CD4 and infection: Analysis of CD4+ T cell subsets revealed an increase in TFH cells and IFNγ-, IFNγ+ TNF+-, and IL-2-producing CD4+ T cells and a decrease in Treg cells in Mock-immune compared with ZIKV-immune mice (S5E–S5G Fig), which is consistent with the observation that Treg cell number peaks at day 3 after primary infection (Fig 2D).