Viral infection and the pathogenesis of dilated cardiomyopathy

Long-term follow-up studies of patients with suspected viral myocarditis reveal progression to dilated cardiomyopathy (DCM) in a significant number of cases. Thus, an underlying viral etiology has been hypothesized in the pathogenesis of ongoing heart disease that leads to DCM. Recent application of molecular biology in clinical diagnosis has strengthened this hypothesis. By use of probe hybridization and polymerase chain reaction, enteroviral RNA has been detected in the myocardium of patients at all stages of the disease process: myocarditis, chronic heart disease, and DCM. Experimental murine models of enterovirus-induced heart disease provide a framework for examining the pathogenic mechanisms. Viral cytotoxicity, immunological responses, viral RNA persistence, and spasm of the coronary microvasculature are all implicated in the ongoing disease process. Abnormal cardiac function and heart failure are attributed to the pathological changes that occur.

Molecular evolution of the major capsid protein VP1 of enterovirus 70

Nucleotide sequences of the genome RNA encoding capsid protein VP1 (918 nucleotides) of 18 enterovirus 70 (EV70) isolates collected from various parts of the world in 1971 to 1981 were determined, and nucleotide substitutions among them were studied. The genetic distances between isolates were calculated by the pairwise comparison of nucleotide difference. Regression analysis of the genetic distances against time of isolation of the strains showed that the synonymous substitution rate was very high at 21.53 x 10(-3) substitution per nucleotide per year, while the nonsynonymous rate was extremely low at 0.32 x 10(-3) substitution per nucleotide per year. The rate estimated by the average value of synonymous and nonsynonymous substitutions (W.-H. Li, C.-C. Wu, and C.-C. Luo, Mol. Biol. Evol. 2:150-174, 1985) was 5.00 x 10(-3) substitution per nucleotide per year. Taking the average value of synonymous and nonsynonymous substitutions as genetic distances between isolates, the phylogenetic tree was inferred by the unweighted pairwise grouping method of arithmetic average and by the neighbor-joining method. The tree indicated that the virus had evolved from one focal place, and the time of emergence was estimated to be August 1967 +/- 15 months, 2 years before first recognition of the pandemic of acute hemorrhagic conjunctivitis. By superimposing every nucleotide substitution on the branches of the phylogenetic tree, we analyzed nucleotide substitution patterns of EV70 genome RNA. In synonymous substitutions, the proportion of transitions, i.e., C<==>U and G<==>A, was found to be extremely frequent in comparison with that reported on other viruses or pseudogenes. In addition, parallel substitutions (independent substitutions at the same nucleotide position on different branches, i.e., different isolates, of the tree) were frequently found in both synonymous and nonsynonymous substitutions. These frequent parallel substitutions and the low nonsynonymous substitution rate despite the very high synonymous substitution rate described above imply a strong restriction on nonsynonymous substitution sites of VP1, probably due to the requirement for maintaining the rigid icosahedral conformation of the virus.

Studies on enterovirus in patients with chronic fatigue syndrome

A large study on 121 patients with the chronic fatigue syndrome (CFS) that examined muscle biopsy samples for enterovirus by means of polymerase chain reaction analysis was carried out. The results were compared with those obtained from 101 muscle biopsy specimens from patients with a variety of other neuromuscular disorders (OND), including neurogenic atrophies, dystrophies, and mitochondrial, metabolic, and endocrine myopathies. Thirty-two (26.4%) of the biopsy specimens from the group of patients with CFS were positive, compared with 20 (19.8%) from the group of patients with OND, a difference that was not significant. This finding is in contrast to those of our previous smaller study in which significantly more patients with CFS than control subjects (53% [32 of 60] vs. 15% [6 of 41]) had enterovirus RNA sequences in their muscle. It was concluded that it is unlikely that persistent enterovirus infection plays a pathogenetic role in CFS, although an effect in initiating the disease process cannot be excluded.

Detection of coxsackie B4 virus RNA in infected mouse kidneys by in situ hybridization

We describe a method for detecting virus-specific RNA sequences using a nonradioactive enzyme system, and analyze coxsackie B4 virus (cox.B4) RNA sequences in infected mouse kidney with pathological changes. Diffuse mesangial proliferation was observed transiently 24 h after inoculation of cox.B4 virus in glomeruli. OCT-treated thin sections of the same tissue were hybridized in situ using a digoxigenin-labeled oligonucleotide probe. The strongest signal was observed in the mesangial sample. These findings suggest that the transient proliferative mesangial changes were caused by direct injury following virus infection without immune complex.

