Vpr is required for HIV-1 replication in the permissive and semi-permissive NKR clones. Wild-type (WT) HIV-1 (NL4-3) replication was measured in NKR and its subclones by p24Gag ELISA (A). In addition, WT, ΔVif, ΔVpr, and ΔVpu HIV-1 replication was compared in SS (B), H9 (C), N5-P (D), and N8-SP (E) cells. Data represent one of at least three independent experiments. (F) Endogenous SAMHD1 expression in the indicated cell lines was determined by Western blotting, and the amounts of actin were used as loading control.