FIG. 2.

In vivo cytotoxic activity against target cells coated with a peptide representing the CD8 epitope in mice immunized with different protocols before or after challenge with T. cruzi. A/Sn mice were injected with the different immunization protocols depicted at the side of the charter. The immunizing doses were injected i.m. at 0 and 3 weeks. Two weeks after the final immunizing dose, half of the mice were injected with splenic syngeneic cells labeled with CFSE and coated with peptide TEWETGQI. The remaining half of the animals was challenged i.p. with 150 blood forms of T. cruzi. Thirteen days later, these mice were also injected with splenic syngeneic cells labeled with CFSE and coated with the peptide TEWETGQI. The specific in vivo cytotoxic activity was estimated after 20 h as described in Materials and Methods. Results are expressed as medians (bars), and each dot represents an individual mouse. Symbols denote significantly higher (P < 0.01) specific in vivo cytotoxic activity compared to control naive or pcDNA-3/Adβ-gal injected mice prior to infection (asterisks) or after a challenge with T. cruzi (crosses). The results are representative of experiments performed twice with similar results.