Susceptibility to Myocarditis Is Dependent on the Response of αβ T Lymphocytes to Coxsackieviral Infection

Abstract

Abstract —Viral myocarditis is an important cause of heart failure and dilated cardiomyopathy. T lymphocytes are implicated in myocardial damage in murine models of coxsackievirus B3 (CVB3) myocarditis. We used knockout mice lacking CD4 (CD4 −/− ), CD8 (CD8 −/− ), both coreceptors (CD4 −/− CD8 −/− ), or the T-cell receptor β chain (TCRβ −/− ) to address the contribution of T-cell subpopulations to host susceptibility to CVB3 myocarditis. Severity of disease was magnified in CD8 −/− mice but attenuated in CD4 −/− mice, consistent with a pathogenic role for CD4 + lymphocytes. Elimination of both CD4 and CD8 molecules from T lymphocytes by genetic knockout better protected mice from myocarditis, demonstrating that both CD4 + and CD8 + T cells contribute to host susceptibility. The same benefit occurred in TCRβ −/− mice, with prolonged survival and minimal myocardial disease observed after CVB3 infection. Elevated interferon-γ and decreased tumor necrosis factor-α expression are associated with attenuated myocardial damage in CD4 −/− CD8 −/− mice. These results show that the presence of TCRαβ + T cells enhances host susceptibility to myocarditis. The severity of myocardial damage and associated mortality are dependent on the predominant T-cell type available to respond to CVB3 infection. One mechanism by which CD4 + and CD8 + T-cell subsets influence the pathogenesis of myocarditis may involve specific cytokine expression patterns.