Representative histopathology of infected macaques at day 8 p.i.. (A) Macroscopic pictures of the colon of PBj-wt virus infected macaque #6504 and PBj-Nef202/203GG virus infected macaque #267. One characteristic ulcerative-necrotic lesion is indicated by an arrow. Scale bar, 1 cm. (B) Colon tissue sections stained with hematoxylin and eosin. PBj-wt virus infected macaque #6504 showed blunting and fusion of intestinal microvilli, resulting in complete loss of tissue structure, accompanied by massive infiltration of lymphocytes into the lamina propria. Macaque #267 showed intact microvilli architecture and moderate infiltration of lymphocytes. Scale bar, 100 μm.