Differing cardiotropic and myocarditic properties of group B type 4 coxsackievirus strains

Morphologic and phenotypic characteristics of myocarditis in two pigs infected by foot-and mouth disease virus strains of serotypes O or A

Myocarditis is often cited as the cause of fatalities associated with foot-and-mouth disease virus (FMDV) infection. However, the pathogenesis of FMDV-associated myocarditis has not been described in detail. The current report describes substantial quantities of FMDV in association with a marked mononuclear inflammatory reaction, interstitial edema and cardiomyocyte degeneration in the myocardium of two pigs that died during acute infection with either of two different strains of FMDV. Despite similar clinical progression, there was a marked variation in morphological characteristics of myocarditis with a significant difference in intensity of myocardial inflammation between the two cases. Phenotypic characterization of leukocyte populations revealed that in both cases, the inflammatory infiltrate consisted mainly of combinations of CD172a+, CD163+ and CD44+ cells, with a distinct subset of CD8+ cells, but with consistent lack of detection of CD3+ and CD21+ cells. This suggests that the FMDV-associated acute myocardial inflammation in the two observed cases consisted mainly of leukocytes of monocyte lineage, with a distinct population of CD8+ cells which, based on lack of CD3 detection in serial sections, are likely to represent NK cells.

Coxsackievirus myocarditis: interplay between virus and host in the pathogenesis of heart disease

Coxsackievirus (CVB) infection is a significant cause of myocarditis and dilated cardiomyopathy (DCM). Heart disease may be caused by direct cytopathic effects of the virus, a pathologic immune response to persistent virus, or autoimmunity triggered by the viral infection. CVB interacts with its host at multiple stages during disease development. Signaling through viral receptors may alter the intracellular environment in addition to facilitating virus entry. Viral genetic determinants that encode cardiovirulence have been mapped and may change depending on the nutritional status of the host. Virus persistence is directly associated with pathology, and recent work demonstrates that CVB evolves into a slowly replicating form capable of establishing a low-grade infection in the heart. The innate immune response to CVB has taken on increasing importance because of its role in shaping the development of the adaptive immune response that is responsible for cardiac pathology. Studies of T cell responsiveness and the development of autoimmunity at the molecular level are beginning to clarify the mechanisms through which CVB infection causes inflammatory heart disease.

Coxsackie virus B4 infection of the mouse pancreas: I. Detection of virus-specific RNA in the pancreas by in situ hybridisation

The pathology of Coxsackie virus B4 (CVB4) infection in a murine model was investigated by in situ hybridisation using a biotinylated cDNA probe derived from CVB4. During the acute phase of infection virus RNA sequences were detected in the exocrine pancreas of 60% of mice infected with a pancreotropic variant of CVB4. A positive hybridisation signal was observed in other organs in some animals including the heart and liver of 1 mouse 28 days after infection. The cellular distribution of virus RNA sequences corresponded well with the histological findings in most tissues. Possible causes for failure of hybridisation in some infected pancreases are discussed in conjunction with potential application of the technique in human pancreas biopsy samples.

Derivation and characterization of an efficiently myocarditic reovirus variant

A reovirus variant, 8B, was isolated from a neonatal mouse which had been inoculated with a mixture of two reovirus strains: type 1 Lang (T1L) and type 3 Dearing (T3D) (E. A. Wenske, S.J. Chanock, L. Krata, and B. N. Fields, J. Virol. 56:613-616, 1985). 8B is a reassortant containing eight gene segments derived from the T1L parent and two gene segments derived from the T3D parent. Upon infection of neonatal mice, 8B produced a generalized infection characteristic of many reoviruses, but it also efficiently induced numerous macroscopic external cardiac lesions, unlike either of its parents. Microscopic examination of hearts from infected mice revealed myocarditis with necrotic myocytes and both polymorphonuclear and mononuclear cellular infiltration. Electron microscopy revealed viral arrays in necrotic myocytes and dystrophic calcification accompanying late lesions. Determination of viral titers in hearts from T1L-, T3D-, or 8B-infected mice indicated that growth was not the primary determinant of myocardial necrosis. Results from inoculations of athymic mice demonstrated that T cells were not a requirement for the 8B-induced myocarditis. Finally, 8B was more cytopathic than either of the parent viruses in cultured mouse L cells. Together, the data suggest that 8B-induced myocardial necrosis is due to a direct effect of reovirus on myocytes. Reovirus thus provides a useful model for the study of viral myocarditis.

