While mutation of the NF-κB–binding motifs moderately impairs proviral expression in immortalized T cells (measured after single round infection of SupT1, Jurkat, and PM1) [109], binding of NF-κB or NFAT to these cis-acting elements are critical for provirus activation in primary systems (CD4+ T cells) [106,110,111]. Here, CD4 is linked to infection.