Fig 3. Multistep growth curve of rHPIV3 vectors expressing RSV F.

Vero cells were infected in triplicate with an MOI of 0.01 TCID₅₀/cell of the indicated viruses. Cells were incubated at 32°C and aliquots of culture medium were collected at 24 h intervals over 7 days and replaced by equal volumes of fresh medium. Samples were flash frozen and at a later time virus titers were determined in parallel by limiting dilution on LLC-MK2 cells using an hemadsorption assay, and are reported as log₁₀TCID₅₀ per mL. Mean titers are shown with the standard deviations indicated as vertical error bars. The statistical significance of the differences between the vectors expressing RSV F versus wt rHPIV3 empty backbone on day 3 and 7 post-infection was determined by one-way analysis of variance with Tukey’s multiple-comparisons post-test and are indicated by ** (P<0.01) and **** (P<0.0001).