Pathological and virological findings of type I interferon receptor knockout mice upon experimental infection with Heartland virus

Figures

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  Fig. 1. IFNAR-/- mice were infected with 1 × 107 TCID50 of HRTV. The circles, squares, and triangles indicate the control mice, intraperitoneally (I.P.) infected mice, and subcutaneously (S.C.) infected mice, respectively. (A) Survival rate of each group of the infected mice (n = 3). (B) Sequential changes in body weight of each group of the infected mice (n = 3). Relative weights were calculated and were shown as means with standard deviations. Significance was determined using the Mann–Whitney U test. *, p<0.05; **, p<0.01; and ***, p<0.005. (C) The clinical signs of the infected mice. The above picture showed typical clinical signs of I.P. infected mice, such as ruffled fur, decline of activity, and hunched back.

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  Fig. 2. The representative pathological changes observed in the dissected IFNAR-/- mice infected with 1 × 107 TCID50 of HRTV intraperitoneally or subcutaneously or mock-infected as the control on day 3. (A) The appearance of each group of the dissected mouse was shown. The excess of peritoneal fluids and elastic stiffness reduction of gastrointestinal tracts were observed in intraperitoneally (I.P.) infected mice and subcutaneously (S.C.) infected mice. (B) The spleen of I.P infected mice., S.C. infected mice, and the control mice. The enlarged spleen was observed in I.P. infected mice. (C) The liver of I.P. infected mice, S.C. infected mice and the control mice. Patches on the surface of the liver were observed in I.P. infected mice.

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  Fig. 3. Histopathological specimens of IFNAR-/- mice infected with 1 × 107 TCID50 of HRTV intraperitoneally or subcutaneously, or mock-infected as the control. (A) Hematoxylin and eosin (HE) staining of the control mice, intraperitoneally (I.P.) infected mice, and subcutaneously (S.C.) infected mice on day 1 and day 3. The decrease of lymphocytes in the mesenteric lymph node and spleen of I.P. infected mice were observed on day 1 and day 3. * showed necrosis observed in the liver of I.P. infected mice on day 3. Scale bars, 200 μm. (B) HE staining of the liver of I.P. infected mice on day 3. * showed necrosis due to thrombosis. # showing thrombosis. Scale bars of the left and right panels showed 200 μm and 50 μm, respectively. (C-E) Immunohistochemical staining for HRTV N protein of the mesenteric lymph node (C), spleen (D), and liver (E) of I.P. infected mice and S.C. infected mice on day 1 and day 3. Scale bars, 20 μm.

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  Fig. 4. The copy numbers of HRTV RNA in the mesenteric lymph node (A), axillary lymph node (B), brain (C), lung (D), liver (E), spleen (F), kidney (G), stomach (H), intestine (I), and blood (J) of IFNAR-/- mice infected with 1 × 107 TCID50 of HRTV intraperitoneally (black bars and square dots) or subcutaneously (white bars and triangle dots) from days 1–3 (n = 3, except for blood n = 10). Bars and each dot indicated means with standard deviations and each data, respectively. The detection limits of viral RNA in the mesenteric lymph node, axillary lymph node, brain, lung, liver, spleen, kidney, stomach, intestine, and blood were 2.9 × 104 copies/g, 1.7 × 104 copies/g, 2.9 × 103 copies/g, 2.5 × 104 copies/g, 1.3 × 104 copies/g, 9.5 × 103 copies/g, 4.3 × 103 copies/g, 1.3 × 104 copies/g, 4.7 × 103 copies/g and 5.0 × 103 copies/mL, respectively, which were shown by dot lines. Significance was determined by t-test. *, p<0.05; ***, p<0.005; ****, p<0.0001; and ******, p<0.00001.

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  Fig. 5. The quantities of CXCL-1 (A), TNF-α (B), IL-12 (C), IL-1β (D), IFN-γ (E), IL-6 (F), and IL-10 (G) of IFNAR-/- mice mock-infected (gray bars and circle dots) or infected with 1 × 107 TCID50 of HRTV intraperitoneally (black bars and square dots) or subcutaneously (white bars and triangle dots) from days 1–3 (n = 10, except for intraperitoneally infected mice on day 3: n = 9). The detection limit of levels of CXCL-1, TNF-α, IL-12, IL-1β, IFN-γ, IL-6, and IL-10 were 30.1 pg/mL, 2.43 pg/mL, 44.9 pg/mL, 230 pg/mL, 13.2 pg/mL, 25.2 pg/mL, and 13.8 pg/mL, respectively, which were shown by dot lines. Significance was determined by the Mann–Whitney U test. *, p<0.05; **, p<0.01; ***, p<0.005; and ****, p<0.001.