Cs RNASET2 is an important component of Clonorchis sinensis responsible for eliciting Th2 immune response

Many parasites can trigger the host immune response by releasing excretory/secretory proteins (ESPs). Cs RNASET2, a glycosylated T2 ribonuclease present in ESPs of Clonorchis sinensis ( C. sinensis , Cs ), has recently been reported to possess potent effects in regulating mouse dendritic cells (DCs). However, it is unclear whether Cs RNASET2 can induce adaptive immune response. In this study, we carried out further investigations on biochemical features of Cs RNASET2. Besides, we immunized Balb/c mice with Cs RNASET2 and orally infected Balb/c mice with C. sinensis , respectively. Sera of immunized mice were collected and evaluated for specific antibody titers by ELISA. Splenocytes of experimental mice were isolated and stimulated in vitro. The expression levels of IL-4 and IFN-γ in splenocytes of immunized mice and infected mice were detected by ELISA and flow cytometry. Our results showed that the sequence of Cs RNASET2 had close relationship with the homologue from Echinococcus multilocularis . The conserved active site (CAS) motifs, active histidine residues, and N-linked glycosylation region of Cs RNASET2 were close to each other in the three-dimensional structure. In addition, sera of Cs RNASET2 immunized mice had obviously higher levels of specific antibody titers. Splenocytes from both Cs RNASET2 immunized mice and C. sinensis infected mice expressed increased levels of IL-4, while the production of IFN-γ exhibited no significant difference. Immunization with Cs RNASET2 elicited Th2 immune response by promoting the synthesis of IL-4, consistent with the immune response initiated by infection of C. sinensis . Taken together, these data suggested that Cs RNASET2 was important for C. sinensis to trigger Th2 immune response.