Leishmania infantum released proteins specifically regulate cytokine expression and production patterns by CD4+ and CD8+ T cells.

Specific immune responses by CD4+ and CD8+ T cells, from two infected mice strains (BALB/c and C57BL/6), induced by High, Inter and Low protein fractions released by Leishmania infantum, were assessed through the evaluation of IL-12, IFN-γ and IL-10 mRNA by real-time PCR and respective protein production by ELISA. During infection establishment, High and Inter fractions directed both mice strains T cells subsets to increase the production of IFN-γ, associated to IL-12 release. Later on, parasite replication augmented in BALB/c and stabilised in C57BL/6 mice. Inter fraction induced CD4+ T cells to maintain IFN-γ production, with the simultaneous release of IL-12 by both cell subsets in BALB/c mice and by CD8+ T cells in C57BL/6 mice. These observations suggested a prophylactic potential for Inter fraction which was able to induce Th1 response with IL-12 involvement, required for the maintenance of memory cells, in mice strains with different parasitic evolution.