Experimental myocarditis by adenoviruses. I. Electron microscopy and infectivity of Aura virus in the mouse heart.

The Aura virus myocarditis of the new-born mouse was studied by virus assay and electron microscopy. High titers of virus were found in heart and blood from intracerebrally and subcutaneously infected mice, at times when virus particles and lesions were more frequently detected by electron microscopy (on the third postinoculation day). The cardiac myocyte of the Aura virus-infected mouse showed virus precursors within the cytoplasm and budding particles from the plasma membranes and from walls of sarcotubules. Mature virus particles were found in the intercellular space, within the lumina of sarcotubules and in membrane-bound intracellular spaces. Cell-free viral aggregates were observed within the lumina of myocardial capillaries. Incipient pathologic changes of the myocyte (swelling of mitochondria, sarcotubules and cytoplasmic matrix, and margination of chromatin in the nucleus) were relatively frequent findings. On the other hand, advanced lesions (loss of periodic bands of myofibrils, disorderly disposition of myofilaments, necrotic myocytes) were found in scarce, small foci.