Table 1.

Evaluation of the different titration methods

	RNA c/ml	TU/ml	pg p24/ml	TU/pg	TU/RNA
Cell factories
CH-eGFP-WS	2.68 ± 0.38 × 1010	2.23 ± 1.10 × 109	9.8 ± 5.3 × 106	228	0.0832
Culture dishes
H-eGFP	5.63 ± 0.50 × 1010	5.05 ± 4.9 × 107	4.67 ± 4.5 × 106	11	0.0009
H-eGFP-WS	3.83 ± 2.25 × 1010	2.92 ± 2.5 × 108	4.83 ± 4.70 × 106	60	0.0076
CH-eGFP-WS	2.73 ± 1.59 × 1010	1.68 ± 1.3 × 109	4.79 ± 3.45 × 106	351	0.0615

The lentiviral vector CH-eGFP-WS was produced in cell factories and concentrated by centrifugation as described before [8]. Three independent RNA extractions were carried out on this vector and RNA equivalents were determined by RT-qPCR. Mean values ± standard deviation are shown. Next, three lentiviral vectors with different transfer plasmids, H-eGFP, H-eGFP-WS and CH-eGFP-WS, were produced in parallel in cell culture dishes. RNA equivalents (RNA/ml), transducing units (TU/ml) and p24 concentrations (pg p24/ml) were determined by RT-qPCR, titration and ELISA, respectively. The TU/pg and TU/RNA value indicate the specific activity of the vector constructs and correlate well with the vector backbones. The data represent the mean values ± standard deviation of three independent productions per lentiviral vector.