Fig. 2: Protective efficacy of the recombinant antigens after intranasal immunization of mouse.

a Immunization schedule, sample collection, and bacterial challenge of BALB/c mice. Blood and stool samples were collected before each immunization dose and 12 days after the last immunization. b Mouse survival assay. Kaplan-Meyer plot of cumulative mortality of mice immunized intranasally with the vehicle or the recombinant protein antigens. Mice (n = 10/group) were challenged with S. Typhi 12 days after the last immunization dose and were monitored for 10 days. Significance was calculated by comparing the survival of the mice immunized by rCTB-T2544 with T2544 by Log-Rank Mantel Cox test. ***p = 0.0001 c In parallel experiments, mice immunized as above were subjected to ileal loop assay by injecting 100 ng of cholera toxin into each loop. The animals (n = 8/group) were checked for fluid accumulation in the ileal loops after 8 hours. d Fluid accumulation was measured by calculating the weight divided by the length of individual loops. Significance was calculated by comparing the loop weight/ length ratio of CTB-T2544 group with the T2544 and PBS immunized group, using one-way ANOVA with post hoc analysis using Tukey’s multiple comparison test. Data represented as mean with SD; ****p value < 0.0001 vs. T2544 and PBS. Error bars represent SD.