FIG. 7.

Long-term protective immunization with WT or L16 clone epimastigotes against challenge with virulent T. cruzi Tulahuen. Adult Swiss mice (n = 15) were primed with 10³ CRF of either the L16 clone or the WT strain. Fourteen months later, the mice were challenged, together with naive controls (n = 5), with 10⁴ bloodstream forms of the highly virulent T. cruzi Tulahuen strain. (A) Parasitemia levels periodically measured during 60 days. Note the significant protection (P < 0.001) in L16-preinoculated mice. Values are given as means; error bars indicate standard errors of the means. (B) Spleen indexes on day 65 postchallenge. Note the significant protective effect of the genetically altered parasites (P < 0.002). A representative experiment of three independent assays is shown.