Myocardial changes after infection with Coxsackie virus B3 in nude mice

Athymic BALB/c-nu/nu (nu/nu) mice were inoculated i.p. with Coxsackie virus B3. The infected nu/nu mice were studied histopathologically, virologically and serologically in comparison with BALB/c-nu/+ (nu/+), BALB/c-+/+(+/+) and conventional ddY/S mice inoculated with the same virus. The virus titre in the hearts of nu/nu mice was roughly similar to that of nu/+ or +/+ and was higher than that of ddY/S. The neutralizing antibody titre in nu/nu mice was slightly lower than that of nu/+ or +/+ mice and somewhat lower than that of ddY/S mice. Histopathologically, there was a lack of mononuclear cells in myocarditis produced by Coxsackie virus B3 in athymic nu/nu mice. In contrast, myocarditis with mononuclear cell infiltrations were found in nu/+, +/+ and ddY/S mice. The lack of mononuclear cell reaction was a distinguishing difference in the myocardial changes of athymic nu/nu mice from those in nu/+, +/+ and ddY/S mice. The incidence in the myocardial lesions of nu/nu mice was about the same as those in nu/+, +/+ and ddY/S mice. However, the intensity of the myocardial changes of nu/nu mice was significantly less than that of other three groups. From the histopathological viewpoint, it is suggested that inflammatory response in the myocardium of mice infected with Coxsackie virus B3 is thymus-dependent.