This system has been used to perform in vivo studies of autologous CD34+ HSPCs transduced with the H1-CCR5 shRNA 1005 vector and showed effective down-regulation of the HIV-1 co-receptor, CCR5, which protected mouse-derived human splenocytes ex vivo (80) and CD4+ T cells in vivo (81) from CCR5-tropic HIV-1 infection. This evidence concerns the gene CD4 and HIV-1 infection.