[Myocarditis and cardiomyopathy]

In situ hybridization studies have shown that myocardial enterovirus infections may be detected in acute and chronic enterovirus-induced myocarditis, indicating the possibility of myocardial enterovirus persistence in the human heart. As well, such infections can be observed in patients with dilated cardiomyopathy, a condition which may evolve from chronic myocarditis. The discovery of possible enterovirus persistence in the human heart is supported by the finding in different strains of immunocompetent mice, demonstrating that coxsackievirus B3, typically a cytolytic enterovirus, is capable of evading immunological surveillance in a host-dependent fashion, thus inducing a persistent type of heart muscle infection. Progress is currently being made in unraveling the molecular mechanisms of enterovirus persistence, the diversity of host and virus genetics and their impact on the nature and severity of myocardial injury. Apart from providing an etiologic diagnosis, there are therapeutic implications from in situ demonstration of myocardial enterovirus infection. Evaluation of specific antiviral agents, for example interferons, may lead to the development of new therapeutic strategies capable of providing protection against myocardial enterovirus infection.

Coxsackieviral proteins functionally recognize the polioviral cloverleaf structure of the 5'-NTR of a chimeric enterovirus RNA: influence of species-specific host cell factors on virus growth

The 5'-non-translated region (NTR) of enteroviruses contains secondary structures which do not only serve in the initiation of translation but also in the initiation of plus-strand RNA synthesis by binding of viral and cellular proteins. To investigate a very early step of enteroviral replication by cis- and trans-complementation, 220 nucleotides of the 5'-region of coxsackievirus B3 (CVB3) were exchanged with the corresponding region of poliovirus type 1 (PV1) to yield the chimeric virus CVB3[PV5']. The viability of this chimera demonstrates that the polioviral cloverleaf structure of the 5'-NTR is functional in the replication of a chimeric CVB3 RNA. The HeLa-generated chimera reveals a 4-nucleotide deletion (nt 232-235) within a short direct repeat. Besides clearly reduced growth characteristics in all permissive cell lines, the chimera exhibits a small-plaque phenotype. The host range is changed since the virus grows well in human HeLa cells, but does not replicate in murine YAC-1 and Ltk cells, although these cell lines are permissive for the replication of both parental viruses. Moreover, in simian Vero, COS-1, or FRhK-4 cells the HeLa-generated chimera CVB3[PV5'] exhibits a strict temperature sensitivity at 39 degrees C. After infection of simian cells with high m.o.i. in situ hybridization data reveal that the chimera replicates in single cells at almost normal rates indicating that only a small fraction of HeLa-generated virus is able to multiplicate in simian cell lines. After passaging the virus chimera in Vero cells two further mutations occur at nucleotide positions 185 and 227. Since this genome region is known to interact with viral proteins and several host cell factors during the initiation of replication and translation, interactions of such factors with either viral RNA or viral proteins may be disturbed but still functional at permissive temperatures in HeLa cells and simian cell lines, whereas murine cell lines are not permissive. These experiments suggest that phenomena like host range, tissue tropism and cell-type specificity may be explained as a complex interplay of cellular surface receptors and intracellular host factors. Such intracellular factors could be part of the enteroviral initiation complex during the plus-strand RNA synthesis or during translation initiation and could be expressed in a tissue-, organ- or species-specific way or might be regulated developmentally.

Enterovirus-infected immune cells of spleen and lymph nodes in the murine model of chronic myocarditis: a role in pathogenesis?

Molecular hybridization studies have demonstrated that human enteroviruses, including group B coxsackieviruses (CVB), are detectable not only in endomyocardial biopsies of patients with acute enterovirus myocarditis but also in those with chronic disease. Such infections are observed in some patients with end-stage dilated cardiomyopathy, indicating the possibility of persistent heart muscle infection. Enterovirus persistence in the human heart is supported by the recent discovery in various murine models of enterovirus myocarditis that chronic inflamed heart muscle lesions are consistently associated with enterovirus persistence. Application of in-situ hybridization in a multiorgan study of CVB3-infected immunocompetent mice now reveals that, in addition to the myocardium, spleen and lymph nodes are persistently infected. During acute myocarditis, the majority of infected spleen cells was found to be located within the follicles of spleen and lymph nodes. At later stages of the disease, enteroviral infection was shown to be restricted to cells of the germinal centre in secondary follicles of spleen and lymph nodes. Thus, infected immunocompetent cells may play an important role in dissemination of the virus in the host and maintenance of a non-cardiac viral reservoir.

Characterization of a 100-kilodalton binding protein for the six serotypes of coxsackie B viruses

Viral infection of host cells primarily depends on binding of the virus to a specific cell surface protein. In order to characterize the binding protein for group B coxsackieviruses (CVB), detergent-solubilized membrane proteins of different cell lines were tested in virus overlay protein-binding assays. A prominent virus-binding protein with a molecular mass of 100 kDa was detected in various CVB-permissive human and monkey cell lines but was not detected in nonpermissive cell lines. The specificity of CVB binding to the 100-kDa protein on permissive human cells was substantiated by binding of all six serotypes of CVB and by competition experiments. In contrast, poliovirus and Sendai virus did not bind to the 100-kDa CVB-specific protein. A fraction of HeLa membrane proteins enriched in the range of 100 kDa showed functional activity by transforming infectious CVB (160S) into A-particles (135S). In order to purify this CVB-binding protein, solubilized membrane proteins from HeLa cells were separated by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by elution of the 100-kDa protein. Amino acid sequence analysis of tryptic fragments of the CVB-binding protein indicated that this 100-kDa CVB-specific protein is a cell surface protein related to nucleolin. These results were confirmed by immunoprecipitations of the CVB-binding protein with nucleolin-specific antibodies, suggesting that a nucleolin-related membrane protein acts as a specific binding protein for the six serotypes of CVB.

