Serodiagnostic applicability of recombinant antigens of Clonorchis sinensis expressed by wheat germ cell-free protein synthesis system

We evaluated the diagnostic applicability of recombinant proteins from Clonorchis sinensis, the human liver fluke. Four recombinant proteins, 7-kDa protein (Cs7P), 28-kDa cysteine protease (Cs28CP), and 26- and 28-kDa glutathione s-transferases (Cs26GST and Cs28GST), were expressed by wheat germ cell-free protein synthesis system. In ELISA, crude antigen showed the highest sensitivity (92.7%). However, sensitivities of r7P (47.3%), r28CP (30.9%), r26GST (21.8%), and r28GST (14.5%) were dramatically lower. The overall specificities of the crude antigen, r7P, r28CP, r26GST, and r28GST, were 100%, 94.5%, 96.7%, 94.5%, and 98.9%, respectively. Taken together, r7P and r28CP showed moderate sensitivities and high specificities, whereas r26GST and r28GST revealed low sensitivities and high specificities. We demonstrated that recombinant antigens, when used as a single antigen for ELISA, are not sensitive enough to diagnose clonorchiasis. Cocktail or chimeric antigens may be useful to increase the sensitivity of each antigen and may improve the serodiagnosis of clonorchiasis.