Initial weight and virus dose: two factors affecting the onset of acute coxsackievirus B3 myocarditis in C57BL/6 mouse—a histopathology-based study

Abstract

C57BL/6 mice have been considered resistant to cardiotropic coxsackievirus B3 (CVB3)-induced myocarditis. However, establishment of viral myocarditis model in C57BL/6 mouse is still a necessity. Here, we discuss the effects of mouse initial body weight and different virus inoculation doses on the onset of acute viral myocarditis in C57BL/6 mouse. According to initial body weight, mice were grouped into group A (3-4 weeks, 11-15 g) and group B (5-6 weeks, 18-20 g). Then, each group was divided into three subgroups inoculated with different virus doses: 1000 50% tissue culture infectious dose (TCID(50))/ml, 10,000 TCID(50)/ml, and 100,000 TCID(50)/ml. Virus existence and myocardium inflammatory infiltration conditions were observed and evaluated 7 days postinfection. Immunohistochemistry staining showed that virus capsid protein VP1 appeared in the myocardia of virus-infected mice. Three subgroups in the lower-body-weight group (group A) came out with a higher mortality (40%-100%), while the higher-body-weight group (group B) showed a tendency for body weight decline. Histopathologically, myocardia of the survival cases in the lower-initial-body-weight group got inflammatory infiltration, while almost no inflammation appeared in the dead cases. In the higher-body-weight group, myocardium inflammatory infiltration deteriorated with the increase of virus doses and bared a relatively sound survival rate. This study indicated that the initial body weight and virus infection dose are two factors affecting the onset of viral myocarditis in C57BL/6 mice. Accordingly, initial body weight of 18-20 g and an inoculation dose of 100,000 TCID(50)/ml × 0.3 ml CVB3 might be an optimal choice to induce acute viral myocarditis in C57BL/6 mice.