Cultured human myocardial fibroblasts of pediatric origin: natural human interferon-alpha is more effective than recombinant interferon-alpha 2a in carrier-state coxsackievirus B3 replication

Cultured human myocardial fibroblasts of pediatric origin seem to be a useful species-specific model for studying various heart diseases which involve the myocardial interstitium, for example enterovirus heart disease. Cells were propagated from small samples of human ventricular tissues (0.2 g) obtained from standard surgical procedure for the correction of Fallot-tetralogy. Cultured cells exhibited typical fibroblastoid morphology over a period of 4 months and were uniformly immunoreactive with a monoclonal antibody directed against prolyl-4-hydroxylase, a marker enzyme of fibroblasts. Infection of cell cultures with coxsackievirus B3, a cardiotropic enterovirus, resulted in a typical carrier-state type of virus persistence. Average virus titers of 2.3 x 10(5) plaque-forming units/ml (SD = 9.9 x 10(4)) were maintained over a period of up to 10 weeks by productive infection of about 8-10% of the cell population. Coxsackievirus B3 carrier cultures of human myocardial fibroblasts were used to evaluate in vitro the long-term antiviral effects of recombinant interferon alpha-2a and natural human interferon-alpha. Recombinant interferon-alpha reduced virus yields by 90% with a concentration of 423 IU/ml, whereas with natural interferon-alpha a 90% reduction of virus yields was achieved with concentrations as low as 21 IU/ml. Antiviral effects of both recombinant and natural interferon-alpha were highly specific and not related to inhibition of cell-proliferation (< 50% with interferon-alpha concentrations as high as 6250 IU/ml). Since effective concentrations of interferon-alpha can be easily attained in vivo with subcutaneous application, interferon-alpha (in particular: natural interferon-alpha) may become useful in the treatment of patients with enterovirus myocarditis and enterovirus induced dilated cardiomyopathy.

The inhibitory effect of astragalus membranaceus on coxsackie B-3 virus RNA replication

Using mice infected with coxsackie B-3 virus (CVB3) as a viral myocarditis model, we observed the inhibitory effect of Astragalus membranaceus (AM) on CVB3-RNA replication in myocardial tissue of mice by RNA-RNA in situ hybridization with negative-strand RNA probes labelled with 35S and quantitative imaging analysis of positive signals. The mechanism of its effect on CVB3-RNA replication has been investigated by detection of beta-interferon (beta-IFN) as well. Results showed that the copy numbers of CVB3-RNA as well as the histologic scores (necrosis) in myocardial tissues of infected-AM treated mice were significantly lower than those in infected and normal saline treated mice, suggesting that AM could inhibit the replication of CVB3-RNA, but its effect on CVB3-RNA replication had no correlation with induction of beta-IFN.

Infrequency of cytomegalovirus genome in coronary arteriopathy of human heart allografts

In heart transplantation, long-term engraftment success is severely limited by the rapid development of obliterative disease of the coronary arteries. Data from various groups have been suggestive of a pathogenetic role of herpesviruses, particularly human cytomegalovirus, in accelerated allograft coronary artery disease; however, results are not yet conclusive. This study examines the hypothesis that human cytomegalovirus infection of allograft tissues is related pathogenetically and directly to accelerated coronary artery disease. Using in situ DNA hybridization and polymerase chain reaction, we examined particular coronary artery segments from 41 human heart allografts (ranging from 4 days to greater than 4 years after transplantation; mean, 457 days) and 22 donor age- and gender-comparable, coronary site-matched trauma victims for presence of human cytomegalovirus DNA. Human cytomegalovirus genome was detected in 8 of 41 (19.5%) allografts and in 1 of 22 (4.5%) control hearts. This difference in positivity was not statistically significant (P = 0.10). In the human cytomegalovirus-positive hearts, viral genome was localized to perivascular myocardium or coronary artery media or adventitia. Human cytomegalovirus genome was not detected in arterial intima of any allograft or control heart, although human cytomegalovirus genome was readily identified within intima of small pulmonary arteries from lung tissue with human cytomegalovirus pneumonitis. By statistical analyses, the presence of human cytomegalovirus genome was not associated with the nature or digitized extent of transplant arteriopathy, evidence of rejection, allograft recipient or donor serological data suggestive of human cytomegalovirus infection, duration of allograft implantation, or causes of death or retransplantation. Thus, our data indicate a low frequency of detectable human cytomegalovirus genome in accelerated coronary artery disease and do not support a direct role for human cytomegalovirus in vascular wall infection or in the development of accelerated coronary artery disease.

Characterization of a cardiac-selective and developmentally upregulated promoter in transgenic mice

Transcriptional regulatory mechanisms which mediate cardiac-specific gene expression have not yet been completely understood. Potential cardiac-specific promoter sequences, sharing similar protein binding motives, show either coexpression in skeletal muscle, local restriction to the atrium or late onset of expression during fetogenesis. Based on in situ hybridization studies that indicated the expression of the cardiac myosin-light-chain-2 (MLC-2) gene in ventricular myocardium and in the lower outflow tract, a model system for selective targeting of foreign genes to the heart of transgenic mice has been developed. The regulatory promoter element was derived from the rat cardiac MLC-2 gene. 2100 bp of the 5' regulatory MLC-2 sequences were found to drive constitutive cardiac expression of a firefly luciferase reporter gene from early tubular heart formation. During ventricular loop and septum formation luciferase activity was 10-fold upregulated in comparison to steady-state levels observed 10 days after birth. No luciferase activity was detectable in any other muscle or non-muscle tissue of transgenic mice. These data suggest that the 2.1 kb DNA sequences of the 5' flanking region of the cardiac MLC-2 gene contain sufficient regulatory elements for a selective gene expression in cardiac myocytes from embryogenesis. The transgenic model should aid in determining the influences of pathogenic gene products on developing and mature heart muscle to elucidate the etiology of myocardial diseases such as cardiomyopathies.

