Immunoregulatory peptides from salivary glands of the horsefly, Tabanus pleskei.

Horseflies are economically important blood-feeding arthropods and vectors for several pathogenic microorganisms. Horseflies rely heavily on pharmacological propriety of their saliva to get blood meal and suppress immune reactions of hosts. Few reports cover immune suppressants from horsefly salivary glands. Three immunoregulatory peptides named immunoregulin TP1-3 have been identified and characterized from salivary glands of the horsefly Tabanus pleskei (Diptera, Tabanidae). Immunoregulin TP1 could inhibit the secretion of interferon-gamma (IFN-gamma), monocyte chemoattractant protein (MCP-1) and increase the secretion of interleukin-10 (IL-10) induced by lipopolysaccharide (LPS) in mouse splenocytes. IL-10 is a suppressor cytokine of T-cell proliferation and cytokine responses. IL-10 can inhibit the elaboration of pro-inflammatory cytokines. In the current studies, Immunoregulin TP1 inhibited the IFN-gamma and MCP-1 secretion possibly by upregulating the IL-10 production, and finally might facilitate the blood-feeding of this horsefly. The current works will help understand the molecular mechanisms of the ectoparasite-host relationship.