Table 2.
Level of temperature sensitivity of replication of rHPIV1 mutants in vitro.
| Mean reduction (log10) in virus titer ± S.E. at the indicated temperature compared to 32°C c | |||||||||
| Virus a | Virus titer ± S.E. at 32°C b | 35°C | 36°C | 37°C | 38°C | 39°C | 40°C | Shut-off (°C) d | |
| 1 | HPIV1 wt | 7.7 ± 0.1 | 0.1 ± 0.1 | 0.1 ± 0.1 | 0.2 ± 0.1 | 0.7 ± 0.1 | 1.3 ± 0.1 | 3.0 ± 0.3 | - |
| 2e | rHPIV1-CR84G | 9.2 ± 0.4 | 0.4 ± 0.2 | 0.4 ± 0.6 | 0.8 ± 0.5 | 0.3 ± 0.4 | 1.8 ± 0.6 | 4.5 ± 0.9 | - |
| 3e | rHPIV1-CR84GHNT553A | 7.8 ± 0.1 | -0.3 ± 0.2 | -0.3 ± 0.2 | -0.2 ± 0.2 | 0.1 ± 0.2 | 0.7 ± 0.2 | 2.5 ± 0.6 | - |
| 4e | rHPIV1-CΔ170 | 7.9 ± 0.3 | 0.2 ± 0.2 | 0.7 ± 0.8 | 0.5 ± 0.2 | 1.0 ± 0.3 | 2.6 ± 0.7 | 4.5 ± 1.0 | - |
| 5 | rHPIV1-LY942A | 8.0 ± 0.1 | 0.2 ± 0.3 | 1.2 ± 0.3 | 2.6 ± 1.1c,d | 6.4 ± 0.4 | ≥6.8 f | ≥6.8 | 37°C |
| 6e | rHPIV1-CR84GHNT553ALY942A | 7.4 ± 0.2 | 0.4 ± 0.4 | 0.5 ± 0.4 | 2.3 ± 0.4 | 4.0 ± 0.6 | 6.0 ± 0.4 | ≥6.4 | 37°C |
| 7 | rHPIV1-CR84GLΔ1710–11 | 7.5 ± 0.7 | 0.8 ± 0.7 | 3.0 ± 0.6 | 4.8 ± 0.2 | ≥6.3 | ≥6.3 | ≥6.3 | 36°C |
| 8 | rHPIV1-CR84G/Δ170HNT553ALY942A | 6.3 ± 0.1 | 0.3 ± 0.2 | 0.9 ± 0.6 | 2.0 ± 0.3 | 4.9 ± 0.2 | ≥5.1 | ≥5.1 | 38°C |
| 9 | rHPIV1-CR84G/Δ170HNT553ALΔ1710–11 | 6.4 ± 0.3 | 2.6 ± 0.6 | 4.0 ± 0.4 | ≥5.2 | ≥5.2 | ≥5.2 | ≥5.2 | 35°C |
a Data are the mean of three to sixteen experiments.
b Viruses were titrated on LLC-MK2 cells at either permissive (32°C) or potentially restrictive (35°C – 40°C) temperatures for 7 days and virus titers are expressed as the mean ± standard error (S.E.). The limit of detection was 1.2 log10 TCID50/ml.
c Values in bold indicate restricted replication, where the mean log10 reduction in virus titer at the indicated temperature vs 32°C was 2.0 log10 or greater than the difference in titer of HPIV1 wt at the same temperature vs 32°C. A virus is designated ts if restricted replication at 35°C–40°C is observed.
d Underlined values indicate viral shut-off temperature, the lowest temperature at which restricted replication is observed.
e These data have been previously published [13] [15] [16] and are included here for the purposes of comparison.
f The symbol "≥" indicates that virus titers were at the limit of detection and therefore the reduction in virus titer versus 32°C is greater than or equal to the indicated value. There is no S.E. value for viruses at the limit of detection.