Schistosoma japonicum : screening of cercariae cDNA library by specific single-chain antibody against SIEA26-28 ku and immunization experiment of the recombinant plasmids containing the selected genes

To obtain the gene encoding SIEA26-28 ku, which has been proven to be a potential anti-schistosomiasis vaccine candidate, screening Schistosoma japonicum ( Sj ) cercariae cDNA library with soluble specific single-chain antibody (SIEA26-28 ku-scFv) was performed. A large amount of specific single-chain antibody was harvested through construction of recombinant expression vector pET32a/scFv. The protein was purified and characterized. By using this protein (PET32a-scFv) as a probe, S. japonicum cercariae cDNA library was screened. Two strong positive clones were selected, and their eukaryotic recombinant plasmids were constructed. These genes were named as S. japonicum ribosomal protein S4 ( Sj RPS4) and S. japonicum ribosomal protein L7 ( Sj RPL7), respectively. Experiments of mice showed that both Sj RPS4 and Sj RPL7 DNA vaccines could induce significant immunoprotection. Result of these experiments further proved that the specific single-chain antibody is a very valuable tool in screening of cDNA library to get the corresponding molecules.