Characterization of human T lymphocyte-mediated immune responses induced by a vaccine against American tegumentary leishmaniasis.

Forty-three Brazilians were immunized against American tegumentary leishmaniasis using a vaccine made of whole antigens from killed promastigotes of five American dermotropic Leishmania strains. None of the immunized subjects had a positive reaction in the Montenegro skin test (leishmanin) before vaccination, and 74% developed positive reactions in the skin test after vaccination. The proliferative responses of peripheral blood mononuclear cells (PBMC) induced by antigens from dermotropic Leishmania species were significantly higher after vaccination than before vaccination. However, with antigens from L. chagasi (a causative agent of American visceral leishmaniasis), there was no significant difference between the proliferative responses obtained before and after vaccination. Interferon-gamma was detected in the supernatants of L. braziliensis antigen-stimulated PBMC cultures after vaccination (but not before vaccination). One year after vaccination, PBMC were obtained from eight of the immunized individuals and stimulated with L. braziliensis antigens in proliferative response assays. In all cases, the majority of the responding cells were CD8+ T cells, in contrast to the results of a group of patients with active lesions of tegumentary leishmaniasis, whose L. braziliensis-reactive cells were mainly of the CD4+ T cell phenotype.