Serum Antibodies Protect against Intraperitoneal Challenge with Enterotoxigenic Escherichia coli
Figure 2
Evaluation of the protective immunity of the detoxed CFA/I fimbriae. (a)–(d) Endpoint Ab titers were induced to detoxed CFA/I fimbriae. BALB/c mice (7/group) were i.m. immunized with (a) 60, (b) 100, (c) 150, or (d) 0 μg CFA/I fimbriae on days 0 and 14. Serum IgG and mucosal IgA anti-CFA/I fimbriae endpoint Ab titers were measured at 0, 2, and 3-wk postprimary immunization. IgG subclass responses were determined at wk 3, and *, **, and *** versus IgG1 titers. (e) Assessment of the protective efficacy against i.p. ETEC challenge was determined. CFA/I fimbriae-immunized mice (a)–(c) and sPBS-dosed mice (d) were i.p. challenged with CFUs of wt ETEC H10407 at 4-wk postprimary immunization. Mouse survival rates were observed for 14 days. The survival rates of 60 μg, 100 μg, and 150 μg CFA/I fimbriae-immunized mice were 100% (7/7), 71.4% (5/7), and 42.9% (3/7), respectively, versus 14.3% (1/7) for sPBS-dosed mice. Survival fractions obtained from vaccinated mice were compared to sPBS-dosed mice, and significance was determined: *.
