Myocarditis severity is attenuated in mice infected with the infectious clone-derived virus, pBRCVB3.

<p><b>Histology.</b> A/J mice were infected with Wt virus or the virus derived from pBRCVB3 i.p., and hearts and pancreata were harvested at termination on day 21 postinfection or as the animals died or euthanized. The tissues were examined by H and E staining. Representative sections from three individual animals infected with Wt virus or pBRCVB3 virus are shown (n = 15 to 17 mice per group), whereas the sections obtained from uninfected animals were used as controls. (<b>A) Hearts.</b><u>Top panel (control group)</u>: heart section from uninfected animal without inflammation, mineralization or necrosis; <u>middle panels (Wt virus-infected):</u> extensive infiltrates of macrophages and lymphocytes into the myocardium filling areas of myocardial cell loss/necrosis (Mouse 1), extensive large foci of necrosis and mineralization surrounded by inflammation consisting of macrophages and lymphocytes (Mouse 2), multiple small foci of necrosis and mineralization infiltrated by a few inflammatory cells (Mouse 3); <u>bottom panels (pBRCVB3 virus-infected)</u>: small focal inflammatory infiltrates into myocardium (Mouse 1), a small foci of necrosis in the myocardium (Mouse 2), small foci of lymphocytic inflammation (Mouse 3). (<b>B) Pancreata.</b><u>Top panel (control group):</u> pancreas from an uninfected animal showing intact islets; <u>middle panels (Wt virus-infected)</u>: diffuse atrophy with scattered lymphocyte infiltrates (Mouse 1), acute necrosis, mineralization and inflammation (Mouse 2), diffuse marked atrophy with mild diffuse inflammation (Mouse 3); <u>bottom panels (pBRCVB3 virus-infected)</u>: diffuse atrophy and lymphocytic infiltrates (Mouse 1), diffuse necrosis with pyknotic nuclei (Mouse 2), diffuse atrophy with mild inflammation (Mouse 3). Arrows indicate the lesions (N, necrosis; M, mineralization; and I, inflammation). Original magnification: 10x (hearts) and 40x (pancreata). (<b>C) Viral titers.</b> Hearts and pancreata obtained from the above groups on days 5, 7 and 10 postinfection were processed for determining the viral titers as described in the ‘methods’ section and the titers were compared between groups. Left panel, hearts; right panel, pancreata.