FIG. 2.

Humoral immune responses stimulated by the SfbI derivatives. Mice (n = 5) were intranasally immunized with 510 pmol of the corresponding polypeptide together with 180 pmol of CTB. (A) Kinetics of the fragment-specific serum IgG responses. Results are expressed as the reciprocal log₂ of the geometric mean endpoint titer (GMT) of five mice per group; immunizations are indicated by arrows. The obtained results are statistically significant (Student's t test) when compared with values for the control group (CTB alone) at P < 0.05 (∗). The standard errors of the mean (SEM) were in all cases lower than 5% of the values. (B) Isotype profiles of the antigen-specific IgG antibodies present in the serum of vaccinated mice. Results are the averages of triplicate samples. SEM are indicated by vertical lines. (C) Antigen-specific IgA antibodies in lung washes of mice. Results are expressed as the percent antigen-specific IgA antibodies with respect to total IgA. The obtained results are statistically significant when compared with values for the control group (CTB alone) at P < 0.05 (∗). SEM are indicated by vertical lines.