FIG. 5.

Induction of TT-specific serum IgG, IgM, and IgA antibody responses by coadministered Stx1 derivatives (A) and protection against fatal challenge with tetanus toxin (B). Mice were subcutaneously immunized with TT plus mStx1, nStx1, or StxB1. Specifically, C57BL/6 mice were subcutaneously immunized with 100 μl of TT plus 1 μg of Stx1 mutant (E167R/R170L; mStx1) or 1 μg of StxB1 (hatched bars), 10 μg of Stx1 mutant or 10 μg of StxB1 (dotted bars), or 25 μg of Stx1 mutant or 25 μg of StxB1 (black bars) as an adjuvant or with TT alone (white bars) on days 0 and 14. Serum samples were collected on day 21 and examined for TT-specific Ab responses by ELISA. One week after the last immunization, mice were challenged on day 21 by the subcutaneous injection of 130 LD₅₀s of tetanus toxin in 0.5 ml of PBS including 0.2% gelatin. *, P < 0.05 compared with mice immunized with OVA alone. The results are expressed as means ± SEM from a total of three separate experiments, each of which used five or six mice per group.