252 The Parasite Echinococcus Granulosus Promotes Allergic Response in Human

BACKGROUND: Helminth parasites are highly antigenic and some types favour the generation or exacerbation of allergic responses by inducing strong Th2-type responses (with the production of cytokines, particularly IL-4). Moreover, recent data suggest that Arginase is involved in the pathogenesis of multiple aspects of allergic disease. In the present work, our aim is to study whether the parasite Echinococcus granulosus induces Th2-type response and whether this is beneficial for the host or not. Echinococcus g. infection, which induces hydatidosis, remains a serious parasitic disease in Algeria. In human, the larval form develops into large cysts especially in the liver and lungs. METHODS: We have investigated the effect of laminated-layer (accelullar layer of hydatic cyst) extract (LLs) on IL-4, and IFN-γ production and Arginase activity in culture performed with mononuclear cells (PBMC). These cells are prepared from peripheral blood of hydatic patients (before and after surgery) and healthy donors. Of note, IFN-γ (Th1 cytokine) downregulates Th2-derived cytokines (like IL-4) which are the best inducer of Arginase pathway. Finally, we have investigated the effects of LLs and IL-4 on protoscoleces (larval form of parasite) viability in PBMC-protoscoleces coculture. RESULTS: We have found that LLs enhanced IL-4 production and Arginase activity and reduced IFN-γ production by PBMC. Furthermore, LLs and IL-4 also enhanced parasite survival in PBMC-Parasite cocultures. Moreover, we have purified by chromatography one of the major antigenic protein in LLs: the fraction 4 (F4, 12kDa). This fraction has the same effect as LLs on Th1/Th2 balance. Interestingly, similar findings are observed in cultures and cocultures performed with PBMC of presurgical and postsurgical patient and healthy donors. CONCLUSIONS: Taken together, our results suggest that the laminated layer of Echinococcus g. may promote allergic response in humans directly by inducting the Th2 pathway. Moreover, this response allows the parasite survival.