FIG. 3.

Depletion of CD8⁺ or CD4⁺ T cells abolished the protective immunity elicited by pTSSA immunization. C57BL/6 mice were i.m. injected with 100 μg of pTSSA dissolved in 50 μl of PBS into the right hind leg quadriceps four times every 10 days. These mice were i.p. injected with 1 mg of control rat IgG (•), anti-CD8 MAb (▿), or anti-CD4 MAb (□) for three consecutive days until the day of challenge infection. As a control, mice were immunized with empty pCMV vector and treated with 1 mg of control rat IgG (○). Four mice in each group were challenged with 5,000 T. cruzi blood-form trypomastigotes 20 days after the last immunization. The number of parasites in 5 μl of peripheral blood (parasitemia) was determined periodically (A), and survival was monitored daily (B). ✽, P < 0.05 compared to pCMV-immunized, rat IgG-treated mice; ✽✽, P < 0.01 compared to pCMV-immunized, rat IgG-treated mice. The percent survival of pTSSA-immunized, rat IgG-treated C57BL/6 mice was significantly different from that of pCMV-immunized, rat IgG-treated mice (P < 0.05).