Quantification of Lentiviral Vectors with Nucleic Acid Dyes

Lentiviral vectors are widely used in both biological research and therapeutic applications. Accurate and reliable quantification is essential for their effective use, yet existing methods are often technically demanding and time-consuming. Here, we describe a simple and robust approach to measure lentiviral titers by quantifying viral genomic RNA with nucleic acid-binding dyes. We first evaluated several newly developed commercially available fluorescent dyes for their ability to detect RNA and DNA, identifying SYBR Green II and SYBR Gold as the most sensitive for RNA, with detection limits in the low-nanogram range. We further observed that SYBR Green II readily stained nucleic acids in live cells, whereas SYBR Gold was only partially membrane-permeable. Based on these findings, we developed a quantification method combining SYBR Green II with benzonase to selectively detect encapsidated lentiviral RNA. This assay yielded results consistent with those obtained by enzyme-linked immunosorbent assays. Importantly, this SYBR Green II-based method is rapid (<60 min), reliable, and cost-effective, making it a practical tool for titering lentiviral vectors.