Characterisation of genomic RNA of Coxsackievirus B3 in murine myocarditis: reliability of direct sequencing of reverse transcription-nested polymerase chain reaction products

Coxsackievirus B detection in cases of myocarditis, myopericarditis, pericarditis and dilated cardiomyopathy in hospitalized patients

Coxsackieviruses B (CV-B) are known as the most common viral cause of human heart infections. The aim of the present study was to assess the potential role of CV-B in the etiology of infectious heart disease in hospitalized patients. The present study is based on blood, pericardial fluid and heart biopsies from 102 patients and 100 control subjects. All of the samples were examined for the detection of specific enteroviral genome using the reverse transcription polymerase chain reaction (RT-PCR) and sequence analysis. Immunohistochemical investigations for the detection of the enteroviral capsid protein, VP1, from the biopsies were performed. The samples were cultured on confluent KB monolayer cell line for possible virus isolation. The epidemiological data were also collected. CV-B was detected in 28 of the 102 patients. The sequence analysis demonstrated that 27 strains were identical to CV-B3 and only one strain was identical to CV-B1. Furthermore, VP1 in the heart biopsies was detected in enterovirus-positive cases, as revealed by RT-PCR. Pericarditis infection was more frequent than myocarditis (P<0.05) or myopericarditis (P=0.05). The epidemiological data demonstrate that CV-B heart infections occur mainly during autumn and winter, and young male adults are more susceptible than adolescents or adults (P<0.5). The present findings demonstrate a higher prevalence of viral heart infections, suggesting that CV-B may significantly contribute to heart infections.

Enterovirus related metabolic myopathy: a postviral fatigue syndrome

OBJECTIVE

To detect and characterise enterovirus RNA in skeletal muscle from patients with chronic fatigue syndrome (CFS) and to compare efficiency of muscle energy metabolism in enterovirus positive and negative CFS patients.

METHODS

Quadriceps muscle biopsy samples from 48 patients with CFS were processed to detect enterovirus RNA by two stage, reverse transcription, nested polymerase chain reaction (RT-NPCR), using enterovirus group specific primer sets. Direct nucleotide sequencing of PCR products was used to characterise the enterovirus. Controls were 29 subjects with normal muscles. On the day of biopsy, each CFS patient undertook a subanaerobic threshold exercise test (SATET). Venous plasma lactate was measured immediately before and after exercise, and 30 minutes after testing. An abnormal lactate response to exercise (SATET+) was defined as an exercise test in which plasma lactate exceeded the upper 99% confidence limits for normal sedentary controls at two or more time points.

RESULTS

Muscle biopsy samples from 20.8% of the CFS patients were positive for enterovirus sequences by RT-NPCR, while all the 29 control samples were negative; 58.3% of the CFS patients had a SATET+ response. Nine of the 10 enterovirus positive cases were among the 28 SATET+ patients (32.1%), compared with only one (5%) of the 20 SATET- patients. PCR products were most closely related to coxsackie B virus.

CONCLUSIONS

There is an association between abnormal lactate response to exercise, reflecting impaired muscle energy metabolism, and the presence of enterovirus sequences in muscle in a proportion of CFS patients.

Myocarditis

Myocarditis and its sequela, dilated cardiomyopathy (DCM), cause substantial morbidity and mortality, especially in children and young adults. Physicians should include myocarditis in the differential diagnosis of all patients who have new symptoms of heart failure, arrhythmia, or chest pain syndromes of unclear cause, and should strongly consider performing endomyocardial biopsy (EMB) to establish the diagnosis. It may be necessary to perform multiple or serial biopsies to increase sensitivity. Patients with myocarditis and symptomatic heart failure, chest pain, or arrhythmias need hospitalization for evaluation and treatment. Patients with symptomatic left ventricular dysfunction should be treated with conventional heart failure therapy, including angiotensin-converting enzyme (ACE) inhibitors, digitalis, diuretics, and beta-blockers. Patients with arrhythmias or syncope may require electrophysiologic evaluation. In addition to conventional therapy, physicians should consider a course of immunosuppressive therapy in selected patients. The clinical course, response to therapy, and left ventricular function need close monitoring. Patients with myocarditis and rapidly progressive heart failure or cardiogenic shock should be referred early to an advanced heart failure center for implantation of a ventricular assist device and consideration for cardiac transplantation.

