TABLE 2.

Temperature sensitivity and attenuation phenotype of rHPIV1 L protein codon 942 substitution mutants

VirusNo. of nucleotide changes needed to restore wild-type amino acidVirus titer at 32°C (log10 TCID50/ml)Mean log10 reduction in virus titer at indicated temp (°C)aReplication of virus in hamsters
No. of animalsMean titer of virus (log10 TCID50/g ± SE)
3536373839Nasal turbinatesLungs
rHPIV1 wild type07.80.10.40.81.51.8304.2 ± 0.23.9 ± 0.4
rHPIV1-Y942Hcp4518.01.43.15.15.818<1.5 ± 0.0b<1.5 ± 0.0
rHPIV1-Y942C18.01.82.12.34.86.564.4 ± 0.23.4 ± 0.4
rHPIV1-Y942F18.10.31.31.93.45.463.8 ± 0.13.9 ± 0.2
rHPIV1-Y942N19.01.02.13.74.37.062.0 ± 0.21.6 ± 0.1
rHPIV1-Y942D17.93.35.3>6.6>6.7>6.961.6 ± 0.11.8 ± 0.3
rHPIV1-Y942S28.30.61.23.65.2>6.463.2 ± 0.11.8 ± 0.2
rHPIV1-Y942W28.40.81.53.04.2>6.4121.8 ± 0.21.6 ± 0.1
rHPIV1-Y942Q27.01.43.6>4.7>5.8>5.9121.5 ± 0.11.7 ± 0.2
rHPIV1-Y942M37.33.05.3>6.0>5.8>6.26<1.5 ± 0.0<1.5 ± 0.0
rHPIV1-Y942A38.13.53.5>5.1>6.4>6.86<1.5 ± 0.0<1.5 ± 0.0
rHPIV1-Y942T38.01.83.0>5.0>6.8>6.96<1.5 ± 0.0<1.5 ± 0.0
rHPIV1-Y942G38.11.03.1>4.1>5.8>7.36<1.5 ± 0.0<1.5 ± 0.0
rHPIV1-Y942V37.02.65.0>5.7>5.8>6.112<1.5 ± 0.01.6 ± 0.1
rHPIV1-Y942L37.02.85.05.55.5>5.86<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.