Histopathology of the lung following 1.25×10⁴<i>Orientia</i> challenge.

<p>H & E stained uninfected lung tissue (<b>A-20×</b>) and IHC of uninfected lung (<b>B-40×</b>) compared with lung from i.p. inoculated mice 12 dpi (H&E <b>C-20×</b>, IHC <b>D-40×</b>), and lung from i.v. inoculated 15 dpi (H&E <b>E-20×</b>, IHC <b>F-40×</b>). All i.p. infections were lethal with less severe pulmonary cellular infiltrate when compared to that of i.v. infected mice with capillary endothelial cell infection of the aveolar septa.</p

Histopathology of the liver and kidney following lethal intravenous <i>Orientia</i> challenge at days 9 and 12 pi.

<p>Portal triaditis (<b>A-arrow; 20×</b>) was prominent at 9 dpi, and at 12 dpi perivascular infiltrates were observed in the hepatic sinusoids (<b>B-arrow; 20×</b>). Mild perivascular infiltrates were observed in the kidney at 9 dpi (<b>C-20×</b>), and at 12 dpi (<b>D-arrow; 20×</b>) cellular infiltrates were observed throughout the kidney, particularly as peritubular infiltrates.</p

Histopathology of mice following lethal intravenous <i>Orientia</i> challenge at days 9 and 12 pi.

<p>Immunohistochemical staining of tissues from animals 9 and 12(<b>A-20×</b>) was observed in the majority of animals on 9 dpi with cerebral perivascular, lymphohistiocytic infiltrates (<b>B-inset; 40×, C-100×</b>), cerebral hemorrhage (<b>D-100×</b>), and endothelial infection (<b>E-100×</b>) in moribund animals at 11 dpi. Pulmonary cellular infiltrates were marked 9 dpi resulting in interstitial pneumonia (<b>F-20×</b>). At 12 dpi (<b>G-20×</b>), peribronchial and perivascular cellular infiltration, interstitial pneumonia, and edema (<b>G-arrow</b>) were observed in all animals.</p

Bacterial load (47 kDa gene copies/pg of DNA or µL of blood) kinetics of 1.25×10⁶ FFU challenged C57BL/6 mice.

a<p>, ND- not detected.</p

Bacterial load (47 kDa gene copies/pg of DNA or µL of blood) kinetics of 1.25×10⁴ FFU challenged C57BL/6 mice.

a<p>, ND- not detected.</p><p>*, only two animals remained.</p

Summary of disease manifestations.

<p>*, mice began exhibiting hunched posture, lethargy, ruffled fur, and rapid breathing.</p><p>**, Animals had accumulation of turbid, peritoneal exudate.</p><p>***, Animals had accumulation of ascites fluid.</p><p>, Hepatosplenomegaly was less severe than i.v. inoculated animals.</p

Histopathological changes in livers of mice infected with the rSA51, wt Entebbe, or wt OS7 strains of Rift Valley fever phlebovirus (RVFV) at 2 days post infection (dpi).

<p>Mice intraperitoneally infected with 1x10³ PFU of rSA51 (A–C), wt Entebbe clone 4 (D–F), or wt OS7 (G–I) were euthanized at 2 dpi. A mouse intraperitoneally mock-infected with PBS (J–L) was used as a control. Liver tissues, which were fixed with 10% neutral buffered formalin and embedded in paraffin blocks, were used for histopathological examinations. Thin sections were stained with hematoxylin-eosin staining (A, D, G, and J). Corresponding lesions were also incubated with anti-RVFV N rabbit polyclonal antibody to analyze immunohistochemistry (IHC; B, E, H, and K). Specific signals (red) derived from Vector Red Alkaline Phosphatase substrate were detected via the streptavidin-biotin method using the UltraVision Alk-Phos kit. Quantification of the area of positive signals normalized to the tissue area in each IHC image was performed via FIJI Image J software after color deconvolution (C, F, I, and L). Arrowheads (A, D, and G) indicate Councilman bodies, and inset images (A, D, and G) show hepatocytes with filamentous eosinophilic intranuclear inclusion bodies (arrows). C = central vein; P = portal vein. Bars represent 50 μm.</p

Passage histories of wild-type RVFV strain stocks.

<p>Passage histories of wild-type RVFV strain stocks.</p

Replication kinetics of recombinant South Africa 1951 (rSA51) and Zinga (rZinga) strains in culture cells.

<p>(A–B) Replication kinetics of recombinant ZH501 (rZH501), rSA51, and rZinga strains or wt ZH501 or wt SA51 strains in human lung diploid MRC-5 cells (A) or sheep kidney OA4.K/S1 cells (B). Cells were infected with RVFV at MOI 0.01. Infectious virus titers (plaque-forming units, PFU) were determined by plaque assay.</p

Histopathological changes of spleens in mice infected with rSA51, wt Entebbe, or wt OS7 strains of Rift Valley fever phlebovirus (RVFV) at 2 days post infection (dpi).

<p>Mice intraperitoneally infected with 1x10³ PFU of rSA51 (A–C), wt Entebbe (D–F), or wt OS7 (G–I) were euthanized at 2 dpi. A mouse intraperitoneally mock-infected with PBS (J–L) was used as a control. Spleen sections were stained with hematoxylin-eosin staining (A, D, G, and J). Corresponding lesions were also incubated with anti-RVFV N rabbit polyclonal antibody to analyze immunohistochemistry (IHC; B, E, H, and K). Quantification of the area of positive signals normalized to the tissue area in each IHC image is also shown (C, F, I, and L). Arrowheads (A) indicate necrotic area in the marginal zone. Rp = red pulp; Fo = follicle; Mz = marginal zone. Bars represent 50 μm.</p