FIG. 5.
(A) Long-term antibody and memory responses in mice immunized with wild-type PA, Oligo-, or DNI. Mice were immunized four times as indicated by arrows and sera were obtained seven days after each immunization. After the 3rd immunization and over the course of more than one year, DNI- or Oligo--immunized mice consistently maintained significantly higher levels of anti-PA IgG than mice immunized with wild-type PA. (B) Toxin-neutralizing activities of mouse sera obtained more than one year (day 397) after immunization with wild-type PA, Oligo-, or DNI. Sera from DNI-immunized mice were more active that those from PA-immunized mice. Interestingly, Oligo- induced high amounts of anti-PA (A) but decreased levels of toxin-neutralizing activity (B).