TABLE 2.
Immunogenicity and protective efficiency of gene deletion rHMPVs in hamsters
| Immunizing virusa | Inoculum (log10 TCID50/animal) | Mean serum neutralizing antibody titer (log2 ± SE)b
|
Challenge virus replication on day 3 postchallenge
|
||||
|---|---|---|---|---|---|---|---|
| Preimmunization | 27 days postimmunization | Nasal turbinates
|
Lungs
|
||||
| % with detectable challenge virus | Mean titer (log10 TCID50/g of tissue ± SE)c | % with detectable challenge virus | Mean titer (log10 TCID50/g of tissue ± SE)c | ||||
| Mock | <3.3 ± 0.0 | <3.3 ± 0.0 | 100 | 6.5 ± 0.1 | 100 | 4.8 ± 0.3 | |
| rHMPV | 5.7 | <3.3 ± 0.0 | 10.0 ± 0.2 | 0 | ≤1.5 ± 0.0 | 0 | ≤1.5 ± 0.0 |
| ΔSH | 5.7 | <3.3 ± 0.0 | 10.4 ± 0.2 | 0 | ≤1.5 ± 0.0 | 0 | ≤1.5 ± 0.0 |
| ΔSH/G | 5.7 | <3.3 ± 0.0 | 7.6 ± 0.3 | 40 | 3.0 ± 0.8d | 0 | ≤1.5 ± 0.0 |
| ΔG | 5.2 | <3.3 ± 0.0 | 7.5 ± 0.5 | 100 | 4.0 ± 0.5 | 0 | ≤1.5 ± 0.0 |
Hamsters in groups of six (or five for ΔSH/G) were immunized by intranasal infection with 5.2 or 5.7 log10 TCID50 as indicated of the indicated virus or mock infected with L15 medium (mock).
Sera were collected 2 days before and 27 days following the first infection, and the neutralizing antibody titer against HMPV83 was determined. The preinfection anti-HMPV serum titers were <3.3 (reciprocal log2) for all animals in the study.
On day 28, hamsters from each group were challenged intranasally with 5.7 log10 TCID50 of HMPV83. Nasal turbinates and lungs were harvested 3 days later, and the virus titers were determined on LLC-MK2 cells.
The value of 1.5 log10 TCID50/g of tissue (the lower limit of detection for virus) was assigned to nonshedding animals to calculate the mean titer.