Enteroviral RNA and virus-like particles in the skeletal muscle of patients with idiopathic dilated cardiomyopathy

Major Persistent 5' Terminally Deleted Coxsackievirus B3 Populations in Human Endomyocardial Tissues

We performed deep sequencing analysis of the enterovirus 5′ noncoding region in cardiac biopsies from a patient with dilated cardiomyopathy. Results displayed a mix of deleted and full-length coxsackievirus B3, characterized by a low viral RNA load (8.10² copies/μg of nucleic acids) and a low viral RNA positive-sense to RNA negative-sense ratio of 4.8.

Diagnosis of myocarditis: Current state and future perspectives

Myocarditis, i.e. inflammation of the myocardium, is one of the leading causes of sudden cardiac death (SCD) and dilated cardiomyopathy (DCM) in young adults, and is an important cause of symptoms such as chest pain, dyspnea and palpitations. The pathophysiological process of disease progression leading to DCM involves an ongoing inflammation as a result of a viral-induced auto-immune response or a persisting viral infection. It is therefore crucial to detect the disease early in its course and prevent persisting inflammation that may lead to DCM and end-stage heart failure. Because of the highly variable clinical presentation, ranging from mild symptoms to severe heart failure, and the limited available diagnostic tools, the evaluation of patients with suspected myocarditis represents an important clinical dilemma in cardiology. New approaches for the diagnosis of myocarditis are needed in order to improve recognition, to help unravel its pathophysiology, and to develop new therapeutic strategies to treat the disease. In this review, we give a comprehensive overview of the current diagnostic strategies for patients with suspected myocarditis, and demonstrate several new techniques that may help to improve the diagnostic work-up.

Human enterovirus in the gastrocnemius of patients with peripheral arterial disease

Background

Peripheral arterial disease (PAD) is characterized by myofiber degeneration and loss of function in muscles of the lower limbs. Human enterovirus (HEV) infection has been implicated in the pathogenesis of a number of muscle diseases. However, its association with PAD has not been studied. In this study, we tested the hypothesis that infectious HEV is present in skeletal muscle of patients with PAD and is associated with severity of disease.

Methods and Results

Gastrocnemius biopsies from 37 patients with PAD and 14 controls were examined for the presence of HEV RNA, viral capsid protein, viral RNA copy number, and viral infectivity. HEV RNA was detected in 54% of the biopsies from patients with PAD but was not detected in muscle biopsies from control patients. This difference in prevalence among PAD and control patients was significant at P<0.001. Viral RNA copy numbers were increased significantly at the later stages of disease; Fontaine Stage IV (10^5.50 copies/mg muscle wet weight, at P<0.005) and Stage III (10^4.87 copies/mg, at P<0.010) compared to Stage II (10^2.50 copies/mg). Viral replication was confirmed by the presence of the negative‐strand of viral RNA in all specimens positive for HEV RNA. Cultures of HeLa and human skeletal muscle cells treated with muscle homogenates showed HEV replication and the presence of HEV capsid protein.

Conclusion

Our data identified infectious HEV in the gastrocnemius of PAD patients but not in controls. Viral copy number and prevalence of infection were higher in the later stages of disease. Our data point to the need for further studies to determine the contribution of HEV infection to the pathophysiology of PAD.

Persistent infection of human intestinal Caco-2 cell line by Coxsackieviruses B

Coxsackieviruses B (CV-B, Picornaviridae family, genus Enterovirus) are characterized by their ability to cause cytopathic effects in tissue culture. These viruses are considered highly cytolytic, but can establish persistence/latency in susceptible cells, indicating that a regulatory mechanism may exist to shut off viral protein synthesis and replication under certain situations. The persistence of coxsackieviral B RNA is of great interest because of its implication in the pathogenesis of several chronic human diseases. However, a few studies have dealt with the persistence of these viruses at the intestinal level. The aim of this study is to test the capacity of the six CV-B serotypes to establish persistent infection in human intestinal Caco-2 cell line. Ten CV-B isolates, including CV-B3 prototype strain (Nancy) and a recombinant isolate (B3-B4), were tested. Six CV-B isolates were found to establish persistent infections in Caco-2 cell line. Persistent replication was proved by the detection of viral RNA from cell cultures, VP1 capsid protein detection by immunofluorescence (IF) staining, and the release of infectious particles up to two months and a half after infection without any obvious cytolysis. In addition, our results suggest that the establishment of a persistent infection is serotype-independent.

