TABLE 5.
Temperature sensitivity and attenuation phenotype of rHPIV1 L protein codon-992 substitution mutants
| Virus | No. of nucleotide changes needed to restore wild-type amino acid | Virus titer at 32°C (log10 TCID50/ml)b | Mean log10 reductiona in virus titer at indicated temp (°C)
|
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 | 7.5 | 0.1 | 0.1 | 0.5 | 0.6 | 1.2 | 30 | 4.2 ± 0.2 | 3.9 ± 0.4 |
| rHPIV1 L992Fcp45 | 1 | 8.1 | 0.2 | 0.3 | 1.3 | 0.9 | 2.4 | 12 | 4.4 ± 0.3 | 3.0 ± 0.2 |
| rHPIV1 L992M | 1 | 8.4 | 0.2 | 0.2 | 0.4 | 0.7 | 2.7 | 6 | 4.7 ± 0.3 | 3.2 ± 0.4 |
| rHPIV1 L992I | 1 | 8.2 | 0.3 | 0.5 | 0.5 | 2.7 | 4.3b | 6 | 4.1 ± 0.2 | 2.6 ± 0.3 |
| rHPIV1 L992W | 1 | 8.5 | 0.0 | 0.5 | 0.8 | 3.7 | 3.8 | 6 | 4.0 ± 0.2 | 3.3 ± 0.1 |
| rHPIV1 L992H | 1 | 8.1 | 0.3 | 1.3 | 1.3 | 1.8 | 4.9 | 6 | 3.3 ± 0.2 | 3.4 ± 0.1 |
| rHPIV1 L992V | 1 | 6.2 | 0.7 | 0.5 | 1.5 | 2.5 | 4.0 | 6 | <1.5 ± 0.0c | 1.7 ± 0.2 |
| rHPIV1 L992N | 2 | 7.8 | 0.6 | 0.3 | 0.6 | 2.0 | 3.3 | 6 | 2.7 ± 0.2 | <1.5 ± 0.0 |
| rHPIV1 L992Y | 2 | 8.5 | 0.0 | 0.2 | 0.5 | 1.4 | 2.9 | 6 | 4.5 ± 0.2 | 3.3 ± 0.4 |
| rHPIV1 L992K | 2 | 8.6 | 0.0 | 1.2 | 0.2 | 1.8 | 3.0 | 6 | 4.1 ± 0.3 | 3.1 ± 0.4 |
| rHPIV1 L992A | 2 | 7.9 | 0.5 | 0.3 | 1.2 | 3.0 | 4.5 | 6 | 3.6 ± 0.2 | 3.2 ± 0.3 |
| rHPIV1 L992C | 2 | 7.3 | 0.7 | 2.2 | 2.9 | 4.0 | >4.9 | 6 | 3.2 ± 0.2 | 1.7 ± 0.1 |
a
Mean reduction in titer compared to titer at 32°C. Each value represents the average of two or three experiments.
b
A mutant is considered to be temperature sensitive if its reduction in titer at a nonpermissive temperature is 100-fold greater than the reduction of titer of the wild-type HPIV1 tested at that temperature (indicated by values in bold).
c
Underlined values represent greater-than-100-fold reduction compared to that for rHPIV1 in the same pulmonary compartment.