Persistence of viral genome into late stages of murine myocarditis detected by polymerase chain reaction

This study involves the determination of the relationship between viral replication and development of cardiomyopathy by evaluating the persistence of viral genome during acute and chronic stages of murine myocarditis. This was carried by using Northern blot hybridization and polymerase chain reaction (PCR). DBA/2 mice (n = 146) were injected peritoneally with 10 plaque-forming units (PFU) of encephalomyocarditis (EMC) virus, and randomly sacrificed at 4, 7, 10, 14, 21, 28, 35 and 42 days following infection. Histology revealed typical lesions of acute viral myocarditis followed by dilated cardiomyopathy. Northern blot analysis showed detectable viral RNA in the infected hearts initially at day 4, peaking by day 7, diminishing between day 7 and day 14, and absent at day 21 and day 28. However, residual viral target signals were consistently detectable into late stages of cardiomyopathy on day 21, 28, 35 and 42 by PCR. Therefore, PCR is an extremely sensitive method for detecting residual viral genome and viral persistence in the myocardium, and may offer new insights into the pathogenesis of chronic myocarditis leading to dilated cardiomyopathy.