Use of genomic probes to detect hepatitis A virus and enterovirus RNAs in wild shellfish and relationship of viral contamination to bacterial contamination

Genomic probes were used to investigate hepatitis A virus (HAV) and enterovirus RNAs in two types of shellfish from natural beds (Atlantic coast, France). After elution concentration, nucleic acid extracted by proteinase K and purified by phenol-chloroform and ethanol precipitation was assayed by dot blot hybridization. The probes used were a specific HAV probe corresponding to the 3' end (3D polymerase coding region) and an enterovirus probe corresponding to the 5' noncoding region. The method was first tested under experimental conditions by using virus-spiked shellfish before being applied under field conditions. Our results show that shellfish were highly contaminated: enterovirus and HAV RNAs were found in 63 and 67%, respectively, of samples examined with the riboprobes. On the same site, viral (HAV and enterovirus) RNAs were found in a larger fraction of cockles than mussels. Statistical tests of dependence showed no relationship between viral contamination and bacterial contamination (evaluated by fecal coliform counts).

Prevalence of newly isolated, cytopathic small round virus (Aichi strain) in Japan

Cytopathic small round virus (Aichi strain), isolated from a patient with oyster-associated gastroenteritis, showed no reaction in the polymerase chain reaction method for enteroviruses or in the enzyme-linked immunosorbent assay (ELISA) for the five serotypes of astroviruses. Our ELISA was sensitive in detecting the Aichi strain antigen in stool samples, but there was no reaction in this ELISA with any non-Aichi strains of enteric viruses, with such origins as enterovirus, rotavirus, Norwalk virus, calicivirus, or astrovirus. In the ELISA, 13 of 47 stool samples from adult patients in five of nine oyster-associated gastroenteritis outbreaks were positive, but only 1 of 397 pediatric stool samples in Aichi Prefecture was positive. The prevalence rate for Aichi strain antibody was found to be 7.2% for persons aged 7 months to 4 years. The prevalence rate for antibody to Aichi strain increased with age, to about 80% in persons 35 years old. On the basis of the results of the present study, it was hypothesized that Aichi strain could be a new type of small round virus that mainly produces diarrhea in patients in the 15- to 34-year-old age group, 50 to 76% of whom possess neutralizing antibody.

Diagnosis of enterovirus brain disease in hypogammaglobulinemic patients by polymerase chain reaction

CSF samples taken from three patients with primary hypogammaglobulinemia and chronic brain disease were positive for enterovirus RNA by use of a technique based on the polymerase chain reaction (PCR) to amplify viral genomic sequences. Repeated attempts to culture viruses from the CSF from these patients were unsuccessful, possibly because the patients were treated regularly with intravenous immunoglobulin, which may have contained enough specific antibody to partially neutralize the viruses. Our data suggest that enteroviruses are responsible for diverse CNS features in patients with primary hypogammaglobulinemia and that for these patients the diagnosis should be pursued using PCR technology.

Simple method of concentrating enteroviruses and hepatitis A virus from sewage and ocean water for rapid detection by reverse transcriptase-polymerase chain reaction

A rapid and simple method was developed to detect enteroviruses and hepatitis A virus (HAV) in sewage and ocean water. Sewage samples were concentrated by Centriprep-100 and Centricon-100 at 1,000 x g. Samples collected from estuary and near-shore surf zone ocean water in Southern California were concentrated by vortex flow filtration and microconcentration. Reverse transcriptase-polymerase chain reaction (RT-PCR), with enterovirus primers or HAV capsid-specific primers, was used to detect enteroviruses or HAV in all concentrated samples. A nonradioactive internal probe was used to confirm the amplified products. Results of seeding experiments indicated that at 4 degrees C, HAV was more persistent than poliovirus in seawater and both HAV and poliovirus persisted longer at 4 degrees C than at 25 degrees C. RT-PCR was at least 500-fold more sensitive than cell culture. Results were obtained within 5 h by RT-PCR, in contrast with the 5 days to 3 weeks required for cell culture.

