Toward understanding the pathogenesis of enterovirus-induced cardiomyopathy: molecular and ultrastructural approaches.
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Publications and source records attributed to R Kandolf.
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The impact of prior exposure to a different or identical strain of Coxsackievirus B (CVB) on murine CVB myocarditis was studied using a susceptible murine host (A/J[H-2a]) and myocarditic CVB3 or avirulent CVB2 as primary or secondary infectants. The effects of secondary heterotypic infection (CVB2 followed by CVB3) and homotypic infection (CVB3 followed by CVB3) 28 days after primary inoculation, versus CVB2 or CVB3 alone, on injury and viral genomic replication, both early (day 7) and late (days 28 and 56), were evaluated. After the primary infection by CVB2, trivial viral RNA was present in the heart and other organs, and a substantial positivity was observed with CVB3 infection. Seven days after secondary heterotypic (CVB2-CVB3) infection, the quantity of CVB genome in heart, pancreas, liver, and spleen was increased compared with the virus genome in the CVB3-CVB3 group and in the group with primary CVB3 infection alone. This phenomenon was seen in the heart and spleen up to day 28 postsecondary infection. Tissue inflammation and necrosis in heart and pancreas were prominent 7 days postsecondary infection with CVB2-CVB3 and correlated well with an increased quantity of CVB genome. Virus genome was present in heart and spleen 28 days after CVB3 infection alone. Serum CVB3 neutralization titer was increased to 1:128 in CVB2-CVB3 group at days 7 and 28 postsecondary infection, and serum completely neutralized cytopathological effects of CVB3 in the CVB3-CVB3 group at day 7 and 28 postsecondary infection. Our results indicate that secondary heterotypic infection by CVB causes increased injury, inflammation, and CVB replication in target organs such as the heart and pancreas, as well as in immune compartments like the spleen. Compared with CVB3 alone, the intense inflammatory infiltriate in the CVB2-CVB3 group is as not due solely to postviral sensitization of the immune system, but rather to the inability of the host to eradicate the virus.
The research of the last decade gave new insights in the pathogenesis of viral myocarditis. The virus infection of the myocardium may be controlled by the infiltrating inflammatory cells and heal with more or less scarring. An autoimmune mediated chronic inflammation is observed as well as the persistence of virus genoms, which causes with low replication rate again chronic inflammation. The immunohistochemical characterization of the infiltrating immune cells and the molecular biological proof of virus genoms in endomyocardial specimens allow a sensitive diagnostic of the various forms of myocarditis and should guide therapy. Until now treatment trials did not differentiate between these various forms, had no control groups or very small numbers of patients. Two multicenter treatment trials in Germany referring to immunosuppressive or interferon therapy in children and adults may give--provided a better participation--recommendations for therapy.
The human parvovirus B19 (PVB19), an erythrovirus causing diverse clinical manifestations ranging from asymptomatic or mild to more severe outcomes such as hydrops fetalis, is the only known human pathogenic parvovirus so far. Although enteroviruses have long been considered the most common cause of inflammatory cardiomyopathy, PVB19 is emerging as a important candidate. Recent studies have indicated an association of PVB19 with paediatric and adult inflammatory cardiac disease. However, whether or not PVB19 has an impact on inflammatory cardiomyopathy in adult patients is still unclear. The first hints for a possible aetiopathogenetic role of the PVB19-infection and the development of cardiac dysfunction were demonstrated by molecular biology utilizing in situ hybridization (ISH) and polymerase chain reaction (PCR). According to available evidence, PVB19-associated inflammatory cardiomyopathy is characterized by infection of endothelial cells of small intracardiac arterioles and venules, which may be associated with endothelial dysfunction, impairment of myocardial microcirculation, and penetration of inflammatory cells into the myocardium.
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).
Molecular hybridization studies have demonstrated that human enteroviruses, including group B coxsackieviruses (CVB), are detectable in myocardial tissue of patients with acute and chronic myocarditis. As well, 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 discovery in various murine models of chronic myocarditis, demonstrating that coxsackievirus B3 (CVB3), typically a cytolytic virus, is capable of evading immunological surveillance in a host-dependent manner. Currently attention is focused on the analysis of molecular mechanisms of virus persistence, the characterization of viral and host factors and their impact in determining the natural course of myocardial enterovirus infections. The evidence for a causal linkage of enterovirus infection with heart muscle diseases has emerged therapeutic implications. From the view of a virologist, immunosuppressive treatment of patients revealing enterovirus infection in the myocardium with steroids is clearly contraindicated. The evaluation of potent antiviral agents, such as interferons, in established in vitro and in vivo model systems of enterovirus infection is expected to contribute significantly to new therapeutic strategies in human enteroviral heart disease.