CD4 and infection: However, analysis of MusPV1 E1∧E4 spliced transcripts, as a measure of infection, at earlier time points (Figure 6E) revealed substantially higher numbers of MusPV1 E1∧E4 spliced transcripts relative to beta-actin in CD4 KO mice in the first three weeks post-infection, compared to wt C57BL/6 and CD8 KO mice.