PpSP32, Phlebotomus papatasi immunodominant salivary protein, exerts immunomodulatory effects on human monocytes, macrophages and lymphocytes

Abstract

AbstractBackground:The saliva of sand flies, vectors ofLeishmaniaparasites,contains several components that exert pharmacological activities facilitating the acquisition of blood by the insect and contribute to the establishment of the infection.Previously, we demonstrated that PpSP32 is the immunodominant salivary antigen in humans exposed toPhlebotomus papatasibites and validated its usefulness as a predictive biomarker of the disease.PpSP32, whose functions are little known to date, is an intriguing protein due to its involvement in the etiopathogenesis of pemphigus, an auto-immune disease. Herein, we aimed to better decipher its role through the screening of several immunomodulatory activities either on lymphocytes or on monocytes/macrophages.Methods:Peripheral mononuclear cells from healthy volunteers were stimulated with anti-CD3 / anti-CD28 antibodies, phytohemagglutinin, phorbol 12-myristate13-acetate / Ionomycin or lipopolysaccharide in the presence of increasing doses of PpSP32. Cell proliferation was measured after the addition of tritiated thymidine. Monocyte activation was tested by analyzing the expression of CD86 and HLA-DR molecules by flow cytometry. Cytokine production was analyzed in culture supernatants by ELISA. THP-1 derived macrophages were stimulated with LPS in the presence of increasing doses of PpSP32 and cytokine production was analyzed in culture supernatants by ELISA and multiplex technique. The effect of PpSP32 onNF-kB signaling was tested by Western blot. The anti-inflammatory activity of PpSP32 was assessedin vivoin an experimental inflammatory model, the carrageenan-induced paw edema in rats.Results:Our data showed that PpSP32 down-modulated the expression of activation markers in LPS-stimulated monocytes and THP1-derived macrophages. This protein negatively modulated the secretion of Th1 and Th2 cytokines by human lymphocytes as well as pro-inflammatory cytokines by monocytes, and THP1-derived macrophages. PpSP32 treatment led to a dose-dependent reduction of theIκB phosphorylation. When PpSP32 was injected into the paw of carrageenan-injected rats, edema was significantly reduced.Conclusions:Our data indicatesthat PpSP32 induces a potent immunomodulatory effect on monocytes and THP-1 derived macrophages. This inhibition could be mediated, among others, by the modulation of the NF-kB signaling pathway. The anti-inflammatory activity of PpSP32 was confirmedin vivoin the carrageenan-induced paw edema model in rats.