Quantitation of enteroviral RNA by competitive polymerase chain reaction

The polymerase chain reaction (PCR) is a new diagnostic technique for the detection of enteroviral infection; however, it currently provides only qualitative results. The aim of this study was to adapt PCR for the accurate quantitation of enteroviral RNA in clinical specimens. For this purpose, we designed a standard RNA which was homologous to sequences at the 5' end of the coxsackie B3 enterovirus genome but contained a single-base-pair mutation which created a novel internal restriction site. Serial dilutions of this standard template RNA were mixed with a fixed concentration of coxsackie B3 enterovirus RNA. The viral and standard templates were reversed transcribed to cDNA and coamplified by PCR, and a comparison of the radioactive PCR products was made. Since the templates were both present in a single reaction tube and competed for the same primers, the ratio of products remained proportional throughout the amplification process. By this approach, a fourfold-difference in viral titer was clearly distinguishable. Moreover, we were able to accurately quantitate as few as 15 50% tissue culture infectious doses, which reflects common clinical viral titers. This study lays the foundation for quantitation of enteroviral RNA in clinical specimens and establishes a technique that can readily be applied to the diagnosis of enteroviral infection.

Classification of respiratory tract picornavirus isolates as enteroviruses or rhinoviruses by using reverse transcription-polymerase chain reaction

The classification of picornaviruses isolated from respiratory secretions as human rhinoviruses (HRVs) or enteroviruses (EVs) by using reverse transcription-polymerase chain reaction was compared to that derived from acid lability testing. Of the 135 clinical isolates examined, 91 were found to be HRVs and 44 were EVs. There was 100% concordance between the two classification methods. Reverse transcription-polymerase chain reaction is an effective alternative to traditional methods for differentiating HRVs from EVs.

Nested polymerase chain reaction for high-sensitivity detection of enteroviral RNA in biological samples

A method based on nested polymerase chain reaction was developed for the detection of enteroviral genomes in biological samples. By taking advantage of the conserved 5' noncoding region of the enteroviral RNA, two sets of primers were utilized, enabling the detection either of a broad range of enteroviruses or of group B coxsackieviruses only. The sensitivity of the method is close to the detection of single molecules of viral RNA in as much as 1 mg of tissue sample. A preliminary study showed the usefulness of this technique for the analysis of endomyocardial biopsy samples from patients with idiopathic dilated cardiomyopathy and myocarditis.

Detection of enteroviruses in groundwater with the polymerase chain reaction

Standard methods for the detection of enteroviruses in environmental samples involve the use of cell culture, which is expensive and time-consuming. The polymerase chain reaction (PCR) is an attractive method for the detection of enteroviruses in water because primary cell culture is not needed and the increased sensitivity of PCR allows detection of the low numbers of target DNAs and RNAs usually found in environmental samples. However, environmental samples often contain substances that inhibit PCR amplification of target DNA and RNA. Procedures that remove substances that interfere with the amplification process need to be developed if PCR is to be successfully applied to environmental samples. An RNA-PCR assay for the detection of enteroviruses in water was developed and used to test a variety of groundwater concentrates and humic acid solutions seeded with poliovirus type 1. The groundwater samples and humic acid solutions were treated with Sephadex G-50, Sephadex G-100, Sephadex G-200, Chelex-100 resin, and a mixed bed resin to remove PCR-inhibitory material from the samples. Sephadex G-100 in combination with Chelex-100 was found to be very effective in removing inhibitory factors for the detection of enteroviruses in groundwater concentrates by PCR. Viruses were detected in two of the groundwater concentrates by the RNA-PCR assay after treatment with Sephadex G-100 plus Chelex-100. This was confirmed by tissue culture, suggesting that the treatment protocol and, subsequently, the RNA-PCR assay are applicable for the detection of enteroviruses in environmental samples.

Complete nucleotide sequence of a coxsackie B5 virus and its relationship to swine vesicular disease virus

We report the first complete nucleotide sequence of the picornavirus coxsackievirus B5 (CB5), strain 1954/UK/85, an isolate from a case of hand-foot-and-mouth disease. We have compared the sequence with those of other coxsackie B viruses, coxsackievirus A9, poliovirus and swine vesicular disease virus (SVDV). The genes encoding the three major capsid proteins are most closely related to those of SVDV but the 5' and 3' noncoding regions and the P3 gene are more similar to the corresponding regions in the other coxsackie B viruses than to those of SVDV. These observations are considered in the light of the antigenic and biochemical relationships between SVDV and CB5.

