Fig. 2

Real-time PCR quantitation of JCV DNA in virus suspensions following ultrafiltration. The standard virus suspensions, which contain the indicated amounts of JCV were left untreated (standard procedure) or concentrated from 4 mL to 500 μL in volume by using the ultrafiltration device (ultrafiltration procedure) as described in the legend of Fig. 1. Total 25-μL DNAs were extracted from a 500-μL sample, and the copy numbers of the JCV DNA per PCR reaction (5 μL template) were determined (a). The copy numbers of JCV DNA per mL were calculated with respect to total volume of DNA extracts (5-fold) and the amounts of test samples (either 2-fold for standard procedure or 0.25-fold for ultrafiltration procedure) (b). Data are shown as means ± standard errors of the means from four separate experiments. Sharp symbols indicate that JCV DNA was under the detection level. Statistically significant differences in the copy numbers of JCV DNA following the standard and ultrafiltration procedures are indicated by asterisks (p < 0.05). Statistical analyses were performed only on the data shown in panel B because the initial volume and concentration ratio for the data of panel A are not equal between each procedure