Figure 8. Protection of ffLAC-4 vaccination against respiratory A. baumannii infection. Groups of five young and aged mice were immunized intramuscularly with 1×107 CFU of ffLAC-4 or PBS on day 0. On day 7, mice were challenged intratracheally with 1.5×107 CFU of LAC-4. (A) Clinical score and (B) survival rate of mice were monitored for 7 days after infection. Clinical score is expressed as means ± SEM. The data represent one of 2 independent experiments. Survival curves were compared using log-rank test. Statistical significance of clinical score was determined by Student’s t test. **, P < 0.01 immunized aged mice versus immunized young mice.