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Figure 1. Representative photomicrographs of histologic changes
and immunohistochemical staining of tissues from ground squirrels infected
with monkeypox virus. A) Liver from a ground squirrel (intranasal infection)
showing mild degenerative changes, including early steatosis, and purple-colored
viral cytoplasmic inclusion bodies in the hepatocytes (40x objective).
B) Spleen from a ground squirrel infected intraperitoneally, showing extensive
necrosis (20x objective). C) Liver showing positive antigen staining of
the intrahepatocytic inclusion bodies; antigen is present in the cytoplasm
and to a lesser extent in cell membranes (40x objective). D) Spleen from
a ground squirrel infected intraperitoneally, showing positive antigen
staining in the interstitial cells, endothelial cells (arrowheads), and
the surface mesothelial cells (arrows) (20x objective). E) Same tissue
sample as D, showing the edge of the spleen with antigen-positive mesothelial
layer; the adjacent fat and fibrous tissue show necrosis but are also
strongly positive for antigen (20x objective). F) Lung from the same animal
showing many antigen-positive interstitial cells and pneumocytes (40x
objective). A and B, hematoxylin and eosin stain; C–F, immunoperoxidase
stain.
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