INTRACELLULAR VIRAL LOCALIZATION IN MURINE COXSACKIEVIRUS-B3 MYOCARDITIS - ULTRASTRUCTURAL-STUDY BY ELECTRON-MICROSCOPIC IN-SITU HYBRIDIZATION

Group B Coxsackieviruses are a common cause of myocarditis. To detect the viral genome and its localization in the myocardium, we examined C 3H/He mice with Coxsackievirus B3 (CVB3) myocarditis on days 5, 8, and 14 after inoculation by the reverse transcriptase polymerase chain re action and by in situ hybridization. Sense and antisense CVB3 RNA were detected in the myocardium of all mice up to day 14 by reverse transc riptase polymerase chain reaction. Light microscopic in situ hybridiza tion with a cDNA probe for CVB3 showed clusters of positive signals in the areas of myocardial necrosis and cell infiltration. With electron microscopic in situ hybridization, CVB3 RNA was detected in the cytop lasm of cardiocytes, between the myofibrils, near the mitochondria, an d in tubular or vesicular structures. Viral RNA was also detected in n ecrotic debris, in the cytoplasm of macrophages, and in the cytoplasm of interstitial fibroblasts. These findings suggest that CVB3 RNA is r eplicated in the cytoplasm of cardiocytes, transferred into tubular or vesicular structures, released into the interstitium, and phagocytose d by macrophages. Some positive signals were also detected in the cyto plasm of cardiocytes showing close contact with infiltrating lymphocyt es, suggesting that the lymphocytes recognized virus infected cardiocy tes and caused cell-mediated immune cardiocyte damage.