Plasmids pcDNA5-Dual-HIV(-1) and (0) were made by inserting the HindIII-ApaI fragment from pDual-HIV(-1) or (0), respectively, into pcDNA5-FRT (Invitrogen), which contains a resistance gene to hygromycin B. An in-frame construct without the HIV-1 frameshift region was generated by cloning an oligonucleotide cassette (inframe-fwd and inframe-rev) into the KpnI and BamHI restriction sites of linearized pDual-HIV. In pDual-in-frame, the luciferase coding sequences are in the same reading frame and separated by a short linker. The HindIII-ApaI fragment from pDual-in-frame was cloned into pcDNA5-FRT.