The saliva of many vector arthropod species contains factors that inhibit hemostatic responses in their vertebrate hosts. However, less is known about the effect of vector saliva on the development of immune responses. We investigated the effect of Aedes aegypti salivary gland extracts on proliferation and cytokine production by BALB/c mouse splenocytes in vitro. Concanavalin A-mediated T-cell proliferation was markedly inhibited in a dose-dependent manner; inhibition was greater than 50% at 0.12 salivary gland pair (SGP) equivalents. LPS-stimulated B-cell proliferation was also inhibited, although the effect was not as pronounced as for T-cells at low SGP levels. Both cell types were completely suppressed by 0.8 SGP. The production of both TH1-type cytokines (Interleukin-2 [IL-2] and Interferon-gamma) and TH2-type cytokines (IL-4, IL-10, IL-13) was strongly reduced by salivary extract, with 50% or greater inhibition at only 0.03 SGP. Titers of all these cytokines were reduced by 70-99% even at very low SGP levels that did not inhibit proliferation. In contrast, titers of the macrophage-derived cytokine IL-12 are reduced only at relatively high SGP levels. Although IL-12 is an important mediator of TH1 responses, the effect of A. aegypti saliva on TH1 responses is not dependent on reduced IL-12 titers. Taken together, these results support the hypothesis that A. aegypti saliva may exert a marked immunomodulatory influence on the environment at the bite site. This immunomodulation is likely to have profound consequences for pathogens and parasites transmitted by this mosquito.
Species 1: Diptera Culicidae Aedes aegypti
Keywords: Immunomodulation, TH1/TH2
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