Figure 1
Quantitation of viral titer. Murine fibroblast NIH 3T3 cells (2 × 105) were transduced with (a) 1000μl, (b) 100μl, or (c) 10 μl of unconcentrated pRET2.EGFP supernatant. The percentage of enhanced green fluorescent protein (EGFP)-positive cells was measured by flow cytometry (% EGFP+ cells indicated in each panel). Titer was calculated using the volume of supernatant yielding <10% EGFP+ cells. In this example: Titer = 0.043 × (2 × 105 target cells) / 0.01 ml = 0.86 × 106 cfu/ml. For concentrated supernatant, smaller volumes were required to achieve transduction efficiencies <10%.