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

FIG. 5.

FIG. 5.

Activation of Th1-type responses in mice subjected to the primer-booster immunization regimen. (A) Determination of anti-CfaB IgG1 (white bars) and IgG2a (black bars) subclasses in serum samples collected from mice who were immunized only with pRECFA (pRECFA) or the CfaB-expressing HG3 strain (HG3), primed with pRE4 and boosted with the HG3 strain (pRE4 + HG3), or subjected to the complete primer-booster regimen (pRECFA + HG3). (B) Determination of IFN-γ (black bars) and IL-4 (white bars) production in spleen homogenates harvested from mice who were immunized only with pRECFA (pRECFA) or the CfaB-expressing HG3 strain (HG3), primed with pRE4 and boosted with the HG3 strain (pRE4 + HG3), or subjected to the complete primer-booster regimen (pRECFA + HG3). Cell cultures were stimulated with 25 μg of purified heat-denatured CFA/I fimbriae/ml. IgG subclass (two determinations) and cytokine (one determination) detection values are represented by end-point reverse titers ± SE and mean nanograms per milliliter ± SE, respectively. *, statistically different values (P < 0.05) compared to results obtained with pRECFA-vaccinated mouse groups.