Characterization of the N-terminal part of the neutralizing antigenic site I of coxsackievirus B4 by mutation analysis of antigen chimeras

Coxsackievirus B3 (CVB3) as a potential RNA virus vector for the presentation of foreign antigenic epitopes was further characterized. Insertion mutagenesis of infectious CVB3 cDNA yielded viable antigen chimeras containing variant BC loops of VP1 of coxsackievirus B4 (CVB4). Analysis of three antigen chimeras allowed the mapping of the N-terminal part of the neutralizing antigenic site 1 (N-Ag1) of CVB4 which is located in the BC loop of the structural protein VP1. A significant neutralization of a viable chimera with the deletion of CVB4-specific amino acid Ser-83 at the amino terminus of the VP1 BC loop was obtained with CVB4 serotype-specific polyclonal antisera. This neutralization was reduced after further deletion of the adjacent Ala-84, suggesting that this amino acid either constitutes the beginning of N-Ag1 of CVB4 or is essential for the conformation of the adjacent epitope. In contrast, exchange of amino acid Ser-86 to alanine, in the middle of the BC loop, led to complete loss of reactivity with CVB4-specific antibodies, demonstrating the importance of this residue for binding of CVB4 neutralizing antisera. Furthermore, we observed that manipulations of the VP1 BC loop resulted in increased thermolability of the viable chimeras in comparison to CVB3, although replication efficiencies were similar.

[Effect and mechanism of Astragalus membranaceus on coxsackie B3 virus RNA in mice]

Using Balb/c mice infected with Coxsackie virus B3 (CVB3) as a model, the effect of Astragalus membranaceus (AM) on CVB3-RNA has been observed in myocardial tissues of mice by RNA-RNA in situ hybridization with negative-strand RNA probes leballing with 35S and quantitative imaging analysis of positive hybridization signals. The mechanism of its effect on CVB3-RNA has also been investigated by induction with AM and detection of beta-interferon (beta-IFN). Results showed that the copy numbers of CVB3-RNA as well as the histologic necrotic sizes in myocardial tissues of AM treated infected mice were significantly smaller than that in infected normal saline treated mice (P < 0.01, P < 0.05) respectively, suggesting that AM could inhibit the replication of CVB3-RNA, but its effect on CVB3-RNA was not correlated with induction of beta-IFN.

Enterovirus-induced myocarditis: hemodynamic deterioration with immunosuppressive therapy and successful application of interferon-alpha

In 1985, myocarditis was diagnosed by endomyocardial biopsy in a 53-year-old woman who was free of symptoms of heart insufficiency. Immunosuppressive therapy with azathioprine and prednisolone was prescribed as the patient had deteriorated to NYHA II heart insufficiency in March 1986. When application of immunosuppressive agents was terminated in 1987, serial endomyocardial biopsies revealed no signs of myocarditis, thus indicating effectiveness of immunosuppression. Nevertheless, the patient had worsened clinically and hemodynamically. At follow-up in 1991, the patient had progressed to dilated cardiomyopathy resulting in NYHA III heart insufficiency. Enterovirus infection of the heart was detected by in situ nucleic acid hybridization. In addition, retrospective serology indicated a significant increase of coxsackievirus B2 antibodies between 1985 and 1991. Investigational antiviral therapy with recombinant interferon alpha-2a was tolerated well and a favorable clinical, hemodynamic, and virologic response was observed. Thus, progression of biopsy-proven myocarditis to dilated cardiomyopathy may have been facilitated by immunosuppressive therapy in enterovirus infection. Antiviral therapy might be advantageous in patients with enterovirus myocarditis and dilated cardiomyopathy.

Investigation of the coxsackievirus B3 nonstructural proteins 2B, 2C, and 3AB: generation of specific polyclonal antisera and detection of replicating virus in infected tissue

The coxsackievirus B3 (CVB3) nonstructural proteins 2B and 3AB were synthesized as beta-galactosidase fusion proteins in E. coli in order to generate specific polyclonal antisera. 2B and 3AB fusion proteins were purified by preparative SDS-polyacrylamide gel electrophoresis and inoculated into rabbits. Protein 2C-specific antiserum was produced using synthetic oligopeptides which were defined by computer based amino acid sequence analysis. Specificity of the generated antisera was analysed by immunoblotting, immunofluorescence, immunohistochemistry and immunoelectron microscopy. All antisera allowed specific detection of the viral proteins 2B, 2C, and 3AB in CVB3-infected cells as well as in myocardial and pancreatic tissue of CVB3-infected mice. In addition, the CVB3 2C-specific antiserum was shown to be highly cross-reactive with the analogous protein of other picornaviruses, including cardiotropic enterovirus serotypes such as coxsackievirus A9, coxsackievirus B (types 1-5), and echovirus 11. Moreover, the immunological detection of nonstructural proteins enables diagnosis of replicating virus in infected tissue. These results demonstrate that the generated antisera are valuable tools for diagnostic approaches. Furthermore, they may help to elucidate the role of the nonstructural proteins 2B, 2C, and 3AB in enteroviral replication and pathogenesis.

[Mechanisms of re-stenosis after angioplasty]

Restenosis post angioplasty is a segmentally limited, wound healing response to a circumscript traumatization of the vascular wall associated with the therapeutic intervention, which also comprises residual or recoiling plaque components at the time of initial revascularization. Studies with animal models and the analysis of human plaque tissue harvested by autopsy or atherectomy indicate a cascade-like course of this wound healing reaction, in which initially different cell types such as thrombocytes, endothelial cells, monocytes/macrophages and smooth muscle cells (SMCs), later predominantly SMCs are involved. In the first phase of inflammation, angioplasty as a multifactorial stimulus induces a sequence of (a) destruction of endothelial and subendothelial structures, (b) traumatization of medial regions with rupture of the internal elastic lamina, (c) exposition of thrombogenic factors such as collagen or tissue factor, (d) stretching of smooth muscle cells with subsequent expression of proto-oncogens (c-fos, c-myc, c-myb), (e) release of growth factors from cells of the bloodstream, endothelial cells and SMCs by direct traumatization and segmental thrombus formation, and (f) thrombin production with autocatalytic activation of the SMC thrombin receptor. Overlapping the inflammation period, granulation begins 3 days after angioplasty. Proteinases such as plasmin as well as collagenases induce the disintegration of extracellular matrix structures, thereby modulating plaque formation, and lead to an organelle-rich SMC phenotype within the intima and media. The phenotypic alteration of SMCs is considered to be the prerequisite for mitogenic and migratory stimulation. This stage shows different expression patterns of growth factors and their receptors; however, there is only limited knowledge about spatiotemporal and maximal expression as well as their coordination for human vascular wall tissue (PDGF, PDGF-R, EGF-R, FGF, FGF-R, TGF-beta). Overlapping with the granulation period, induction of different components of the extracellular matrix occurs 1-2 weeks after angioplasty, possibly mediated by TGF-beta (phase of matrix formation). Smooth muscle cells produce and secrete matrix proteins such as tenascin, fibronectin, collagens and proteoglycans, and thereby induce a marked increase of the neointimal plaque volume. Angiographic restenoses of coronary and peripheral arteries histologically exhibit tissue with high cellularity (> 500 cells/mm2), associated with SMC activity markers such as PCNA or NMMHC-B. Proliferative and migratory activities of these cells in vitro are augmented by a factor of 2 to 3 as compared to those from chronic primary lesions. Transmission electron microscopic analysis proves that within the media a nearly complete re-differentiation of SMCs occurs, whereas intimal SMCs persist in the intermediate phenotype.(ABSTRACT TRUNCATED AT 400 WORDS)

