TABLE 2.
Temperature sensitivity and attenuation phenotype of rHPIV1 L protein codon 942 substitution mutants
| Virus | No. of nucleotide changes needed to restore wild-type amino acid | Virus titer at 32°C (log10 TCID50/ml) | Mean log10 reduction in virus titer at indicated temp (°C)a
|
Replication of virus in hamsters
|
||||||
|---|---|---|---|---|---|---|---|---|---|---|
| No. of animals | Mean titer of virus (log10 TCID50/g ± SE)
|
|||||||||
| 35 | 36 | 37 | 38 | 39 | Nasal turbinates | Lungs | ||||
| rHPIV1 wild type | 0 | 7.8 | 0.1 | 0.4 | 0.8 | 1.5 | 1.8 | 30 | 4.2 ± 0.2 | 3.9 ± 0.4 |
| rHPIV1-Y942Hcp45 | 1 | 8.0 | 1.4 | 3.1 | 5.1 | 5.8 | 18 | <1.5 ± 0.0b | <1.5 ± 0.0 | |
| rHPIV1-Y942C | 1 | 8.0 | 1.8 | 2.1 | 2.3 | 4.8 | 6.5 | 6 | 4.4 ± 0.2 | 3.4 ± 0.4 |
| rHPIV1-Y942F | 1 | 8.1 | 0.3 | 1.3 | 1.9 | 3.4 | 5.4 | 6 | 3.8 ± 0.1 | 3.9 ± 0.2 |
| rHPIV1-Y942N | 1 | 9.0 | 1.0 | 2.1 | 3.7 | 4.3 | 7.0 | 6 | 2.0 ± 0.2 | 1.6 ± 0.1 |
| rHPIV1-Y942D | 1 | 7.9 | 3.3 | 5.3 | >6.6 | >6.7 | >6.9 | 6 | 1.6 ± 0.1 | 1.8 ± 0.3 |
| rHPIV1-Y942S | 2 | 8.3 | 0.6 | 1.2 | 3.6 | 5.2 | >6.4 | 6 | 3.2 ± 0.1 | 1.8 ± 0.2 |
| rHPIV1-Y942W | 2 | 8.4 | 0.8 | 1.5 | 3.0 | 4.2 | >6.4 | 12 | 1.8 ± 0.2 | 1.6 ± 0.1 |
| rHPIV1-Y942Q | 2 | 7.0 | 1.4 | 3.6 | >4.7 | >5.8 | >5.9 | 12 | 1.5 ± 0.1 | 1.7 ± 0.2 |
| rHPIV1-Y942M | 3 | 7.3 | 3.0 | 5.3 | >6.0 | >5.8 | >6.2 | 6 | <1.5 ± 0.0 | <1.5 ± 0.0 |
| rHPIV1-Y942A | 3 | 8.1 | 3.5 | 3.5 | >5.1 | >6.4 | >6.8 | 6 | <1.5 ± 0.0 | <1.5 ± 0.0 |
| rHPIV1-Y942T | 3 | 8.0 | 1.8 | 3.0 | >5.0 | >6.8 | >6.9 | 6 | <1.5 ± 0.0 | <1.5 ± 0.0 |
| rHPIV1-Y942G | 3 | 8.1 | 1.0 | 3.1 | >4.1 | >5.8 | >7.3 | 6 | <1.5 ± 0.0 | <1.5 ± 0.0 |
| rHPIV1-Y942V | 3 | 7.0 | 2.6 | 5.0 | >5.7 | >5.8 | >6.1 | 12 | <1.5 ± 0.0 | 1.6 ± 0.1 |
| rHPIV1-Y942L | 3 | 7.0 | 2.8 | 5.0 | 5.5 | 5.5 | >5.8 | 6 | <1.5 ± 0.0 | <1.5 ± 0.0 |
a
Mean titer reduction compared to titer at 32°C. Each values represents the average of at least three experiments. A mutant is considered to be temperature sensitive if its reduction in titer at a nonpermissive temperature is 100-fold greater than the reduction in titer of the wild type HPIV1 tested at that temperature (indicated by values in bold).
b
Each underlined value represents a greater-than-100-fold reduction compared to that for rHPIV1.