FIG. 3.

Protection rates after sporozoite challenge of vaccinated BALB/c WT (▪) and Vα14iNKT-cell-deficient Jα18^−/− (□) mice. (A) Challenge 10 days after F/M immunization or infection of nonimmunized control BALB/c WT (•) and Jα18^−/− (○) mice by intravenous injection of 1,000 live sporozoites (n = 15 [▪], 17 [□], 8 [•], or 6 [○]). CIs significant for comparison of immunized versus control mice were as follows: WT mice (39.2 to 92.5%) and Jα18^−/− mice (30.8 to 90.4%). (B) Challenge 20 days after immunization. Data were pooled from two experiments (n = 6 [▪], 7 [□], 6 [•], or 9 [○]). The CI values were significant only for immunized versus control Jα18^−/− mice (2.5 to 75%). (C) Rechallenge of some of the mice, which were protected in panel A, at day 40 postimmunization (n = 10 [▪], 9 [□], 4 [•], or 3 [○]); there was a significant difference between vaccinated animals and nine pooled KO controls (5.1 to 73.3%). Parasitemia was monitored by peripheral blood films; protected mice were negative on day 13.