Figure 4.

Protective efficacy of rIpaB and rIpaB+rGroEL immunization on survival. Groups of female BALB/c mice (n=10) were immunized i.n. with 40 µg/mouse of rGroEL/rIpaB/rIpaB+rGroEL. Subsequent booster doses were given on the seventh and twenty-eighth days. The control group of mice (n=10) was immunized with sterile PBS. Fifteen days after the last booster dose, mice were challenged with a lethal dose of 1×10⁷ CFU/mouse i.n. of (a) S. flexneri, (b) S. boydii or (c) S. sonnei. Another group of 10 mice was passively immunized i.n. with 30 µl of heat inactivated immune sera raised from the mice immunized with rGroEL/rIpaB/rIpaB+rGroEL and these mice were challenged with a lethal dose of 1×10⁷ CFU/mouse i.n. of (d) S. flexneri, (e) S. boydii or (f) S. sonnei. All groups of mice were observed for mortality for 30 days. CFU, colony forming units; i.n., intranasally.