TABLE 1.
Comparison between PEG-induced infectivity and infectious centersa
| Virus | MDBK
|
NB
|
||
|---|---|---|---|---|
| Infectivity | Infect. centers | Infectivity | Infect. centers | |
| PrV-1112 | 1.0 × 108 | 1.0 × 108 | 8.9 × 107 | 4.0 × 107 |
| 9.3 × 107 | 9.9 × 107 | 8.4 × 107 | 3.7 × 107 | |
| PrV gD− Pass | 4.0 × 106 | 2.1 × 106 | 9.2 × 105 | 2.9 × 105 |
| 5.6 × 104 | 9.0 × 104 | 9.3 × 104 | 4.6 × 104 | |
| PrV gCD− Pass | 1.2 × 103 | 1.3 × 103 | 3.9 × 102 | 2.9 × 102 |
| 7.8 × 103 | 3.7 × 103 | 9.8 × 102 | 8.3 × 102 | |
a
MDBK and NB cells were inoculated with serial dilutions of the indicated virus stock and treated with PEG. Thereafter, one well was stained after 48 h with X-Gal and plaques or infected single cells (for PrV gD− Pass and PrV gCD− Pass on NB cells) were counted. A parallel well was trypsinized and reseeded together with excess MDBK cells. At 48 h after infection, plaques were stained with X-Gal and counted. Indicated are titers determined directly (Infectivity) compared to titers determined in infectious-center assays (Infect. centers). Representative data (in infectious units per milliliter of virus suspension) from two independent experiments each are shown.