infected myocarditis may progress to DCM.