TABLE 1.
Protection induced by the attenuated rHRSV vaccine candidate against challenge with human wtHRSV (3 × 105 TCID50) in old cotton ratsa
| No. of animals | Age (mo) | Vaccine | Dose (TCID50) | Lung virus titer |
Nose virus titer |
||
|---|---|---|---|---|---|---|---|
| % positive | Titer (SD) | % positive | Titer (SD) | ||||
| 3 | 8 | Mock | 100 | 4.9 (0.4) | 100 | 4.2 (0.6) | |
| 6 | 8 | rHRSV | 103 | 100 | 3.8 (0.7) | 100 | 3.7 (1.5) |
| 6 | 8 | rHRSV | 104 | 100 | 2.9 (0.3) | 100 | 1.2 (1.5) |
| 5 | 8 | rHRSV | 105 | 20 | 3.6 | 40 | 2.8 (0) |
| 6 | 8 | wtHRSV | 104 | 0 | 16 | 2.1 | |
a
As a positive control, one group was immunized with 104 TCID50 of wtHRSV. Shown are the percentage of animals that showed HRSV 5 days after challenge and the mean titer detected in infected animals per group for lungs and nose. As a control for age effects in old cotton rats shown in this table, young animals were vaccinated at 2 months of age with mock vaccine or with rHRSV at 103 TCID50 and challenged. Of these young mock-immunized animals, 100% of animals had HRSV titers in lungs upon challenge. Of the young animals immunized with rHRSV at 103 TCID50, 0% of animals had HRSV titers in lungs upon challenge.