S100B and HIV-1 infection: To examine the effects of SAMHD1 on HIV-1 infection in the monocytic THP-1 cell line, THP-1 control (Ctrl) and SAMHD1 knock-out (KO) cell lines were infected with a single-cycle luciferase reporter HIV-1 (HIV-1-Luc/VSV-G), which lacks viral envelope protein and Nef (24).