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 |
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.
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.
Virus stock was prepared with MDCK cells. Viruses were harvested when cytopathic effects became advanced.
NA, not applicable.
Descriptions of the A/B constructs are given in the first paragraph of Results.