Table 2.
Properties of 1:7 recombinant and parental influenza viruses used in this study
| Virus stock* | Stock titer, pfu/ml | Weight loss, %† | LD50‡ |
|---|---|---|---|
| 1918 PA:Tx | 5.8 × 108 | 4.7 | >6 |
| 1918 PB1:Tx | 3.4 × 108 | 9.2 | >6 |
| 1918 PB2:Tx | 1.1 × 108 | 11.8 | >6 |
| 1918 HA/NA:Tx | 2.1 × 107 | 24.6 | 4.25 |
| 1918 HA:Tx | 2.1 × 107 | 23.7 | 4.25 |
| 1918 NP:Tx | 1.1 × 108 | 5.7 | >6 |
| 1918 NA:Tx | 9.2 × 107 | 13.1 | >6 |
| 1918 M:Tx | 1.1 × 108 | 3.3 | >6 |
| 1918 NS:Tx | 3.2 × 107 | 5.3 | >6 |
| Tx/91 | 2.1 × 108 | 6.1 | >6 |
*Prepared on MDCK cells with trypsin and incubated for 48–72 h.
†Maximum percent weight loss (mean of six mice per group) after infection with 106 pfu of virus.
‡Expressed as the log10 pfu required to give 1 LD50.