Figure 1.
Virulence of wild-type YFV in mice is IFN-α/β-dependent while attenuation of live-attenuated 17D-204 virus is not.
Adult WT129 (solid line; open circle), G129 (solid line; open square), A129 (dotted line; closed circle), AG129 (dashed line; closed square) and STAT129 (dot-dash line; closed triangle) mice were subcutaneously inoculated in each rear footpad with 104 PFU of wild-type YFV strains, Asibi (A and D) or Angola73 (B and E) or with 17D-204 vaccine virus (C and F). Changes in weight from mock-infected counterparts were calculated daily for (A) Asibi virus-infected, (B) Angola73 virus-infected or (C) 17D-204 virus-infected mice as an indicator of morbidity. Percent survivals of (D) Asibi virus-infected, (E) Angola73 virus-infected and (F) 17D-204 virus-infected mice were calculated each day and are presented as Kaplan-Meier survival curves. Datum points are n≥4 and data are representative of at least two separate experiments.
Table 1.
Susceptibility of mice to subcutaneously inoculated Asibi and Angola73 wild-type or 17D-204 vaccine strains of yellow fever virus.
Figure 2.
Wild-type Asibi virus exhibits viscerotropism in type I IFN-deficient mice, whereas 17D-204 virus does not.
WT129 (data not shown) and A129 mice were subcutaneously inoculated with 104 PFU of Asibi (black bar) or 17D-204 (white bar) virus in each rear footpad. Viral titers in individual, perfused tissues are expressed as log10 PFU/ml of serum, PFU/draining lymph node (DLN) or PFU/g of other tissues: (A) DLN; (B) serum; (C) spleen; (D) liver; (E) bone marrow; and (F) brain. Dotted lines represent the lower limit of detection for the plaque assay. Datum points are n = 3±SD for all data sets.
Figure 3.
Cytokine levels are elevated in Asibi virus-infected A129 mice.
Serum levels of (A) IL-6 and (B) MCP-1 were measured in serum collected from mock-infected WT129 (open diamond) and A129 (closed diamond) mice, Asibi virus-infected WT129 (open circle) and A129 (closed circle) mice and 17D-204 virus-infected A129 mice (closed square) by cytokine bead array analysis (BioRad BioPlex Assay). Data are expressed as concentration of cytokine in pg/mL serum where datum points are n = 3±SD. Mock values were generated from pooled data over the course of infection.
Figure 4.
Pathologic changes were evident in liver and spleen of Asibi virus-infected A129 mice.
A129 mice were mock-infected or inoculated with 104 PFU of Asibi or 17D-204 viruses in each rear footpad. H&E-stained sections of liver and spleen are presented. Liver (A) and spleen (B) sections from mock-infected A129 animals were indistinguishable from 17D-204-infected liver (C) and spleen (D) sections, 4 d p.i. (E and F) Liver sections from Asibi virus-infected A129 mice 4 d p.i., showing diffuse inflammatory infiltrates, well-developed fatty acid steatosis involving the majority of the lobular area. Note prominent Küpffer cells (black arrows) and some accumulation of inflammatory cells in hepatic sinusoids (arrow heads). Original magnification: (E) 200×; (F) 400×. (G) Asibi virus-infected liver 6 d p.i., showing and a focus of spotty necrosis (center of field) surrounded by mononuclear inflammatory cells and higher magnification (H) showing more severe inflammatory cell infiltration surrounding portal triad and hepatocytes with intranuclear viral inclusion bodies (black arrows). Original magnification: (G) 200×; (H) 400×. (I and J) Spleen sections from Asibi virus-infected A129 mice 4 d p.i. and (K and L) 6 d p.i., showing diminishing marginal zone (MZ) and white pulp lymphoid follicles (WP), increasing number of splenic macrophages (arrow heads) and widely-distributed cells with pyknotic nuclei, morphologically consistent with apoptotic death. Original magnification: (I, K, L) 200×; (J) 400×.
Figure 5.
YFV strains Asibi and 17D exhibit differential infectivity for murine DCs and macrophages in vitro.
Cultures of primary bone marrow-derived DCs (A) and macrophages (B) generated from WT129 (circle) or A129 (triangle) mice were infected with wild-type Asibi virus (closed) or live-attenuated 17D-204 virus (open) at MOI = 0.1 PFU/cell. Viral replication was measured by plaque assay titration of progeny virions in culture supernatants. Data are expressed as log10 PFU/mL where datum points are n = 3±SD. These data were reproducible in three separate experiments.