Optimized protocol for high-titer lentivirus production and transduction of primary fibroblasts

The lentivirus-short hairpin RNA (shRNA) system is a widely used tool for RNA interference. Multiple factors may affect the RNA interference efficiency during lentivirus production and transduction procedures. Thus, an optimized protocol is required to achieve high-titer lentivirus and efficient gene delivery. In the present study, lentivirus was produced by transfecting lentiviral transfer and packaging plasmids into HEK 293T cells. The factors affecting lentiviral titer were assessed, including lentiviral plasmid ratio, lentiviral transfer plasmid type, serum type for cell culture, transfection reagent-plasmid mixture incubation time, and the inoculation density of 293T cells for transfection. The high-titer lentivirus was achieved when plasmids were transfected at a molar ratio of 1:1:1:2, and the transfection reagent-plasmid mixture was replaced 6-8 h after transfection. The pLVX-shRNA2 lentiviral transfer plasmid was associated with the highest lentiviral titer, while both pLVX-shRNA2 and psi-LVRU6GP plasmids were associated with efficient RNA interference in target cells. The serum type for 293T cell culture affected the lentiviral titer significantly, while the inoculation density of 293T cells showed no influence on transfection efficiency or lentiviral titer. Moreover, the human primary fibroblasts infected with lentivirus, using the centrifugation method, achieved higher transduction efficiency than those infected with the non-centrifugation method. In conclusion, this study helped optimize lentiviral production and transduction procedures for more efficient gene delivery.