SAMHD1 and infection: SAMHD1, a pyrophosphatase that limits availability of dNTPs for reverse transcription in resting cells and terminally differentiated cells such as MDMs [92,93], is degraded by Vpx/Vpr alleles derived from several primate lentiviral lineages, including SIVsm/SIVmac/HIV-2 in a CUL4A dependent manner [94,95], thus facilitating robust reverse transcription and infection of non-dividing cells including dendritic cells and macrophages [92,93,96].