Use of cRNA digoxigenin-labelled probes for detection of enteroviruses in humans and in the environment

A dot blot hybridization test for enteroviruses is described using non-radioactive digoxigenin-labelled probes and a chemiluminescent detection. The use of a 5' non-coding riboprobe which detects all enteroviruses and a VP1 probe that detects the three serotypes of polioviruses allows the rapid detection of polioviruses and non-polio enteroviruses in human specimens or environmental water samples. The assay is strictly enterovirus specific and sensitive (800 fg RNA) and offers several advantages over conventional diagnosis or radioactive probes.

Peptide antisera targeted to a conserved sequence in poliovirus capsid VP1 cross-react widely with members of the genus Enterovirus

Rabbits were immunized with synthetic peptides derived from an immunodominant region of the VP1 capsid protein of enteroviruses. This region shows a high degree of homology among all sequenced members of the genus. Peptide-induced antisera were used for immunoperoxidase staining of cell cultures infected with 41 different serotypes of enterovirus. Specific cytoplasmic staining was readily seen in all but two cases. Echovirus type 22 was previously known to differ genetically from the rest of the enteroviruses, and hence, a negative result was expected. Surprisingly, one of the tested serum samples reacted with echovirus 22-infected cells. Coxsackievirus A7-infected cells could be reliably stained with only one of the tested serum samples. For the remaining 39 serotypes, scattered infected cells resulting from 1 to 2 days of incubation with diluted inocula were easily scored as positive before the cytopathic effect became visible. The same antibodies were also used in a sandwich-type enzyme immunoassay to demonstrate poliovirus antigens in cell extracts as early as 3 h after a high-multiplicity infection. These antibodies are candidates for enterovirus group reagents, being potentially useful in both the laboratory diagnosis of enterovirus infections and research on enterovirus-host interactions.

Molecular epidemiology of a variant of coxsackievirus A24 in Taiwan: two epidemics caused by phylogenetically distinct viruses from 1985 to 1989

In order to know the phylogenetic relationship and the route of transmission of a variant of coxsackievirus A24 (CA24v), an agent that caused four sequential outbreaks of acute hemorrhagic conjunctivitis from 1985 to 1989 in Taiwan, the nucleotide sequence variations in the virus-encoded proteinase 3C region (549 nucleotides) were studied with 19 isolates. The prototype strain (EH24/70), four isolates from Japan, and two isolates from Hong Kong were used for comparison. The nucleotide sequences of the Taiwan strains from the 1985-1986 and 1988-1989 epidemics were closely related within each epidemic, while they were more distantly related between strains from two epidemics. Phylogenetic analysis by the unweighted pairwise grouping method of the arithmetic average revealed that the 19 Taiwan isolates had diverged into two groups, 1985-1986 and 1988-1989 groups. The time at which these two groups diverged was estimated to be around May 1982, more than 3 years prior to the first appearance of the CA24v epidemic in Taiwan. On each occasion, the viruses caused a 2-year epidemic and then disappeared. The Taiwan isolates from 1985 to 1986 were closely related to the Japan isolates from 1985 to 1986 and the Taiwan isolates from 1988 to 1989 were phylogenetically close to the 1989 Japan isolates, indicating that Taiwan and Japan had two common-source outbreaks. However, none of the 1988 Taiwan isolates were phylogenetically close to the 1988 Japan or Hong Kong isolates. The evidence revealed that Taiwan has had two repeated but discontinuous introductions of CA24v since its first appearance in Taiwan in 1985. None of the other CA24v strains have been detected so far.

Single-stranded genomic RNA from turkey enterovirus-like virus

Previously, we described a disease syndrome in young turkeys caused by an enterovirus-like virus. The virus was designated an enterovirus-like virus based on size, morphology, and intracytoplasmic crystalline arrays of virus. In the present study, further characterization of the virus was performed to ascertain its classification. The virus has a buoyant density of 1.33 g/ml in CsCl and single-stranded RNA genome of approximately 7.5 kilobases. These combined characteristics indicate that this agent is an enterovirus.

