Oral administration of a Bacillus subtilis spore-based vaccine expressing Clonorchis sinensis tegumental protein 22.3 kDa confers protection against Clonorchis sinensis.

Human clonorchiasis, caused by the infection of Clonorchis sinensis, is endemic in China. In this study, a full-length cDNA sequence encoding C. sinensis tegumental protein 22.3 kDa (CsTP22.3) was identified from adult cDNA library. Recombinant CsTP22.3 was expressed and purified from Escherichia coli BL21. CsTP22.3 was immunolocalized at the tegument of adult C. sinensis by using anti-recombinant CsTP22.3 sera. ELISA was performed using rCsTP22.3 protein to investigate the IgG response to CsTP22.3. Sera from clonorchiasis patients had clear IgG response to CsTP22.3. We used the CotC, a major component of the Bacillus subtilis spore coat, as a fusion partner for the expression of C. sinensis TP22.3 on the spore coat. Western blotting and immunofluorescence analyses were used to identify TP22.3 surface expression on spores. Recombinant spores displaying the TP22.3 antigen were used for oral immunization and were shown to generate mucosal response in rats. TP22.3-specific secretory IgA in faeces reached significant levels 2 weeks after oral dosing. In addition, the recombinant spores induced a significant level of protection (44.7%, p<0.05) in rats challenged with C. sinensis metacercariae. This report shows that C. sinensis TP22.3 expressed on B. subtilis spores was immunogenic and oral administration of TP22.3 spore can provide protection against C. sinensis.