TABLE 1.
Efficiency of PR8 generation in MDCK cells
| Expt | Infectivity titer (PFU/ml)a
|
|||
|---|---|---|---|---|
| pPolIC250 (PR8)b
|
pPolIC457 (PR8)c
|
|||
| Trypsin−d | Trypsin+e | Trypsin− | Trypsin+ | |
| 1 | 2.5 × 102 | 1.9 × 104 | 1.3 × 102 | 3.0 × 104 |
| 2 | 2.5 × 103 | 7.8 × 104 | 1.4 × 102 | 5.0 × 103 |
| 3 | 4.6 × 102 | 1.3 × 104 | 1.5 × 103 | 1.4 × 104 |
a
At 48 h after transfection, virus titers in the supernatant were determined by plaque assays of MDCK cells. The results are from three independent experiments (experiments 1 to 3).
b
pPolIC250 (PR8) indicates transfection of cells with pPolIC250-PB2, -PB1, -PA, -HA, -NP, -NA, -M, and -NS and pCAGGS-PB2, -PB1, -PA, and -NP.
c
pPolIC457 (PR8) indicates transfection of cells with pPolIC457-PB2, -PB1, -PA, -HA, -NP, -NA, -M, and -NS and pCAGGS-PB2, -PB1, -PA, and -NP.
d
Trypsin−, cells were cultured with trypsin-free Opti-Mem.
e
Trypsin+, cells were cultured with Opti-Mem containing trypsin.