CD4 and HIV-1 infection: Importantly, VLP-Vpx treatment neither induces CD4+ T-cell activation and proliferation nor affects HIV-1 infection of activated CD4+ T-cells[10], indicating that SAMHD1 specifically restricts HIV-1 infection in resting CD4+ T-cells, but not in activated CD4+ T-cells despite comparable expression levels of endogenous SAMHD1 in these cells.