SAMHD1 and infection: Statistical comparison of Gag and SAMHD1 levels in SIV- and HIV-1-infected cells (Figure 1C, D) confirmed that not only do both HIV-1 and SIV infect macrophages at comparable levels (30% +/− 4.4% for HIV-1 and 48% +/− 6.1% for SIV), but only SIV infection of macrophages led to elimination of SAMHD1.