Background: Suppression and modulation of the immune response of the host by nematode parasites have been reported widely. Rhodaneses or thiosulfate: cyanide sulfurtransferases are present in a wide range of organisms, such as archea, bacteria, fungi, plants and animals. Previously, it was reported that a rhodanese homology could bind by goat peripheral blood mononuclear cells (PBMCs) in vivo.Results: In the present study, we cloned and produced recombinant rhodanese protein originated from

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... onchus contortus (rHCRD), which was one of the parasitic nematodes of small ruminants. The effect of this protein on modulating the immunity of goat PBMC and monocyte was studied in the current work. The predominant localization of the natural HCRD protein was verified as the bowel wall and body surface of worms, according to the immunohistochemical tests. It was proved in this study that the serum produced by artificially infecting goats with H. contortus successfully recognized rHCRD which conjugated goat PBMCs. The rHCRD was co-incubated with goat PBMCs to observe the immunomodulatory effect on proliferation, apoptosis and secretion of cytokines exerted by HCRD. The results showed that the interaction of rHCRD suppressed proliferation of goat PBMCs stimulated by ConA but did not induce the apoptosis of goat PBMCs. After rHCRD exposure, the production of TNF-α and IFN-γ were significantly decreased, however, it significantly increased the secretion of IL-10 and TGF-β1 in goat PBMCs. Phagocytotic assay by FITC-dextran internalization showed that rHCRD inhibited the phagocytosis of goat monocytes. Moreover, rHCRD could down-regulate the expression of MHC-II on goat monocytes in a dose-dependent manner. Conclusions: These discoveries proposed a possible target as immunomodulator, which was potentially beneficial to illuminate the interaction between parasites and hosts in the molecular level and hunt for innovative protein species as candidate targets of drug and vaccine.