Secondary enterovirus infection in the murine model of myocarditis. Pathologic and immunologic aspects.

Enteroviruses are implicated as etiologic agents in the inflammatory diseases myocarditis and polymyositis. In this report, we show that a previous enterovirus exposure in mice can influence development of myocardial inflammation with a second enteroviral exposure. Inoculation of 25-day-old male C3H/HeJ mice with 10(3) or 10(5) plaque-forming units (PFU) of infectious or ultra violet (UV)-inactivated coxsackievirus B2 (CVB2), followed by inoculation 28 days later with 10(5) PFU of a myocarditic variant of coxsackievirus B3 (CVB3-m) results in more intense myocardial inflammation and injury than is seen in age-matched mice inoculated with CVB3-m alone. More severe disease occurs with the lower primary dose of CVB2. Neutralizing antibody to CVB2 is detected early after primary inoculation and neutralizing antibody to CVB3 is first detected 5 days after secondary inoculation. In vitro proliferation of splenocytes from mice inoculated with one or both viruses occurs in response to both CVB2 and CVB3 antigens. We recently demonstrated that murine T cells are capable of recognizing an enterovirus group antigen. Thus cell-mediated immune responses to a conserved antigenic epitope(s) among the enteroviruses may be involved in the exacerbation of myocardial inflammatory disease during a second enterovirus infection. The secondary infection model described here may more accurately mirror virus-induced myocarditis in the human population because the majority of adults have been exposed to several enteroviruses before induction of disease.