TABLE 3.
Immunogenicity and protective efficiency of rHMPV, rHMPVΔSH/G-FWT, and FAMPV-A in AGMs
| Virusa | Mean serum-neutralizing antibody titerb (reciprocal log2 ± SE)
|
Challenge virus replication after challengec from:
|
||||
|---|---|---|---|---|---|---|
| 28 Days postimmunization | 28 Days after challenge | Nasopharyngeal swab
|
Tracheal lavage
|
|||
| Duration of shedding (days ± SE) | Mean peak titer (log10 PFU/ml ± SE) | Duration of shedding (days ± SE) | Mean peak titer (log10 PFU/ml ± SE) | |||
| Mock | ≤1.5 | 9.2 ± 0.5 | 8.0 ± 1.0 | 4.0 ± 0.1 | 7.0 ± 0.0 | 4.9 ± 0.6 |
| rHMPV | 8.1 ± 0.4d | 8.3 ± 0.3 | 1.9 ± 0.8 | 0.9 ± 0.1 | 0.1 ± 0.1 | 0.7 ± 0.0 |
| FWT | 7.3 ± 0.2d | 7.0 ± 0.7 | 0.0 ± 0.0 | ≤0.7 | 0.0 ± 0.0 | ≤0.7 |
| FAMPV-A | 6.7 ± 0.6d | 8.2 ± 0.5 | 0.0 ± 0.0 | ≤0.7 | 0.0 ± 0.0 | ≤0.7 |
AGMs in groups of four (Fwt and FAMPV-A) or two (mock) animals were immunized by intranasal and intratracheal infections using a 1-ml inoculum per site containing 6.0 log10 PFU of the indicated virus or L15 medium (mock). Two animals were inoculated with rHMPV in parallel; results from 10 animals which were inoculated with rHMPV under identical conditions in previous experiments were included.
Sera were collected on days 0 and 28 following the first infection, and the neutralizing antibody titer against HMPV was determined. The preinfection anti-HMPV serum titers were ≤1.5 (reciprocal log2) for each animal in the study.
On day 28, AGMs from each group were challenged intranasally and intratracheally with 6.0 log10 PFU of rHMPV. The level of virus replication is expressed as the geometric mean of the peak virus titers (log10 PFU/illiliter ± standard errors) for the animals in each group irrespective of sampling day. The lower limit of detection is 0.7 log10 PFU/ml. A value of 0.7 log10 PFU/ml is assigned to samples with no detectable virus.
Not statistically different (P < 0.05) by the analysis of variance/Tukey-Kramer post-hoc test.