CCR5 and infection: Consistent with Vpr’s well-known ability to transactivate LTR-driven viral gene expression [9], [10], [25], we observed that gag mRNA levels was significantly increased in HIV-1 Vpr+ infected HuT/CCR5 cells compared to the HIV-1 Vpr− infected cells, which appears to be the main contributing factor for the enhanced infection of single cycle HIV-1 expressing Vpr.