Figure 6. MA-ExoN vaccination protects from lethal challenge.

(a,b) Low-passage MA-ExoN and mock (PBS) vaccinations of 12-month-old female BALB/c mice followed by lethal challenge with MAwt. (a) Weight loss in challenged mice. Dark circles, 10⁴ PFU MA-ExoN vaccination; white circles, 10^2.5 PFU MA-ExoN vaccination; dark triangles, PBS vaccination. Error bars indicate s.d. (b) Lung titers at day 2 after challenge. ExoN was given at a 2.5log (10^2.5 PFU) vaccination. The mean titer is indicated by a bar in each group. (c) Fifty-percent plaque reduction neutralization titer (PRNT₅₀) assay using sera from PBS-vaccinated and MA-ExoN–vaccinated mice to neutralize MAwt. Reciprocal dilutions capable of effecting 50% plaque reduction are shown by circles; mean reciprocal dilutions are indicated by a bar for each group. The limit of detection for each assay, if given, is indicated by a dashed line.