TABLE 1.
Properties of chimeric HAs expressed in cells and viruses
| HA construct | Property in cell culturea
|
Generation of virus possessing this geneb | Virus titer in supernatant of transfected cellb (TCID50/ml) | Virus titer of stockc (TCID50/ml) | ||
|---|---|---|---|---|---|---|
| Cell surface expression | Hemadsorption | Fusion | ||||
| Wild type | ||||||
| WSN-HA | + | + | + | + | 3.2 × 107 | 6.3 × 107 |
| B-HA | + | + | + | − | NAd | NA |
| Chimerice | ||||||
| ANBH | + | + | + | + | 2.0 × 10 | 6.3 × 102 |
| ANSBH | + | + | + | + | 1.1 × 102 | 2.0 × 106 |
| ANTBH | + | + | + | + | 2.0 × 104 | 6.3 × 106 |
| ANSTBH | + | + | + | + | 1.1 × 106 | 3.6 × 106 |
| ANBW | + | − | − | − | NA | NA |
| ANSBW | + | − | − | − | NA | NA |
a
Each HA construct was transfected into COS-7 cells together with type A polymerase- and NP-expressing plasmids. Biological assays were conducted at 48 h posttransfection.
b
Virus possessing the wild-type or a chimeric HA gene together with other influenza A virus genes was generated by plasmid-based reverse genetics. At 48 h posttransfection, the supernatant of transfected 293T cells was harvested and titrated for infectivity.
c
Virus stock was prepared with MDCK cells. Viruses were harvested when cytopathic effects became advanced.
d
NA, not applicable.
e
Descriptions of the A/B constructs are given in the first paragraph of Results.