Control of Leishmania infantum infection is associated with CD8(+) and gamma interferon- and interleukin-5-producing CD4(+) antigen-specific T cells

Visceral leishmaniasis is a severe and lethal disease caused by the protozo an parasites of the genus Leishmania, In areas where leishmaniasis is endem ic, most infected individuals control the infection and remain asymptomatic ; chemotherapy of visceral leishmaniasis restores some immunity which prote cts against relapses. In the present study, Leishmania-specific T-cell clon es were established from six asymptomatic and five cured patients. Cytokine s production by these clones was analyzed. A large fraction of the parasite -specific T-cell clones from asymptomatic patients were CD8(+) and produced high amounts of gamma interferon (IFN-gamma), Most CD4(+) T-cell clones fr om two asymptomatic subjects exhibited an unusual phenotype: production of high levels of IFN-gamma low levels of interleukin-4, (IL-4), but high leve ls of IL-5. In contrast, only few parasite-specific CD8(+) T-cell clones we re obtained from cured patients after chemotherapy; moreover, CD4(+) T-cell clones from these patients exhibited an heterogeneous profile of cytokines from Th1-like to Th2-like phenotypes, These results point to CD8(+) T cell s and to IL-5- and IFN-gamma-producing CD4(+) T cells as possible contribut ors to human resistance to Leishmania infection. They should stimulate new immunological approaches in the control of this disease.