FIG. 2.

CFA/I-specific IgG subclass responses of BALB/c mice orally immunized with the HG3 strain. Dashed bars indicate IgG1 titers, and open bars indicate the IgG2a titers. Determined IgG1/IgG2a ratios are indicated by filled triangles. Mice were immunized with three doses of CFA/I-expressing HG3 cells (HG3/IPTG), three doses of CFA/I-expressing HG3 cells plus LT_(R192G) (HG3/IPTG/LT 3×), or four doses of CFA/I-expressing HG3 cells plus LT_(R192G) (HG3/IPTG/LT 4×). Results based on immunization carried out with orally administered CFA/I-expressing HG3 cells were based only on mice with a positive response in the IgG-ELISA analyses. Other results were based on pools of serum harvested from the different groups of vaccinated mice. Titers are reported as the means of two independent measurements.