Impairment of myocardial and skeletal mitochondria in mice with viral myocarditis and their correlation

In order to investigate the impairment of mitochondrial membrane phospholipid localization and DNA(3867) (mtDNA(3867)) deletion and the correlation between cardiac and skeletal muscle cells in mice with viral myocarditis, 50 BALB/c mice were divided into two groups randomly. In experimental group (n=40), the mice were intraperitoneally injected with 0.1 mL Eagle liquid with CVB3(TCID50=10(8)), while in the control group (n=10), the mice were subjected to equal volume of Eagle liquid. The impairment of mitochondrial membrane phospholipid localization and mtDNA(3867) deletion rate of cardiac and skeletal muscle were detected separately at day 3, 11 and 24 after injection. The correlation of mitochondrial membrane phospholipid localization and mtDNA(3867) deletion rate between cardiac and skeletal muscle cells cells was analyzed using Spearman method. At the day 3 after injection, in both cardiac and skeletal muscle cells, mtDNA(3867) deletion rate was significantly higher in experimental group than in control group (P<0.05), but the localization of mitochondrial membrane phospholipid showed no difference between two groups (P>0.05). At day 11 after injection, the mtDNA(3867) deletion rate of both cells in experimental group was increased to the peak level (P<0.05), and the impairment of mitochondrial membrane phospholipid localization of both cells also increased markedly in experimental group as compared with control group (P>0.05). At the day 24 after injection, the impairment of mitochondrial membrane phospholipid localization and mtDNA(3867) deletion of both cells showed a recovery tendency, but still severer than those at the day 3 after injection (P<0.05). The impairment of mitochondrial membrane phospholipid localization and mtDNA(3867) deletion were consistent and synchronistic between cardiac and skeletal muscle cells, and showed good correlations (P<0.05). The impairment of mitochondria plays an important role in the pathogenesis of viral myocarditis, and the skeletal muscle cells might act as a peripheral "window" to reflect the mitochondrial damage of cardiac myocytes.

Expression, purification and characterization of enterovirus-71 virus-like particles

AIM: Enterovirus 71 (EV71) has been implicated as the etiological agent responsible for the recent outbreaks of hand, foot and mouth disease associated with severe neurological diseases in the Asia-Pacific region.

METHODS: The assembly process was hypothesized to occur via an orchestrated proteolytic processing of the P1 precursor by the viral protease 3CD. To test this hypothesis, we constructed 3 recombinant baculoviruses: Bac-P1 expressing P1; Bac-3CD expressing 3CD; and Bac-P1-3CD co-expressing P1 and 3CD.

RESULTS: Both single infection by Bac-P1-3CD and co-infection by Bac-P1 and Bac-3CD resulted in correct cleavage of P1 to yield individual proteins VP0, VP1 and VP3, while the former approach yielded higher VLP production. In the cells, the structural proteins self-assembled into clusters of virus-like particles (VLP) resembling the authentic EV71 particle aggregates. After ultracentrifugation purification, the dispersed VLPs were indistinguishable from the authentic virus in size, appearance, composition and surface epitopes, as determined by SDS-PAGE, Western blot, transmission electron microscopy and immunogold labeling.

CONCLUSION: Our data, for the first time, suggest that in insect cells EV71 structural proteins adopt a processing and assembly pathway similar to poliovirus assembly. The preservation of particle morphology and composition suggest that the VLP may be a valuable vaccine candidate to prevent EV71 epidemics.

Association between enterovirus endomyocardial infection and late severe cardiac events in some adult patients receiving heart transplants

Enteroviruses and other cardiotropic viruses have been associated with the development of late severe adverse cardiac events in infants receiving heart transplants. However, the source and the chronology of cardiac allograft infection by an enterovirus in patients receiving heart transplants remain unknown. Using RT-PCR and immunohistochemistry assays, endomyocardial tissue samples of 30 adult patients were tested to detect the presence of specific enterovirus 5' non-coding (5'NC) sequences and of VP1 capsid protein, and this at the time of cardiac transplantation and at the 12-month biopsy for graft rejection control. Moreover, the endomyocardial detection of genomic sequences of enteroviruses, Epstein-Barr virus, herpes simplex virus, cytomegalovirus (CMV), varicella-zoster virus, adenoviruses, and parvovirus B19 was carried out by RT-PCR and polymerase chain reaction (PCR) assays at the time of late severe cardiac events. Enterovirus RNA and VP1 antigen were both detected in 4 (13%) of 30 patients at the time of the 12-month biopsy for graft rejection control, whereas no enterovirus component was detected in the explanted and implanted heart tissues taken from these 4 patients at the time of transplantation. At the time when severe cardiac events were developed, within 3 months after the positive enterovirus cardiac detection, these four patients demonstrated the presence of endomyocardial enterovirus RNA sequences whereas they were tested negative for the endomyocardial detection of genomic sequences from DNA viruses (except for CMV in two cases), and for a significant level of pp65 CMV antigenemia. Taken together, these findings indicate that enteroviruses could be acquired as a new endomyocardial infection within 12 months after transplantation in adults receiving heart transplants, and suggest that this infection might be an etiological cause for unexplained late severe adverse cardiac events in the heart-transplantated adults.