Attenuation of a reactivated cardiovirulent coxsackievirus B3: The 5'-nontranslated region does not contain major attenuation determinants

To investigate the molecular basis of pathogenicity of Coxsackieviruses, a virus was reactivated by transfection from a full-length cDNA clone derived from cardiovirulent Coxsackievirus B3 (CVB3). The reactivated virus, rCVB3, was passaged serially in human dermatofibroblasts (HDF). No cytopathic effect was observed up to 12 days after inoculation with rCVB3 or early-passage virus, although disintegration of the monolayers was observed with late-passage virus (10th to 14th passages). Approximately 10% of HDF inoculated with rCVB3 were positive for viral antigens by immunofluorescence using enterovirus- or CVB3-specific monoclonal antibodies. These observations, together with the low infectivity titre of rCVB3 in HDF, suggests that HDF initially support only carrier state infection. After the 14th passage, the cardiovirulence of passaged virus (p14V) in mice was attenuated by a factor of > 10(4). Phenotypic changes of plaque size were also noticed in p14V: An attenuated variant (p14V-1) that produced larger plaques than rCVB3 in Vero cells has been plaque purified. The 5'-terminus of the genome of attenuant p14V-1 was amplified by polymerase chain reaction (PCR) and its sequence determined. Only one point mutation was found within the 5'-nontranslated region (5'NTR) at position 690 (A to U) compared to the viral RNA sequence obtained for rCVB3. An intertypic chimeric virus was reactivated from a cDNA clone after replacing the 5'-terminal 891 nucleotides of the wild-type genome with the corresponding region of the attenuant p14V-1. This chimeric virus, CB3/p14V-1/1, produced wild-type plaques in Vero cells and showed cardiovirulence similar to that of rCVB3 in mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Heart-specific targeting of firefly luciferase by the myosin light chain-2 promoter and developmental regulation in transgenic mice

Based on hybridization studies indicating constitutive expression levels of the endogenous myosin light chain-2 (MLC-2) gene in embryonic, fetal, and adult myocardium, a model system for selective targeting of genes to the heart of transgenic mice has been developed. A 2.1-kb DNA fragment of the 5' flanking region of the rat cardiac MLC-2 gene was fused to the firefly luciferase reporter gene and introduced into fertilized mouse oocytes. In four independent transgenic mouse lines, the expression of the MLC-2-luciferase fusion gene was found exclusively in heart muscle. In contrast to the endogenous MLC-2 gene, no luciferase activity was detectable in slow-twitch skeletal muscle or any other tissue of transgenic mice. This result suggests that the 2.1-kb DNA fragment of the 5' flanking region of the cardiac MLC-2 gene contains the regulatory elements required for selective gene expression in cardiac myocytes in vivo. In contrast to the endogenous steady-state MLC-2 expression during development, transgenic luciferase activity was 10-fold higher during embryogenesis, when formation of the ventricular loop and septum takes place. The enhanced luciferase activity in early heart development may suggest a growth-dependent control mechanism, involving either transcriptional or posttranscriptional regulation. In conclusion, this model system with the 2.1-kb ventricle-specific MLC-2 promoter sequence should facilitate the overexpression of gene products in the developing and mature heart muscle and further elucidate molecular mechanisms of myocardial diseases such as cardiomyopathies.

Molecular biology of viral heart disease

In situ hybridization studies have proved that myocardial enterovirus infections are detectable in all stages of acute and chronic enterovirus-induced myocarditis as well as in some patients with end-stage dilated cardiomyopathy, suggesting the possibility of myocardial enterovirus persistence. Possible enterovirus persistence in the human heart is supported by the discovery of enterovirus persistence in different murine models of chronic myocarditis, demonstrating that coxsackie-virus B3, typically a cytolytic enterovirus, is capable of evading immunological surveillance in a host-dependent fashion. Progress is currently being made in unraveling the molecular mechanisms of enterovirus persistence, the diversity of host and virus genetics and their impact on the nature and severity of the disease. Apart from providing an etiologic diagnosis, there are therapeutic implications from in situ demonstration of myocardial enterovirus infection. Evaluation of specific antiviral agents, for example interferons, may lead to the development of new therapeutic strategies capable of providing protection against myocardial enterovirus infection.

Myocardial indium-111 antimyosin uptake in patients with idiopathic dilated cardiomyopathy: its relation to haemodynamics, histomorphometry, myocardial enteroviral infection, and clinical course

The myocardial uptake of indium-111 antimyosin indicates the presence of ongoing myocyte damage. To evaluate the role of this finding in patients with idiopathic dilated cardiomyopathy (IDC), 36 patients were studied by planar and SPECT antimyosin imaging. The diagnosis of IDC was based on coronary angiography and left ventricular endomyocardial biopsy. The antimyosin scan was evaluated qualitatively from SPECT images and assessed quantitatively by a count density index (CDI) which measured the tracer activity over the heart relative to the lung and sternal region (normal value less than 1.20). Group 1 consisted of 13 patients (36%) with an increased myocardial antimyosin uptake, while 23 patients had a normal antimyosin scan (group 2). Clinical data, pulmonary artery pressures, gated blood pool ejection fraction and histomorphometry of endomyocardial biopsies were similar in both groups. During a follow-up of 21 +/- 12 months there were two cardiac deaths in group 1 and 10 deaths in group 2 (P = 0.12). The 2-year survival rate was 81% and 59%, respectively. During follow-up, there was no significant change in haemodynamic parameters in either group, but there was a slight improvement in functional NYHA class in group 1 (P < 0.05). No association was found between the presence of myocardial enterovirus infection, determined in 17 patients by in situ hybridization and the antimyosin scan (P = 0.5 g). Myocardial antimyosin uptake was found in a high percentage of patients with IDC, indicating ongoing myocyte damage. This finding was not related to any clinical, haemodynamic, morphological parameter, or enterovirus infection. Myocyte damage is a distinct feature in a subgroup of patients with IDC unrelated to any known causes of myocellular destruction. This subgroup showed a trend towards a more favourable clinical outcome.

