Molecular characterization and immune modulation properties of Clonorchis sinensis-derived RNASET2

Clonorchis sinensis (C. sinensis, Cs) is a trematode parasite that often causes chronic cumulative infections in the hepatobiliary ducts of the host and can lead to pathological changes by continuously released excretory/secretory proteins (ESPs). A T2 ribonuclease in trematode ESPs, has been identified as a potent regulator of dendritic cell (DCs) modulation. We wondered whether there was a counterpart present in CsESPs with similar activity. To gain a better understanding of CsESPs associated immune responses, we identified and characterized RNASET2 of C. sinensis (CsRNASET2) in this paper.

We expressed CsRNASET2 in Pichia pastoris and identified its molecular characteristics using bioinformatic analysis and experimental approaches. The immune modulation activities of CsRNASET2 were confirmed by evaluating cytokine production and surface markers of recombinant CsRNASET2 (rCsRNASET2) co-cultured DCs, and monitoring levels of IgG isotypes from rCsRNASET2 administered BALB/c mice.

CsRNASET2 appeared to be a glycoprotein of T2 ribonuclease family harboring conserved CAS motifs and rich in B-cell epitopes. Furthermore, CsRNASET2 was present in CsESPs and was able to modulate cytokine production of DCs. In addition, rCsRNASET2 could significantly suppress the expression of lipopolysaccharide-induced DCs maturation markers. In addition, when subcutaneously administered with rCsRNASET2 there was a marked effect on IgG isotypes in mouse sera.

Collectively, we revealed that CsRNASET2, a T2 ribonuclease present in CsESPs, could modulate DCs maturation and might play an important role in C. sinensis associated immune regulation in the host.