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. 2004 Nov;72(11):6480–6491. doi: 10.1128/IAI.72.11.6480-6491.2004

FIG. 4.

FIG. 4.

Factors affecting secreted anti-CfaB fecal IgA responses elicited in mice subjected to the DNA priming-Salmonella boosting immunization regimen. (A) Nature of the bacterial carrier given to pRECFA-primed mice. Mice were boosted p.o. with live (▪, pRECFA + HG3) or ethanol-inactivated (+, pRECFA + HG3 k) S. enterica serovar Typhimurium HG3 or with live (⧫, pRECFA + ETEC) or ethanol-inactivated (*, pRECFA + ETEC k) ETEC 258909-3. As a control, CfaB-specific fecal IgA titers for a mouse group that was immunized with two doses of pRECFA are indicated (▴, pRECFA). (B) Age-dependent CfaB-specific antibody responses elicited in mice who were first immunized with pRECFA at an age of 1 week (▴, young), 6 weeks (▪, adult), or 52 weeks (⧫, old) and then boosted with two doses of the HG3 strain given 2 weeks apart (pRECFA + HG3). As controls, age-matched mouse groups (pRECFA) were immunized with two i.m. doses (100 μg/dose) of pRECFA, as indicated by the open symbols. (C) Interval between the last priming dose with pRECFA and the first oral booster with the CfaB-expressing HG3 strain. CfaB-specific fecal IgA levels detected in mouse groups that were subjected to intervals of 2 (▴), 4 (▪), 8 (+), 16 (⧫), and 52 (*) weeks are indicated. (D) Amount of DNA required to prime CfaB-specific fecal IgA responses in mice receiving oral boosters with the HG3 strain. The amount of DNA inoculated in each dose was 100 μg (▴), 50 μg (▪), 10 μg (+), or 1 μg (⧫). Experiments were performed with pools of fecal extract collected from different immunization groups. The results shown are based on a representative experiment and are expressed as A492 values for twofold serial dilutions. Statistically significant results (P > 0.05) with regard to mouse groups primed with pRE4 and boosted with the HG3 strain at the lowest tested dilutions were obtained for the following groups: A, pRECFA + HG3; B, pRECFA + HG3 adult and pRECFA + HG3 young; C, all groups except the one with an interval of 52 weeks; D, mouse groups that were immunized with 100 or 50 μg of pRECFA.