Visceral leishmaniasis : activation of human T-lymphocytes by two specific Leishmania antigens

T cell responses to a specific Leishmania antigens, 70kD and 116kD were investigated in individuals from an endemic area for leishmaniasis. Peripheral blood mononuclear cells were obtained from 38 individuals (24 test an d14 controls) and T cell responses to phytohaemaglutinin (PHA), Concanavalin A (ConA) and the specific Leishmania antigens were examined. PHA and Con A-induced responses were all positive in both the test and control groups. Eighteen out of 24 individuals with previous history of visceral leishmaniasis and 12 out of 14 normal individuals residing in the endemic areas responded to the 70kD antigen. In contrast, all the eight normal individuals all the eight normal individuals from a non-endemic area for leishmaniasis did not responded, indicating that cellular responses to the 70kD antigen are specific for Leishmanai spp. The 116kD antigen, on the other hand, exhibited poor specificity: about 30% of the individuals with a previous history of leishmaniasis did not respond to this antigen. A significant proportion of the population from an endemic area, but with no history of visceral leishmaniasis, responded to the 70kD antigen. This is an indicator of a prior exposure to Leishmania parasite and is consistent with previous studies which have shown that subclinical infections of visceral leishmaniasis do occur in such areas. Results from the present study suggest that the 70kD antigen is a strong candidate for vaccine development.