Modulation of murine cellular immune response and cytokine production by salivary gland lysate of three sand fly species.

Saliva of sand flies (Diptera: Phlebotominae) plays an important role in transmission of Leishmania parasites by modulating host immune response. However, because of the different protein compositions of saliva, the immunomodulatory effects may vary among sand fly species. We have therefore analysed and compared the immunomodulation effects of salivary gland lysate (SGL) of three different sand flies. Spleen cells from BALB/c mice were incubated with SGL of Phlebotomus papatasi, P. sergenti or Lutzomyia longipalpis. Concanavalin A-stimulated lymphocyte proliferation was significantly suppressed with SGLs of all three sand fly species and all SGL doses tested. This result indicates that saliva from different sand fly species is able to suppress host proliferative response even to the potent mitogen. In parallel experiments, we analysed the effect of SGL on IFN-gamma, IL-2, and IL-4 production; in mitogen-stimulated cells SGLs markedly inhibited IFN-gamma production in all intervals tested (reduced up to 31%) and to a lesser degree impaired production of the other two cytokines as well. Despite some species-specific differences in the intensity of immunomodulatory effects, saliva of all sand fly species modulated cell proliferation as well as cytokine production in a similar way.