CHARACTERIZATION OF HUMAN T-LYMPHOCYTE-MEDIATED IMMUNE-RESPONSES INDUCED BY A VACCINE AGAINST AMERICAN TEGUMENTARY LEISHMANIASIS

Forty-three Brazilians were immunized against American tegumentary lei shmaniasis using a vaccine made of whole antigens from killed promasti gotes of five American dermotropic Leishmania strains. None of the imm unized subjects had a positive reaction in the Montenegro skin test (l eishmanin) before vaccination, and 74% developed positive reactions in the skin test after vaccination. The proliferative responses of perip heral blood mononuclear cells (PBMC) induced by antigens from dermotro pic Leishmania species were significantly higher after vaccination tha n before vaccination. However, with antigens from L. chagasi (a causat ive agent of American visceral leishmaniasis), there was no significan t difference between the proliferative responses obtained before and a fter vaccination. Interferon-gamma was detected in the supernatants of L, braziliensis antigen-stimulated PBMC cultures after vaccination (b ut not before vaccination). One year after vaccination, PBMC were obta ined from eight of the immunized individuals and stimulated with L. br aziliensis antigens in proliferative response assays. In all cases, th e majority of the responding cells were CD8+ T cells, in contrast to t he results of a group of patients with active lesions of tegumentary l eishmaniasis, whose L. braziliensis-reactive cells were mainly of the CD4+ T cell phenotype.