Figure 5. NOS2^−/− mice are more susceptible to adapted-DENV-3 infection.

(A) WT and NOS2^−/− mice (n = 8 per group) were inoculated with 1LD₅₀ (100 PFU) of DENV-3 (i.p) and lethality was evaluated every 12 hours during 14 days. Results are expressed as % of survival. In (B–J), WT and NOS2^−/− mice (n = 6 per group) were inoculated with 1LD₅₀ (100 PFU) of DENV-3 (i.p) and in the seventy day of infection mice were culled and blood and tissues were collected for the following analysis: (B–D) Viral loads were recovered from the blood (B), spleen (C) and liver (D), respectively. Results are shown as the log of PFU per per mL of blood or g of tissue. (E) Serial sections from liver of WT and NOS2^−/− mice were stained with anti-DV NS3 antibody E1D8 (NS3) or an isotype control mouse IgG2a (IgG2a data not shown), and multiple sections of each tissue type were thoroughly examined for staining. Positive staining for NS3 is brown while hematoxylin counterstain is blue.Results are expressed as number of NS3-positive hepatocytes. (F) Mechanical hypernociception was assessed daily. Results are shown as the difference between the force (g) necessary to induce dorsal flexion of tibio-tarsal joint, followed by paw withdraw, before and after DENV-3 inoculation. In (G), hematocrit was shown as % volume occupied by red blood cells (left panel) and the number of platelets was shown as platelets ×10³/µl of blood (right panel). (H) Changes in Systolic blood pressure from baseline until day 5 after infection expressed as Δ of blood pressure in mmHg. In (I), AST activity determination in plasma was shown as U/dL of plasma. (J) shows semi-quantitative analysis of hepatic damage (histopathological analysis performed as modified from Paes et al, 2009) and Hematoxylin & Eosin staining of liver sections of control and WT and NOS2^−/− DENV-3-infected mice, seven days after infection. Scale Bar - 400 µm. The images presented are representative of an animal on the seventh day of infection. All results are expressed as mean ± SEM and are representative of at least two experiments. * for P<0.05 when compared to control uninfected mice. # for P<0.05 when compared to WT infected mice.1LD₅₀ corresponds to 100 PFU of adapted-DENV-3. NI- Not-infected. dpi – days post-infection. HS – hepatocyte swelling. N – necrosis. D – degeneration. H – hemorrhage. OS – Overall Score.