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.

Molecular pathogenesis of enterovirus-induced myocarditis: virus persistence and chronic inflammation

In situ hybridization studies have proved that myocardial enterovirus infections are detectable in all stages of acute and chronic enterovirus-induced myocarditis as well as in some patients with end-stage dilated cardiomyopathy, suggesting the possibility of myocardial enterovirus persistence. Possible enterovirus persistence in the human heart is supported by the discovery of enterovirus persistence in different murine models of chronic myocarditis, demonstrating that coxsackievirus B3, typically a cytolytic enterovirus, is capable of evading immunological surveillance in a host-dependent fashion. Progress is currently being made in unraveling the molecular mechanisms of enterovirus persistence, the diversity of host and virus genetics and their impact on the nature and severity of the disease. Apart from providing an etiologic diagnosis, there are therapeutic implications from the in situ demonstration of myocardial enterovirus infection. Evaluation of specific antiviral agents, for example interferons, may lead to the development of new therapeutic strategies capable of providing protection against myocardial enterovirus infection.

Synergistic interaction of interferon-beta and interferon-gamma in coxsackievirus B3-infected carrier cultures of human myocardial fibroblasts

The antiviral effects of human interferon-beta (IFN-beta) and human recombinant interferon-gamma (rIFN-gamma) were studied in persistently coxsackievirus B3-infected carrier cultures of human myocardial fibroblasts over a period of 21 days. Synergism was observed with concentrations as low as 30 IU of IFN-beta plus 10 IU of rIFN-gamma/mL, reducing mean viral titers from 6.0 x 10(7) to 1.3 x 10(4) pfu/mL and number of infected cells from 14.4% to 0.1% as determined by quantitative in situ hybridization. Higher concentrations of IFNs (both > or = 30 IU/mL) were associated with transient antagonism followed by antiviral synergism. With 100 IU of IFN-beta plus 30 IU of rIFN-gamma/mL, elimination of infectious virus was consistently achieved and sustained for 6 weeks after cessation of IFN application, whereas at least threefold higher concentrations were required with single drugs. In summary, our data support a concept of low-dose IFN combination schedules that might become useful in the treatment of enteroviral heart disease.

[In situ detection of EGF receptor mRNA in arteriosclerotic lesions in man: implications for the proliferative activity of smooth muscle cells]

Growth factors and growth factor receptors are considered to be key elements in the pathogenesis of arteriosclerosis and restenosis formation. To study the local expression of epidermal growth factor (EGF) receptor, plaque tissue specimens from advanced lesions (10 coronary, two femoral, seven carotid) of 19 patients were taken for in situ hybridization studies using an EGF-specific cDNA probe. In serial vascular sections of three lesions with increased focal cellularity, autoradiographic silver grains were clearly localized to intimal cells adjacent to the internal elastic lamina. EGF mRNA transcripts were not observed in the fibrous cap, the plaque shoulders, necrotic intimal areas, or in the media. In smooth muscle cells (SMCs) cultured from human plaque tissue, EGF increased SMC proliferative activity in a dose-dependent manner (ED50: 3-6 ng of EGF/ml). Proliferative responsiveness to EGF (10 ng/ml) was found to be significantly (p < 0.01) enhanced in coronary SMCs derived from restenotic lesions as compared to those from primary stenoses. The expression of EGF receptor mRNA in human atheromatous lesions could be of prognostic value to predict an increased SMC proliferative response to stimulatory growth factors.

Myosin light chain-2 luciferase transgenic mice reveal distinct regulatory programs for cardiac and skeletal muscle-specific expression of a single contractile protein gene

To examine the relationship between the cardiac and skeletal muscle gene programs, the current study employs the regulatory (phosphorylatable) myosin light chain (MLC-2) as a model system. Northern blotting, primer extension, and RNase protection studies documented the high level expression of the cardiac MLC-2 mRNA in both mouse cardiac and slow skeletal muscle (soleus). Transgenic mouse lines harboring a 2100- or a 250-base pair rat cardiac MLC-2 promoter/luciferase fusion gene were generated, demonstrating high levels of luciferase activity in cardiac muscle, and only background luminescence in slow skeletal muscle and non-muscle tissues. As assessed by in situ hybridization, immunofluorescence, and luminescence assays of luciferase reporter activity in various regions of the heart, both the endogenous MLC-2 gene and the MLC-2 luciferase fusion gene were expressed exclusively in the ventricular compartment, with expression in the atrium at background levels. Point mutations within the conserved regulatory sites HF-1a and HF-1b significantly cripple ventricular muscle specificity, while mutation of the single E-box site was without effect, suggesting that ventricular muscle-specific expression occurs through an E-box-independent pathway. This study provides direct evidence that the cis regulatory sequences in the cardiac/slow twitch MLC-2 gene which confer cardiac and skeletal muscle-specific expression can be clearly segregated, suggesting that distinct regulatory programs may have evolved to control the tissue-specific expression of this single contractile protein gene in cardiac and skeletal muscle.

