TCF7 and infection: Mice were intraperitoneally injected with tamoxifen at 10 days after Cl13 infection (Strategy I) or 4 days before Cl13 infection (Strategy II) to knock out TCF1 expression in T cells of Tcf7fl/flERT2-Cre mice at either the advanced or early stage of Cl13 chronic infection (Figures 4A,E).