For example, although both Tem and Tcm have been implicated in HIV persistence,42–45 Tem are more susceptible to in vitro HIV infection than their Tcm counterparts.41,46 Unsupervised hierarchical clustering of manually gated CD4+ Tcm and Tem across tissue sites revealed that, overall, Tem expressed lower levels of VISORs than did Tcm (Figure 2C), in line with Tem’s increased susceptibility to HIV infection. This evidence concerns the gene CD4 and HIV infectious disease.