Table 1. Viruses generated in this study.
na, Not applicable.
| Virus | Origin of:* | |||
| HA gene | NA gene | PB2 gene | Remaining genes | |
| Wild-type PR8 | PR8 | PR8 | PR8 | PR8 |
| PR8/PB2–GFP | PR8 | PR8 | PB2(120)GFP(120) | |
| PR8ΔPB2 | PR8 | PR8 | na | |
| WSN/PB2–GFP | WSN | WSN | PB2(120)GFP(120) | |
| CA04/PB2–GFP | CA04 | CA04 | PB2(120)GFP(120) | |
| VN1203/PB2–GFP | VN1203 | VN1203 | PB2(120)GFP(120) | |
| PR8/PB2–Rluc | PR8 | PR8 | PB2(120)Rluc(120) | |
| PR8/PB2–Fluc | PR8 | PR8 | PB2(120)Fluc(120) | |
| CA04/PB2–Rluc | CA04 | CA04 | PB2(120)Rluc(120) | |
*
PR8, A/Puerto Rico/8/34 (H1N1); WSN, A/WSN/33 (H1N1); CA04, A/California/04/09 (H1N1); VN1203, A/Vietnam/1203/04 [H5N1; the various basic amino acid residues in the HA cleavage site (RERRRKKR↓G) were replaced with a non-virulent-type cleavage sequence (RETR↓G)]. PB2(120)GFP(120), PB2(120)Rluc(120) and PB2(120)Fluc(120) are the GFP, firefly luciferase and Renilla luciferase genes, respectively, flanked by the 3′ and 5′ non-coding sequences and 120 nt of the 3′ and 5′ coding sequences of the PB2 gene.