Mapping of the RD phenotype of the Nancy strain of coxsackievirus B3

The RD variants of group B coxsackieviruses differ from their parental strains in having the ability to replicate in a human rhabdomyosarcoma cell line, RD. The nucleotide sequence of the P1 region of the RD variant of coxsackievirus B3 strain Nancy (CB3NRD) was determined by sequencing cloned cDNAs, obtained by PCR amplification. A comparison between the established nucleotide sequence and that of the P1 region from the parental virus revealed 12 point mutations which corresponded to six amino acid replacements. To identify if the P1 region is responsible for the phenotype of CB3NRD, a chimeric virus was constructed, using an infectious cDNA clone of CB3. The P1 region of the infectious cDNA was replaced by cDNA fragments from CB3N (parental strain Nancy) or CB3NRD and the resulting recombinants were assayed for their ability to infect and replicate in RD cells. The results showed that the RD phenotype of CB3NRD maps in the P1 region. Furthermore, a chimera which only contained the 5' part of the P1 region derived from CB3NRD and the remaining P1 sequence from CB3N was able to replicate in RD cells, suggesting that the VP2 polypeptide contains at least one determinant for the RD phenotype.

Cytomegalovirus and other herpesviruses: do they have a role in the development of accelerated coronary arterial disease in human heart allografts?

In conclusion, a great deal of indirect and inferential data point to herpesviruses as having a role in atherogenesis. It has been shown that the herpesviruses are able to remain within vascular tissue in a latent state, allowing for reactivation to occur with subsequent sequelae of an active infection. Herpesviruses affect the cellular metabolic activity of cells, induce the accumulation of lipids, and inhibit the production of matrix proteins. They have the ability to inhibit endothelial cell binding to the basement membrane. It is also known that the herpesviruses, particularly CMV, can initiate a variety of immunologic responses that may contribute to endothelial damage, precipitating atherogenesis. We are only beginning to understand how CMV may participate in ACAD. Greater attention must be focused on the exact cause-and-effect relationship between CMV infection and ACAD. Even the presence of CMV genomes in arterial walls of allografts must be viewed conservatively in the knowledge of CMV ubiquity and other probable contributions to ACAD. If CMV is involved in the development of ACAD, as an active or latent infection, directly or indirectly, it probably involves numerous coexistent mechanisms (Figure 5).

Migratory activity of human smooth muscle cells cultivated from coronary and peripheral primary and restenotic lesions removed by percutaneous atherectomy

BACKGROUND

The successful cultivation of human smooth muscle cells (SMC) from coronary and peripheral atherosclerotic lesions removed by percutaneous directional atherectomy is described.

METHODS AND RESULTS

Sixty-seven patients in whom plaque material was obtained compose the study population. A total of 73 lesions from both coronary (n = 38) and peripheral (n = 35) arteries of primary (n = 50) and restenotic origin (n = 23) were studied. Successful cultivation was significantly (p less than 0.001) dependent on the quantity of plaque material submitted. Fifty-five percent of patients in whom atherectomy specimens were removed from coronary lesions yielded an adequate SMC population in comparison to 89% of those from peripheral arteries (p less than 0.01). Cultivation was not dependent on the age and sex of patients, lesion origin, risk factors, medications, or incidence of unstable angina. In an attempt to quantify SMC activity, migratory velocity was measured with a computer-assisted motion analysis system. SMC migratory velocity was found to be significantly (p less than 0.001) greater in restenotic than in primary plaque material. This finding was confirmed for both coronary and peripheral lesions.

CONCLUSIONS

Our data suggest that elevated SMC migratory activity may be an important mechanism in the development of restenotic lesions.

Ongoing enterovirus-induced myocarditis is associated with persistent heart muscle infection: quantitative analysis of virus replication, tissue damage, and inflammation

Coxsackievirus B3-induced myocarditis in different immunocompetent mouse strains was used as a model to investigate interrelationships between virus replication and development of chronic enteroviral heart disease. Using in situ hybridization to detect enteroviral RNA, we show that heart muscle infection is not only detected in acute myocarditis but is also detected during the chronic phase of the disease. Coxsackievirus B3 could evade immunological surveillance in a host-dependent fashion, thus inducing a persistent infection of the myocardium in association with ongoing inflammation. Patterns of acute and persistent myocardial infection were quantitatively assessed in one representative mouse strain (A.CA/SnJ, H-2f) by applying computer-assisted digital image processing; these patterns were then related to the extent of myocardial tissue damage as well as to inflammation. We observed a strong correlation, both spatial and temporal, between viral replication and development of myocardial lesions, indicating that acute and chronic myocardial injuries are a consequence of multifocal organ infection. Analysis of strand-specific in situ hybridization revealed that viral replication in persistent infection is restricted at the level of RNA synthesis. The described procedure for quantitating organ infection provides a powerful tool for evaluating virus-host interactions and will be of particular interest to those studying human enterovirus-induced cardiomyopathies.

Natural history of Coxsackievirus B3-induced myocarditis in ACA/Sn mice: viral persistence demonstrated by quantitative in situ hybridization histochemistry

Enteroviruses are considered to be the major aetiological agents of myocarditis in humans. Recent in situ hybridization studies on endomyocardial biopsies and autopsy hearts indicate that enterovirus RNA can be detected (pattern of persistent infection) not only in acute myocarditis (pattern of acute infection), but also in chronic dilated cardiomyopathy. Our experimental studies on murine coxsackievirus B3 myocarditis provided evidence that persistent infection may also occur in mice. Quantitative in situ hybridization and immunohistochemistry as well as electron microscopical in situ hybridization experiments were performed on ACA/SnJ mice 3-30 days after infection. The pattern of acute infection (days 3-9 p.i.) is characterized by rapid progression of myocardial lesions, an increasing number of inflammatory cells and a high number of infected myocytes. Hallmarks of the persistent pattern (days 15-30 p.i.) are reduced inflammation, reduced numbers of persistently infected cells and a slow progression of myocardial lesions. Infection is primarily restricted to degenerated, atrophic myocytes and to fibroblasts.

Progress and challenges in the pathological diagnosis of myocarditis

The pathological diagnosis of myocarditis rests on well-described histopathological criteria. Appreciation for the disease-specific sensitivity of the endomyocardial biopsy, as well as the phenotypical and functional nature of inflammatory infiltrates, will enhance the clinical utility of the biopsy technique. New information regarding the role of enteroviruses in immunological sensitization and the study of enteroviruses in murine models and human patients are fostering new perspectives and routes of investigation of appropriate therapeutic interventions for myocarditis.

