TABLE 1.
Red cell binding and elution of hPIV1 and hPIV3
| Virus | Source of red cellsa | pH | HA titer (log2)b
|
||
|---|---|---|---|---|---|
| 4°C | After elution at 20°C | After rebinding at 4°C | |||
| hPIV1c | Chicken | 7 | 6 | 0 | 6 |
| 5 | 6 | 0d | 6 | ||
| Guinea pig | 7 | 2.5 | 2.5 | >8 | |
| 5 | 5.5 | 0 | >8 | ||
| hPIV3 | Human | 7 | ≤1 | 0 | 4 |
| 5 | 3 | 0 | 0 | ||
| Guinea pig | 7 | 3 | 0 | 4 | |
| 5 | 3 | 0 | 0 | ||
a
hPIV1 bound poorly to human red blood cells; hPIV3 did not bind chicken red cells.
b
Results are shown for one experiment, but the results with different HA amounts and different batches of red cells showed the same pattern.
c
The NA activity of hPIV1 was ∼1 nmol 3′-sialyllactose cleaved in 30 min per 50 μl virus. hPIV3 activity is too low to measure unless the virus is concentrated ∼100-fold.
d
In some experiments no elution was observed, but after mixing and resettling there was no rebinding at 22°C, indicating reduced avidity.