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J. Virol., Nov 1995, 6720-6728, Vol 69, No. 11
A Henke, S Huber, A Stelzner and JL Whitton
Coxsackievirus infections have previously been shown to cause acute or
chronic myocarditis in humans, and several mouse models have been
established to study the pathology of this disease. Myocardial injury may
result from direct viral effects and/or may be immune mediated. To
determine the relative roles of these processes in pathogenesis, we have
compared coxsackievirus B3 (CVB3) infections of normal and immuno-
compromised transgenic knockout (ko) mice. CVB3 was able to infect all
strains used (C57BL/6, CD4ko, and beta-microglobulin ko [beta 2Mko]), and
following intraperitoneal injection, two disease processes could be
distinguished. First, the virus caused early (3 to 7 days postinfection)
death in a viral dose-dependent manner. Immunocompetent C57BL/6 mice were
highly susceptible (50% lethal dose = 70 PFU), while immunodeficient
transgenic ko mice were less susceptible, showing 10- and 180-fold
increases in the 50% lethal dose (for CD4ko and beta 2Mko mice,
respectively). Second, a histologic examination of surviving CD4ko mice at
7 days postinfection revealed severe myocarditis; the inflammatory
infiltrate comprised 40 to 50% macrophages, 30 to 40% NK cells, and 10 to
20% CD8+ T lymphocytes. The infiltration resolved over the following 2 to 3
weeks, with resultant myocardial fibrosis. In vivo depletion of CD8+ T
lymphocytes from these CD4ko mice led to a marked reduction in myocarditis
and an increase in myocardial virus titers. beta 2Mko mice, which lack
antiviral CD8+ T cells, are much less susceptible to early death and to the
development of myocarditis. We conclude that our data support a strong
immunopathologic component in CVB3-induced disease and implicate both CD4+
and CD8+ T cells. Compared with immunocompetent animals, (i) mice lacking
CD4+ T cells (CD4ko) were more resistant to virus challenge, and (ii) mice
lacking CD8+ T cells (beta 2Mko and in vivo-depleted CD4ko) showed enhanced
survival and a reduced incidence of the later myocarditis. Nevertheless,
the picture is complex, since (iii) removal of the CD4+ component, while
protecting against early death, greatly magnified the severity of
myocarditis, and (iv) removal of the CD8+ cells from CD4ko mice, although
protecting against early death and later myocarditis, led to markedly
increased virus titers in the heart. These data underscore the complex
balance between the costs and benefits of effective antiviral immune
responses.
Copyright © 1995, American Society for Microbiology
The role of CD8+ T lymphocytes in coxsackievirus B3-induced myocarditis
Department of Neuropharmacology, Scripps Research Institute, La Jolla, California 92037, USA.
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