[Increased in vitro motility of human vascular wall myocytes from restenotic lesions of peripheral and coronary vessels]

In this study we report on the successful cultivation of human peripheral and coronary plaque specimens selectively retrieved by percutaneous Simpson atherectomy and obtained by direct operative approach. A total of 32 patients in whom plaque tissue was excised from 22 primary and 10 restenotic lesions comprise the study population. Irrespective of their origin or location, all advanced lesions showed smooth muscle cells (SMC) to be their predominant cell type proven by indirect immunofluorescence technique. Cultured endothelial cells were only identified in 2/6 surgically removed samples. Locomotion analysis of cultured smooth muscle cells was performed with a standardized computer-assisted video system. Cells of all groups exhibited random motility. However, SMC migratory velocity of restenotic origin amounted to 47.4 +/- 3.4 microns/h (n = 10, x +/- SD) and thereby was found 2.4 times (p less than 0.001) increased as compared to primary lesion values of 22.0 +/- 3.7 microns/h (n = 22, x +/- SD). This highly significant difference was seen for both peripheral and coronary lesions. Our data suggest increased SMC migratory activity to represent a basic biological mechanism involved in human accelerated arteriosclerosis and restenosis formation.

Mapping of a neutralizing antigenic site of Coxsackievirus B4 by construction of an antigen chimera

A neutralizing antigenic site of coxsackievirus B4 (CVB4) was identified by construction of an antigen chimera between coxsackievirus B3 (CVB3) and CVB4. This chimera, designated CVB3/4, was constructed by inserting five amino acids of the putative BC loop of the structural protein VP1 of CVB4 into the corresponding loop of CVB3 by site-directed mutagenesis of infectious recombinant CVB3 cDNA. The chimeric cDNA was capable of inducing an infectious cycle upon transfection of permissive host cells. The resulting chimeric virus CVB3/4 was neutralized and precipitated by CVB4 and CVB3 serotype-specific polyclonal antisera, demonstrating that it unifies antigenic properties of both coxsackievirus serotypes. In addition, the chimera elicited antibodies in rabbits which were capable of neutralizing the two coxsackievirus serotypes CVB3 and CVB4. The insertion of the CVB4-specific antigenic site into the BC loop of CVB3 reduces the efficiency of viral replication, resulting in a small-plaque morphology of the virus chimera. In summary, these data give evidence for the presence of a serotype-specific neutralizing antigenic site in the BC loop of VP1 of CVB4 (amino acids 81 to 89). Our findings suggest that the construction of intertypic chimeras can be used as a tool for the identification of antigenic sites of coxsackieviruses. The retained immunogenicity of the mapped CVB4-specific antigenic epitope, when expressed in CVB3, indicates that CVB3 can be used as a RNA virus vector for heterologous antigenic sites.

Strand-specific detection of enteroviral RNA in myocardial tissue by in situ hybridization

In this report we describe the development and application of single-stranded RNA probes for strand-specific detection of enterovirus RNA in infected heart tissue by in situ hybridization. For synthesis of RNA probes a full-length reverse-transcribed, recombinant CVB3 cDNA was inserted into the transcription vector pSPT18. Run-off transcripts of plus-strand and minus-strand orientation were produced using either T7 or SP6 RNA polymerase. Binding specificity and sensitivity of the radioactively labelled RNA probes were determined by slot-blot hybridization. Due to the high degree of genetic identity among enteroviruses, the in vitro transcribed CVB3 RNA probes hybridized with various enterovirus serotypes, including group A and B coxsackieviruses and echoviruses, which are commonly implicated in human viral heart disease. Strand-specific in situ hybridization led to detection of viral plus-strand or minus-strand RNA in infected cell cultures and in myocardial tissue sections of infected mice. In consecutive sections either viral genomic plus-strand RNA or complementary minus-strand RNA were localized in the same infected myocardial cells. In situ hybridization with enterovirus-specific and highly sensitive single-stranded RNA probes is of particular interest for the diagnosis of myocardial infections and for studies concerning viral RNA replication.

Novel ribonucleic acid species in Eimeria nieschulzi are associated with RNA-dependent RNA polymerase activity

Sporulated oocysts of Eimeria nieschulzi, E. tenella and E. acervulina were screened for the presence of putative viral nucleic acids. An RNA-dependent RNA polymerase activity in E. nieschulzi correlated with the presence of unknown nucleic acid species that were absent in the two other species of Eimeria. The novel nucleic acid species also served as templates for RNA-polymerase activity in in vitro synthesis of full-length labelled transcripts. These nucleic acid species were shown to be RNAse-sensitive and were suspected to represent the genomic RNA of a putative virus.

A search for the presence of the enteroviral capsid protein VP1 in pancreases of patients with type 1 (insulin-dependent) diabetes and pancreases and hearts of infants who died of coxsackieviral myocarditis

Using an antiserum raised to a recombinant coxsackie virus B 3 capsid protein, VP1, an immunocytochemical technique was developed which was capable of detecting the presence of all coxsackie B viruses in formalin fixed paraffin embedded infected tissue culture cells. This technique was tested on autopsy heart and pancreas from 21 patients who were thought to have died of acute coxsackievirus B myocarditis. Cardiac myocytes were positive for the VP1 protein in 12 of 20 cases where the heart was available for study. Insulitis was present in the pancreas in seven of these cases and in all seven islet endocrine cells containing VP1 were found. VP1 was only rarely found in exocrine pancreas. In heart and pancreas, cells shown to contain VP1 usually showed signs of necrosis. Autopsy pancreases from 88 patients who had died at clinical presentation of Type 1 (insulin-dependent) diabetes mellitus showed no evidence of the presence of VP1. The continuing destruction of insulin-secreting B cells seen at the time of death in the diabetic pancreas is unlikely to be due to a direct cytopathic effect of a coxsackie B virus. However, this study does not exclude the possibility that a persistent infection of B cells by a defective enterovirus may result in their destruction by an autoimmune mechanism.