Analysis of virus protein heterogeneity among group B coxsackie viruses using a "mini" two-dimensional gel electrophoresis system

The application of a small format two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) system to the study of protein heterogeneity among group B coxsackie virus (CVB) isolates is described. Under the conditions of electrophoresis developed during this study, protein samples could be processed within 7 h and up to 300 intracellular proteins were resolved from uninfected HEp-2 cell lysates. 2D-PAGE was used to characterise the intracellular proteins of clinical CVB isolates of serotypes 4 and 5. Intracellular proteins from virus-infected cells were radiolabelled using a pulse-chase protocol under conditions which promoted inhibition of cellular protein synthesis. Depending on the CVB serotype up to 11 intracellular virus proteins were identified, ranging in molecular weight between 14,000 and 54,000. Although the overall two-dimensional protein profiles were characteristic for the two CVB serotypes, within a CVB serotype there was some heterogeneity of the virus proteins, mainly affecting the proteins' net charge. The sensitivity of 2D-PAGE in detecting subtle differences in virus proteins combined with the convenience of the small gel format makes this a suitable approach for the study of the molecular epidemiology of human virus pathogens.

Pathogenesis of acute myocardial necrosis in inbred mice infected with coxsackievirus B3

The pathogenesis of myocardial necrosis due to CB3W infection was studied in BALB/c and C3H/HeJ mice. BALB/c mice infected with 5 x 10(4) pfu were found to die of massive hepatic coagulative necrosis before myocardial changes occurred. Reducing the inoculum size to 5 x 10(2) pfu resulted in sublethal hepatic involvement and multifocal myocardial coagulative necrosis by day 7 p.i. In contrast, C3H/HeJ mice survived infection and developed multifocal myocardial coagulative necrosis, but not liver disease following inoculation with as much as 5 x 10(6) pfu of CB3W. As with BALB/c mice infected with 5 x 10(2) pfu, myocardial lesions became apparent in C3H/HeJ mice a few days after peak cardiac virus titer was attained. Minimal inflammatory infiltrate was seen following development of cellular necrosis and was restricted to the areas of virus-induced pathologic change. However, no evidence was found for virus-specific cytotoxic T cell activity or for delayed type hypersensitivity responses. Furthermore, myocardial necrosis in CB3W-infected, T cell-depleted C3H/HeJ mice was as severe as in CB3W-infected, immunocompetent mice. These data have led us to conclude that cardiac lesions were due to virus-induced cytopathology rather than immunopathogenic mechanisms.

Neutralization epitope diversity of coxsackievirus B4 isolates detected by monoclonal antibodies

Only recently have we begun to fully realize the diversity of virions within a single human isolate of the group B Coxsackieviruses. These intratypic (strain) differences may be one of the important factors influencing pathogenesis, e.g., myocarditis vs. pancreatitis. Yet, until the virion strains within a type can be well differentiated, a thorough analysis of the pathogenic potential of each is not possible. We compared two human isolates, JVB and Edwards, and 15 isolates derived from these two in search of determinants of strain specificity and to evaluate the diversity/stability of neutralization epitopes on the virions comprising each isolate. Polyclonal antisera failed to show strain specific determinants. However, monoclonal antibodies directed to individual neutralization epitopes defined strain specific differences. Plaque reduction neutralization tests with these monoclonal antibodies allowed the quantitation of the expression of epitopes on the virions in each isolate. These data helped to establish the limits of diversity and stability of the neutralization epitopes of Coxsackievirus B4 virions and describe the changes in epitopes among laboratory isolates.