Common protective effects of the F3 vaccine against the infections by L. chagasi (34) and L. amazonensis also include the increase of: DTH response, TNF-α expression over that of IFN-γ, levels of CD4+ and CD8+ NH36-specific splenocytes, and the impairment of the protective efficacy by depletion of the CD4+ T cells (34), which indicate that cross-protection is mediated by a TH1 response induced against CD4+ epitopes of F3. Here, CD4 is linked to infection.