Fig. 2

Histopathological features of the cardiac, hepatic, kidney, and adrenal gland lesions in the infected minks at 6 dpi compared with the negative-control minks (n = 3/group). a The pathological changes of the whole-heart transverse section and its magnification in an infected mink at 6 dpi compared with the normal whole-heart transverse section of a negative-control mink at 0 dpi. b Compared with the normal structure of nerve fibers, more fractured and entangled nerve fibers (white arrowhead) were stained by silver staining. c More viral S1 antigen was distributed in the myocardium of infected minks than control minks. d Mac-2⁺ macrophages were scattered in the interstitium of the fractured myocardium compared with that in the negative control. Viral S1 protein (red) was co-localized with Mac-2⁺ macrophages (green) in the lesion area of the heart tissues stained by immunofluorescence. Vascular endothelial cells are stained with CD31 (magenta). e Abundant CD3⁺ lymphocytes were stained in the serial section from the lesion area in the myocardium of infected minks compared with the negative controls. f A few CD20⁺ lymphocytes were stained in the serial section from the lesion area in the myocardium of infected minks compared with the negative controls. g Massive MPO⁺ neutrophils were stained in the serial section from the lesion area in the myocardium of infected minks compared with the negative controls. h Compared with normal control livers, affected livers had focal to multifocal infiltration, multinuclear syncytial hepatocytes (red arrowheads), and proliferation of bile ducts. i More viral S1 antigen was distributed in the hepatic sinusoids and in the areas of inflammatory infiltration around the bile ducts of the infected minks compared to controls. j Mac-2⁺ macrophages were scattered in the hepatic sinusoids in the serial section. k Massive CD3⁺ lymphocytes were stained in the serial section from the infected minks compared with the negative controls. l Abundant CD20⁺ lymphocytes were stained in the serial section from the infected minks compared with the negative controls. m More MPO⁺ neutrophils were stained in the serial section from the infected minks compared with the negative controls. n Viral S1 protein (red) was co-localized with Mac-2⁺ macrophages (green) (white arrowheads) in the hepatic sinusoids stained by CD31 (magenta), while no viral S1 protein was in the negative control. o Compared with the normal control kidneys, affected kidneys exhibited interstitial nephritis and contracted glomeruli with expansive Bowman’s capsules. p More viral S1 antigen was distributed in the renal tubules and infiltrate of infected minks compared to normal controls. q Massive CD3⁺ lymphocytes were stained in the serial section from the infected minks compared with the negative controls. r Abundant CD20⁺ lymphocytes were stained in the serial section from the infected minks compared with the negative controls. s More MPO⁺ neutrophils were stained in the serial section from the infected minks compared with the negative controls. t Viral S1 protein (red) was co-localized with infiltrating Mac-2⁺ macrophages (green) (white arrowheads), while no viral S1 protein was in the negative control. u Compared with the normal control adrenal gland, the affected tissues exhibited inflammatory cell infiltration. v More viral S1 antigen was distributed in the cortical cells and the chromaffin cells of infected minks than normal controls. Red scale bar at 100× = 100 µm, black scale bar at 200× = 100 µm, blue scale bar at 400× = 50 µm, white scale bar at 400×=100 µm. Data are representative of three independent experiments. dpi days post infection