Lentiviral Vector Encoding HPV-18 E2 Protein

HPV-18 E2 ORF was synthetized and cloned by Genscript into the bicistronic lentiviral vector pLVX-IRES-ZsGreen (Clontech, Mountain View, CA, USA). The sequence was partially modified to optimize translation of E2 (Supplementary Fig. 1). Lentiviral particles were produced by co-transfection of lentiviral vector encoding HPV-18 E2, or the empty vector as control (ZsGreen), with the ViraPower packaging system (Invitrogen, MA, USA) into HEK293T cells, using Lipofectamine2000 (Invitrogen, MA, USA) according to manufacturer’s directions [14 (link)]. After 48 h, viral particles were harvested and concentrated by ultracentrifugation, and the viral titer was determined by serial dilutions using HEK293FT cells, followed by flow cytometry analysis of ZsGreen expression 72 h post-transduction (BD FacsCanto II).