Myocarditis

Myocarditis and its sequela, dilated cardiomyopathy (DCM), cause substantial morbidity and mortality, especially in children and young adults. Physicians should include myocarditis in the differential diagnosis of all patients who have new symptoms of heart failure, arrhythmia, or chest pain syndromes of unclear cause, and should strongly consider performing endomyocardial biopsy (EMB) to establish the diagnosis. It may be necessary to perform multiple or serial biopsies to increase sensitivity. Patients with myocarditis and symptomatic heart failure, chest pain, or arrhythmias need hospitalization for evaluation and treatment. Patients with symptomatic left ventricular dysfunction should be treated with conventional heart failure therapy, including angiotensin-converting enzyme (ACE) inhibitors, digitalis, diuretics, and beta-blockers. Patients with arrhythmias or syncope may require electrophysiologic evaluation. In addition to conventional therapy, physicians should consider a course of immunosuppressive therapy in selected patients. The clinical course, response to therapy, and left ventricular function need close monitoring. Patients with myocarditis and rapidly progressive heart failure or cardiogenic shock should be referred early to an advanced heart failure center for implantation of a ventricular assist device and consideration for cardiac transplantation.

Characterization of enterovirus isolates from patients with heart muscle disease in a selenium-deficient area of China

An association of enterovirus infection with endemic cardiomyopathy (Keshan disease [KD]) and outbreaks of myocarditis in selenium-deficient rural areas of southwestern China has been established. Enteroviruses have been isolated from patients with KD or during outbreaks of myocarditis in last two decades. Six of these isolates grew readily in cell lines (Vero or HEp-2) and were investigated by a novel molecular typing method apart from serotyping and pathogenicity. A neutralization assay identified two isolates from KD as coxsackievirus serotype B2 (CVB2) and two isolates from myocarditis as coxsackievirus serotype B6 (CVB6) but failed to type the remaining two isolates, also from myocarditis. Direct nucleotide sequencing of reverse transcription-PCR products amplified from the 5' nontranslated region (5'NTR) of these viruses confirmed that they belong to a phylogenetic cluster consisting of coxsackie B-like viruses, including some echovirus serotypes. Sequence analysis of the coding region for viral capsid protein VP1 showed that two isolates serotyped as CVB2 have the highest amino acid sequence homology with CVB2 and that the remaining four isolates, two CVB6 and the two unknown serotypes, are most closely related to the sequence of CVB6. Sequences among these isolates varied from 82.3 to 99% in the 5'NTR and from 69 to 99% in VP1, indicating no cross contamination. The pathogenicity of these viruses in adult and suckling mice was assessed. None caused pathologic changes in the hearts of adult MF-1 or SWR mice, although pancreatitis was evident. However, the four CVB6-like viruses caused death in suckling mice, similar to a virulent coxsackievirus group B3 laboratory strain. In conclusion, the sequence data confirm that coxsackievirus group B serotypes are predominant in the region in which KD is endemic and may be the etiological agents in outbreaks of myocarditis. VP1 genotyping of enteroviruses is accurate and reliable. Animal experiments indicate that isolates may differ in pathogenicity.

High prevalence of enteroviral genomic sequences in myocardium from cases of endemic cardiomyopathy (Keshan disease) in China

OBJECTIVE

To verify the aetiological involvement of enterovirus and identify the viral genomic sequences in Keshan disease.

DESIGN

Formalin fixed, paraffin embedded myocardial necropsy tissue samples were collected in Keshan disease endemic regions. Fourteen cases with a histologically confirmed diagnosis of subacute or chronic Keshan disease were studied. Control tissue included 10 samples of myocardium from cases of cerebral trauma and one from accidental acid intoxication. One sample from a case of enteroviral myocarditis was used as a positive control. The presence of viral genomic RNA was investigated using an established reverse transcription nested polymerase chain reaction (PCR) coupled with direct nucleotide sequencing. Further investigations of PCR positive samples included in situ antigen detection or hybridisation to confirm positive results.

RESULTS

Nine of 14 myocardial samples from Keshan disease cases and the positive control were positive for the enteroviral RNA. All the controls were negative. Six of the PCR positive samples were investigated further by in situ enteroviral antigen or RNA detection and all were positive. DNA sequencing of six representative PCR products confirmed that they were homologous to the 5' non-translated region of enteroviral genomic RNA. Five had highest homology to coxsackievirus B genotypes and one was identical to poliovirus type 3.

CONCLUSIONS

These results support an aetiological role for enteroviral infection in Keshan disease. Nucleotide sequence data suggest that coxsackievirus B or coxsackie B like viruses are often involved in Keshan disease.