Mice (N = 15) were immunized at days 0, 21 and 42 by the indicated antigens (or by adjuvant + PBS for controls) and routes. Six weeks after the last immunization, at day 84, 100 LD 50 of S. Typhimurium (A, B) or S. flexneri 2a (C, D) was administered (intragastrically and intranasally, respectively) to SipD (A, D) or IpaD (B, C) immunized mice. Survival was monitored for 21 days. Statistical significance was determined using a log-rank (Mantel-Cox) test. Statistically significant differences are indicated by **** p < 0.0001, *** 0.0001 < p < 0.001, and ** 0.001 < p < 0.01. Exact p value indicated in the figure. ns: non-significant) compared to PBS groups.