CD4 and encephalitis: Unlike earlier works on flavivirus encephalitis [16, 17], the present study showed that the JEV burden in the extraneural tissue and CNS of Ccr5+/+ mice was similar to that in Ccr5−/− mice, with transiently and early increased CNS infiltration of NK and CD4+ cells, but not CD8+ T cells, in Ccr5+/+ mice.