Fig. 3

Histopathological features of the stomach, intestinal tract, lymphatic system, and brain in the infected minks at 6 dpi compared with that in the negative-control minks. a, a’, a” Granulomatous interstitial gastritis (black arrowheads) were observed in the infected mink at 6 dpi. b, b’ Viral antigens were scattered distributed inside and outside the granulomas. c, c’ Mac-2+ macrophages were stained in the periphery of the granuloma. d, d’ Abundant MPO⁺ neutrophils were stained inside and outside the granuloma. e, e’ Massive CD3⁺ lymphocytes were stained in the periphery of the granuloma. f, f’ A few CD20⁺ lymphocytes were stained in the periphery of the granuloma. g, h The negative-control tissue was stained by hematoxylin and eosin and stained for viral S1 protein. i Viral S1 protein (red) was co-localized with Mac-2⁺ macrophages (green) (white arrowheads) in the granulomas. The major segments of the intestinal tract, including the duodenum (j), ileum (l), and rectum (n), are shown. Viral S1 protein was examined in serial sections of the duodenum (k), ileum (m), and rectum (o). p Viral S1 protein (red) was co-localized with Mac-2⁺ macrophages (green) (white arrowheads) in the lamina propria of the duodenum and a granuloma of the rectum. The major lymphatic organs include the spleen (q), tonsil (s), and hilar (u) and mesenteric (w) lymph nodes. Viral S1 protein was examined in serial sections of the spleen (r), tonsil (t), and hilar (v) and mesenteric (x) lymph nodes at 0 and 6 dpi. y The histopathological lesions in the brain including lymphocytic meningitis (black arrowhead) and perivascular inflammatory response (red arrowheads) were observed by hematoxylin and eosin staining. z Iba1 protein was visualized by immunohistochemistry. More ramified microglia (green arrowheads) were stained in the negative control, while amoeboid microglias (yellow arrowheads) were stained in the infected minks. Red scale bar at 100× = 100 µm, black scale bar at 200× = 100 µm, blue scale bar at 400× = 50 µm. Data are representative of three independent experiments. dpi days post infection