TABLE 5.
Biological properties of the cDNA-derived recombinant mutants
| Virus | Phenotype of the recombinant viruses on indicated cells
|
Attenuation in miced | |||||
|---|---|---|---|---|---|---|---|
| Vero
|
Neuro-2A
|
SH-SY5Y
|
|||||
| spa | tsb | tsb | hrc | tsb | hrc | ||
| 651/E-Leu119 | − | + | + | − | + | − | − |
| 651/E-Asn147 | − | − | + | − | + | − | − |
| 651/E-Asn205 | − | − | + | − | − | − | − |
| 651/E-Glu315 | + | + | + | + | + | − | + |
| 651/Ebox | + | − | + | + | + | − | + |
| 651/NS3-Glu46 | + | + | + | − | − | − | + |
| E5-104 | + | + | + | + | + | + | + |
Virus with a mean plaque diameter that was ≤25% of the plaque size (1.42 mm, diameter) of parental E5-651 virus (Fig. 2A) on Vero cells was designated as having the sp phenotype.
Temperature sensitivity was defined as a reduction of >2.0 log10 PFU/ml in virus titer in the indicated cells at 37°C compared to that for the titer achieved at the permissive temperature of 32°C. Data are derived from results presented in Table 3.
hr phenotype was defined as a 100-fold-or-greater reduction in virus titer in neuroblastoma cells at 32°C on day 5 compared to that achieved in Vero cells (Fig. 2B).
The mutant virus that showed a >4-day delay in the onset of encephalitis or death and caused less mortality/morbidity in SCID mice compared to that for E5-651 (Table 4) was considered as having an att phenotype.