Complete nucleotide sequence of infectious Coxsackievirus B3 cDNA: two initial 5' uridine residues are regained during plus-strand RNA synthesis

A full-length reverse-transcribed, infectious cDNA copy of coxsackievirus B3 (CVB3) was used to determine the nucleotide sequence of this cardiotropic enterovirus. Comparison of the nucleotide sequence and the deduced amino acid sequence of the viral precursor polyprotein with the sequences of other group B coxsackieviruses (CVB1 and CVB4) demonstrates a high degree of genetic identity. They share about 80% homology at the nucleotide level and about 90% when the amino acid sequences of the polyproteins are compared. The potential processing sites of the coxsackievirus polyproteins, as deduced from alignment with the poliovirus sequence, are conserved among these enteroviruses with the exception of the cleavage sites between VP1 and 2Apro and between polypeptides 2B and 2C. Comparison of the 5' termini of the enteroviral genomes reveals a high degree of identity, including the initial 5' consensus UUAAAACAGC, suggesting essential functions in virus replication. An important finding concerning the molecular basis of infectivity was that both recombinant CVB3 cDNA and in vitro-synthesized CVB3 RNA transcripts are infectious, although two initial 5' uridine residues found on the authentic CVB3 RNA were missing. Here, we report that cDNA-generated CVB3, as well as CVB3 generated by in vitro-synthesized RNA transcripts, regains the authentic initial 5' uridine residues during replication in transfected cells, indicating that the picornaviral primer molecule VPg-pUpU may be uridylylated in a template-independent fashion. The generation of virus or virus mutants with infectious recombinant CVB3 cDNA and in vitro-synthesized infectious CVB3 transcripts should provide a valuable means for studying the molecular basis of the pathogenicity of this cardiotropic enterovirus.

Hybridization techniques provide improved sensitivity for HCMV detection and allow quantitation of the virus in clinical samples

Hybridization techniques (slot-blot and in-situ hybridization assays) and immunostaining using murine monoclonal antibodies directed against different proteins of the human cytomegalovirus (HCMV) were compared for their sensitivity and specificity for detection of HCMV. A model system with HCMV infected human embryonic lung fibroblasts and lung biopsy specimens obtained from patients with culture positive HCMV interstitial pneumonia were used for evaluation of these techniques. The hybridization techniques were found to provide an improved sensitivity compared to immunostaining. Additionally a good correlation was found between the virus dose determined by TCID50 and the amount of viral DNA detected by slot-blot hybridization and by the number of autoradiographic silver grains per 100 cells per 2 weeks exposure time detected in the infected fibroblasts by in-situ hybridization. Thus, at least in the model system quantification of the virus was achieved by hybridization assays.

Detection of parvovirus in a patient with "reactive arthritis" by in situ hybridization

We used in situ hybridization to search for the presence of viruses in synovial fluid cell preparations obtained from patients with various forms of knee arthropathies. One patient, presenting with acute reactive arthritis, was found to replicate parvovirus DNA in cells from synovial fluid whereas six other patients with various other forms of arthritis were negative for parvovirus infection. Five patients with osteoarthritis, constituting a control group in which an infectious etiology would not be expected, were consistently negative. In addition, no hybridization was found when synovial cell preparations of all patients were hybridized in situ with DNA probes specific for Epstein-Barr virus, cytomegalovirus, or enteroviruses.

Isolated pericardial relapse following allogeneic bone marrow transplantation for acute myelogenous leukemia

A 34-year-old male patient developed an isolated pericardial relapse of an acute myelogenous leukemia (M3) 11 months after marrow grafting from his HLA-identical brother. Alloenzyme pattern analysis revealed recipient type of the myeloblasts obtained from the pericardial effusion. Recurrence of the original leukemia was preceded by a reactivation of latent cytomegalovirus (CMV) infection which, in spite of a systemic humoral immune response to the virus, persisted in the pericardium as shown by dot-blot hybridization using CMV-specific DNA fragments. Activated T cells propagated with IL-2 from the pericardial effusion did not reveal any cytotoxic or restimulation capacity on the original or relapse myeloblasts, nor on other donor, recipient or NK target cells. Local coincidence of virus persistence and leukemic relapse suggested CMV-mediated modulation of the immune response in the pericardium with consequent induction of a proliferation of the original malignant cell clone. After local chemotherapy and one course of systemic treatment the patient is still in complete remission--longer than after the marrow grafting.

[The study of intra-articular infectious agents in reactive arthritis]

Reactive arthritis is differentiated from infectious arthritis by the lack of intraarticular infectious agents. Recently 2 groups, using different techniques have demonstrated intra-articular antigens in cases of reactive arthritis associated with Chlamydia and Yersinia infections. In this article we report the preliminary results of screening cells from synovial fluid for DNA of certain microorganisms by in situ hybridization. Our findings provide complementary evidence of the intra-articular presence of at least parts of microbes.

Expression of coxsackievirus B3 capsid proteins in Escherichia coli and generation of virus-specific antisera

Subgenomic fragments of cloned infectious coxsackievirus B3 (CVB3) cDNA up to the size of the complete coding sequence of the viral polyprotein were inserted into the prokaryotic expression vector pPLc24 and expressed in Escherichia coli. Fusion proteins, containing 54 amino acids of MS2 replicase at their amino terminus followed by different parts of the CVB3 structural proteins, were expressed from several constructs. The expression product of a plasmid encoding the capsid proteins VP4, VP2, and the amino-terminal part of VP3 was obtained in high amounts. However, primary expression products containing the complete viral capsid precursor VP4-VP1 were completely degraded, indicating the presence of domains downstream from VP3 that are accessible to E. coli proteases. This finding is consistent with the observation that the structural intact expression product of the separately subcloned VP1 gene is also extremely unstable and consequently obtained only in low amounts. Two fusion proteins of non-overlapping parts of the viral structural proteins containing VP4, VP2, and VP3 or VP1, respectively, were isolated and used for the generation of antisera in rabbits. The antisera obtained recognize distinct CVB3 structural proteins in infected cell cultures as well as from purified CVB3 preparations. In addition, significant cross-reactivity of the described antisera with the corresponding structural proteins of other enteroviruses was observed, indicating that these antisera provide a valuable tool for an improved broad spectrum diagnosis of enteroviral infections.