Detection of enterovirus in human skeletal muscle from patients with chronic inflammatory muscle disease or fibromyalgia and healthy subjects

Enterovirus RNA has been found previously in specimens of muscle biopsy from patients with idiopathic dilated cardiomyopathy, chronic inflammatory muscle diseases, and fibromyalgia or chronic fatigue syndrome (fibromyalgia/chronic fatigue syndrome). These results suggest that skeletal muscle may host enteroviral persistent infection. To test this hypothesis, we investigated by reverse transcription-polymerase chain reaction (RT-PCR) assay the presence of enterovirus in skeletal muscle of patients with chronic inflammatory muscle diseases or fibromyalgia/chronic fatigue syndrome, and also of healthy subjects. Three of 15 (20%) patients with chronic inflammatory muscle diseases, 4 of 30 (13%) patients with fibromyalgia/chronic fatigue syndrome, and none of 29 healthy subjects was found positive. The presence of VP-1 enteroviral capsid protein was assessed by an immunostaining technique using the 5-D8/1 monoclonal antibody; no biopsy muscle from any patient or healthy subject was found positive. The presence of viral RNA in some muscle biopsies from patients exhibiting muscle disease, together with the absence of VP-1 protein, is in favor of a persistent infection involving defective viral replication.

Prevalence and characteristics of dystrophin defects in adult male patients with dilated cardiomyopathy

OBJECTIVES

To assess the prevalence of dystrophin defects in dilated cardiomyopathy (DCM) in male patients and to formulate investigation strategies for their identification.

BACKGROUND

Dystrophin defects presenting with predominant or exclusive cardiac involvement may be clinically indistinguishable from "idiopathic" DCM. Diagnosis may be missed, unless specifically investigated.

METHODS

Clinical and biochemical evaluation, right ventricular endomyocardial biopsy (EMB), light and electron microscopic and immunohistochemical studies of biopsy samples, six multiplex and two single polymerase chain reactions for 38 exons and automated sequencing of exon 9 and muscle promoter-exon 1 were undertaken in 201 consecutive male patients presenting with DCM, with (n = 14) and without (n = 187) increased serum creatine phosphokinase (sCPK).

RESULTS

Dystrophin defects were identified in 13 of the 201 patients (6.5%, age 16-50). Family history was positive in four patients. Serum CPK levels were increased in 11 of 13 patients. Light microscopy examination of EMB was uninformative; ultrastructural study showed multiple membrane defects. Dystrophin immunostain was abnormal. Eight patients, all older than 20, had deletions affecting midrod domain, normal or mildly increased CPK and better outcome than the five remaining cases all younger than 20, with more than five-fold increase of sCPK. Two of these latter had proximal and rod-domain deletions. Sisters of two patients were diagnosed as noncarriers with microsatellite analysis.

CONCLUSIONS

Although the overall prevalence of dystrophin defects in our consecutive DCM male series is low (6.5%), immunohistochemical and molecular studies are essential to identify protein and gene defects; screening studies are justified to define prevalence, clinical profile and genotype-phenotype correlation.

Molecular mechanisms of coxsackievirus persistence in chronic inflammatory myopathy: viral RNA persists through formation of a double-stranded complex without associated genomic mutations or evolution

Enterovirus infection and persistence have been implicated in the pathogenesis of certain chronic muscle diseases. In vitro studies suggest that persistent enteroviruses mutate, evolving into forms that are less lytic and display altered tropism, but it is less clear whether these mechanisms operate in vivo. In this study, persistent coxsackievirus RNA from the muscle of mice afflicted with chronic inflammatory myopathy (CIM) was characterized and compared with RNA from a virus that had established a persistent infection of G8 mouse myoblasts for 30 passages in vitro. Competitive strand-specific reverse transcription-PCR and susceptibility to RNase I treatment revealed that plus- and minus-strand viral RNAs were present at nearly equivalent levels in muscle and that they persisted in a double-stranded conformation. All regions of the viral genome persisted and were amplified as a series of seven overlapping fragments. Restriction endonuclease fingerprinting coupled with sequencing indicated that there was no evolution of the viral genome associated with its persistence in muscle. This contrasted with the productive persistent infection that was established in myoblast cultures, where plus-strand RNA predominated and persistent virus developed distinct mutations. In vitro persistence proceeded by a carrier culture mechanism and was completely dependent on production of infectious virus, since persistent viral RNA was not detected in cultures subjected to antibody-mediated curing. These experiments demonstrate that persistence of coxsackievirus RNA in muscle is not facilitated by distinct genetic changes in the virus that give rise to replication-defective forms but occurs primarily through production of stable double-stranded RNA that is produced as the acute viral infection resolves. The data suggest a mechanism for coxsackievirus persistence in myofibers and perhaps other nondividing cells whereby cells that survive infection could harbor persistent viral RNA for extended times without producing detectable levels of infectious virus.