Figure 4. IFN-γ controls NOS2-mediated NO production during adapted-DENV-3 infection.

(A–C) WT mice (n = 6 mice per group) were inoculated with 10LD₅₀ (1000 PFU) of adapted-DENV-3 (i.p) and 3, 5 or 7 days after infection, mice were culled and tissue were collected for the following analysis: (A) Determination of NOS2 RNA expression by qPCR in spleen of control and DENV-3 infected mice. Results are shown as fold increase over basal expression in naive mice. (B) Determination of NOS2 staining by immunohistochemistry in liver sections of control and DENV-3 infected mice. Results are expressed as number of positive cells per mm² of liver. (C) Esplenocytes were incubated with DAF-2DA and fluorescence determined. Results are expressed as fold increase in fluorescence over stained cells of naive mice. (D–E), WT and IFN-γ^−/− mice (n = 6 per group) were inoculated with 1LD₅₀ (100 PFU) of DENV-3 (i.p) and in the fifth day of infection mice were culled and tissues were collected for the following analysis: (D) Determination of NOS2 RNA expression by qPCR in spleen of WT and IFN-γ^−/− DENV-3 infected mice. Results are shown as fold increase over basal expression in naive mice. (E) Determination of NOS2 staining by immunohistochemistry in liver sections of WT and IFN-γ^−/− DENV-3 infected mice. Results are expressed as number of positive cells per mm² of liver. Results are expressed as mean ± SEM and are representative of at least two experiments. * for P<0.05 when compared to control naive mice. # for P<0.05 when compared to WT infected mice. 10LD₅₀ corresponds to 1000 PFU of DENV-3. 1LD₅₀ corresponds to 100 PFU of DENV-3. dpi – days post-infection. NI – Not-infected.