Characterization of a Novel Salivary Immunosuppressive Protein from <i>Ixodes ricinus</i> Ticks

In tick salivary glands, several genes are induced during the feeding process, leading to the expression of new proteins. These proteins are typically secreted in tick saliva and are potentially involved in the modulation of the host immune and hemostatic responses. In a previous study, the construction and the analysis of a subtractive library led to the identification of <i><u>I</u>xodes <u>r</u>icinus</i> <u>i</u>mmuno<u>s</u>uppressor (Iris), a novel protein, differentially expressed in <i>I. ricinus</i> salivary glands during the blood meal. In the present study, the data strongly suggest that this protein is secreted by tick salivary glands into the saliva. In addition, Iris is also found to modulate T lymphocyte and macrophage responsiveness by inducing a Th2 type response and by inhibiting the production of pro-inflammatory cytokines. In conclusion, these results suggest that Iris is an immunosuppressor, which might play an important role in the modulation of host immune response.