Coxsackievirus-induced myocarditis in mice: a model of autoimmune disease for studying immunotoxicity

Abstract

Excellent animal models are available for virus-induced and autoimmune heart disease that are remarkably similar to human disease. Developing good animal models for heart disease is crucial because cardiovascular disease is now the leading cause of death in the United States and is estimated to be the leading cause of death in the world by the year 2020. A significant proportion of heart disease in Western populations is associated with inflammation. Myocarditis, or inflammation of the heart muscle, is the major cause of sudden death in young adults. Although most individuals recover from acute myocarditis, genetically susceptible individuals may go on to develop chronic myocarditis and dilated cardiomyopathy (DCM) resulting in congestive heart failure. In this article, we describe a model of autoimmune myocarditis and DCM induced by inoculation with heart-passaged coxsackievirus B3 (CVB3). Intraperitoneal inoculation of susceptible mice with CVB3 induces acute cardiac inflammation from days 7 to 14 postinfection (pi) that progresses to chronic myocarditis and DCM from day 28 to at least 56 pi. The model of CVB3-induced myocarditis presented here allows dissection of the contribution of viral infection and xenobiotics on immune dysregulation and inflammation in the heart. An improved understanding of the interaction between environmental exposures and the development of heart disease represents a clear challenge for immunotoxicologists.

Figure 1

Progression to chronic autoimmune myocarditis following CVB3 infection of susceptible BALB/c mice. Intraperitoneal inoculation of BALB/c (A) or C57BL/6 (B) mice with a heart-passaged stock of CVB3 (Nancy strain) induces inflammation in the heart from day 7 to 21 after infection (acute myocarditis). During acute myocarditis, infectious virus can be detected in the heart of both mouse strains but does not correlate with the percent inflammation. Susceptible strains of mice (i.e. BALB/c) progress to a chronic phase of disease from day 35 to at least day 56 characterized by large areas of fibrosis, necrosis, pericarditis and DCM. The progression of myocarditis in female BALB/c and C57BL/6 mice is shown.

Figure 2

Male mice develop significantly increased inflammation in the heart during acute myocarditis. BALB/c mice were infected with CVB3 on day 0 and CD45⁺ immune cells isolated from the heart and analyzed by FACS on day 8 pi. Males have increased numbers of CD45⁺ immune cells in the heart compared to females (A). The infiltrate is composed of (B) macrophages (F4/80), macrophages and neutrophils (CD11b), CD4⁺ helper T cells, CD8⁺ cytolytic T cells, B cells (B220), mast cells (CD117), natural killer (NK) cells, and dendritic cells (CD11c).

Figure 3

Chronic, autoimmune myocarditis following CVB3 infection is characterized by fibrosis, pericarditis and DCM. BALB/c mice were infected with CVB3 on day 0 and the heart examined at day 35 pi for fibrosis (collagen deposition stains bright blue) (A), pericarditis (B) and DCM (D). DCM is not present during acute myocarditis (at day 12 pi) (C). Original magnificantion, x64 (A and B) and x2.5 (C and D).