Figure 3.

Pre-infection with Leishmania braziliensis (Lb) can cross-protect mice against L. amazonensis (La) infection. C57BL/6 mice (five per group) were infected with 2 × 10⁶ Lb promastigotes in the left hind foot. After the healing of the primary infection at 8 weeks (short-term) or 24 weeks (long-term), some mice and their age-matched controls were given 2 × 10⁶ La promastigotes in the right hind foot. (a) Lesion sizes (mm) were monitored weekly for an additional 8 weeks following La infection. (B) Parasite loads in La-infected foot were determined at 8 weeks post-infection using a limiting dilution assay. **P < 0.01 (by Kruskal–Wallis test) indicates statistical significances among these three groups. (c) Lb-exposed mice (infected and healed at 8 weeks) as well as age-matched controls were given 2′ 10⁶ La promastigotes in the right hind foot. One week later, draining LN cells were collected and pooled into two sample sets. The percentages of IFN-γ production from indicated Vβ⁺ CD4⁺ T cells were measured. Shown are representative results from four repeats with similar trend.