CCR5 and nervous system disorder: Although both Ccr5+/+ and Ccr5−/− mice infected with JEV exhibited neurological disorders at 4–5 dpi, which is before functional adaptive immune responses were fully induced, we examined the generation of JEV-specific CD4+ T cell responses in surviving Ccr5+/+ and Ccr5−/− mice at 7 dpi using intracellular CD154 staining combined with intracellular cytokine IFN-γ staining, because CD154+CD4+ T cells could enable us to enumerate viable JEV-specific CD4+ T cells in response to stimulation with epitope peptides [28, 29].