Heterologous expression of Schistosoma japanicum signal protein 14-3-3 in Pichia pastoris and the subsequent immune response in mice

Abstract

Schistosomiasis japonica, a zoonosis caused by Schistosoma japonicum, is endemic to the Philippines and China. Several vaccine candidates have been identified and tested in different animal models, but it is still unclear which will be optimal for testing in the field. Therefore, new antigens and strategies are necessary for vaccine development against schistosomiasis japonica. The Sj14-3-3 gene was amplified and subcloned into the expression vector pPICZα-B and transformed into P. pastoris X-33 by electroporation. Three transformants were induced with methanol. The cultural supernatant was collected and tested by SDS-PAGE and Western blotting. The protein of rSj14-3-3 was prepared and purified and BALB/c mice were immunized which was followed by a challenging infection. The immuno-protection was then evaluated. The Sj14-3-3 gene was expressed and secreted into the medium and its molecular weight was about 35000 as determined by SDS-PAGE. Western blotting showed that the protein had a high specificity against mouse-anti-Sj14-3-3 monoclonal antibody and rSj14-3-3 had a promising immune reactivity. The results of the immuno-protective experiments revealed that the worm reduction was 26.0%, 32.2%, and 36.8%, respectively. The number of eggs in liver tissue was reduced by 36.8%, 43.2%, and 46.1%, respectively. The recombinant Sj14-3-3 of eukaryotic expression in Pichia pastoris was successfully harvested. The molecular vaccine of Sj14-3-3 could partially induce resistance to the infection with S. japonicum in BALB/c mice. The recombinant protein Sj14-3-3 has promising immunological potentials for further approach to the diagnosis and development of molecular vaccine.