Rapid detection of poliovirus by reverse transcription and polymerase chain amplification: application for differentiation between poliovirus and nonpoliovirus enteroviruses

This report describes a rapid method of detection of poliovirus from viral isolates of clinical specimens using a single set of primers selected from the conserved 5' noncoding region of the poliovirus genome. Of the 144 clinical viral isolates examined, 81 were positive for polioviruses and 50 were positive for nonpoliovirus enteroviruses by tissue culture neutralization and infectivity. All 81 (100%) of the viral isolates identified as poliovirus by tissue culture infectivity were also positive by polymerase chain reaction. Of 50 nonpoliovirus enterovirus isolates found to be negative for poliovirus by tissue culture neutralization and infectivity, 48 were also negative by polymerase chain reaction. The high sensitivity (100%) and specificity (96%) of the primer set indicate that this assay has potential clinical applicability in the diagnosis of nonpoliovirus enterovirus infection.

Detection of enteroviral genome and its significance in cardiomyopathy

Myocarditis is an important disease that can lead to dilated cardiomyopathy (DCM). Using the polymerase chain reaction (PCR), we examined whether viral genomes were present specifically in the hearts of viral myocarditis or DCM patients in our autopsy series and compared the results with their clinicopathological features. We applied three different criteria of myocarditis to fully describe the histological features. The presence of a viral genome was detected by PCR but was not specific in DCM or myocarditis. PCR might be helpful in the diagnosis of viral myocarditis, when combined with other clinical information.

Pathogenetic differences between coxsackie A and B virus infections in newborn mice

Coxsackieviruses are divided into A and B subgroups on the basis of their pathogenicity in newborn mice. Although used in the classification of these viruses, our understanding of the details of the infection is incomplete due to the lack of sensitive and specific techniques to localize the viruses in affected tissue. We have used in situ hybridization to detect coxsackievirus genomes in tissues of newborn mice after infection by five serotypes (A2, A9, A21, B3 and B4) through different administration routes. Our results indicate that coxsackie A viruses are able to affect both skeletal and heart muscle while the coxsackievirus B subgroup infects a wide range of tissues. In addition to striated muscle these include central nervous system, liver, exocrine pancreas and brown fat. This model will make it possible to analyze molecular factors determining tissue tropism.

Failure to demonstrate enterovirus aetiology in Swedish patients with dilated cardiomyopathy

Attempts were made to establish a possible relationship between enterovirus infection and dilated cardiomyopathy (DCM) by use of serology, virus isolation from faecal samples, and detection of enteroviral RNA in endomyocardial biopsies (EMB) by the polymerase chain reaction (PCR). Sera from 63 patients with DCM and matched controls were examined for enterovirus infection by mu-capture IgM and indirect IgG ELISA. Thirty-six patients were further tested for the presence of enterovirus group-specific antigen (VP1) in an immunoassay system. The results were consistently negative. Faecal samples from 35 of these patients were negative by enterovirus isolation both when samples were cultured directly and after acid treatment. EMB from 35 patients were examined for enteroviral RNA by PCR; none of the samples was reactive. In conclusion, the results fail to indicate involvement of enteroviruses in the aetiology of DCM.

Rapid diagnosis of enterovirus infection by magnetic bead extraction and polymerase chain reaction detection of enterovirus RNA in clinical specimens

We describe a rapid method for extraction and detection of enterovirus RNA in clinical samples. By using magnetic bead technology, enterovirus RNA was efficiently and rapidly extracted from cerebrospinal fluid, stool, saliva, blood, pericardial fluid, urine, and cryopreserved or formalin-fixed solid tissue. Enterovirus RNA was then detected by reverse transcription followed by polymerase chain reaction amplification with primers designed to allow detection of most enterovirus serotypes. For detection of enteroviruses in specimens from patients with acute enteroviral disease, the overall sensitivity of enzymatic RNA amplification was greater than that of cell culture isolation, especially in blood specimens and in stool specimens from patients with acute cardiac disease. Enterovirus RNA was also detected in cryopreserved and archival formalin-fixed myocardial tissue from patients with acute myocarditis and chronic dilated cardiomyopathy. The ability to study archival specimens is of particular value in conducting retrospective investigation. The RNA extraction procedure used was considerably faster than extraction methods using organic reagents, used less hazardous reagents, and was of similar sensitivity. This detection protocol may therefore be useful both for the diagnosis of enterovirus infection and in studying the pathogenesis of acute and chronic enterovirus-induced disease.