Prediction And Identification For The Vaccine Candidates Against Schistosoma Japonicum Based On Functional Genomics Data

Schistosomiasis caused by Schistosoma infection is a widely distributed and severely zoonotic parasitic disease and could lead to chronic pathological damage and threaten to human health. The conventional methods for schistosomiasis control include controling infectious sources, blocking transmission, feces management, water conservation as well as the protection of susceptible population. Chemotherapy with praziquantel is the major measures for schistosomiasis control which is expensive and is required for a large number of specialized technical personnel, but it can not prevent both human and animals from reinfection. The resistance for schistosoma to praziquantel is under inspection. Thus, people are still searching for more efficient way to control schistosomiasis prevalence. The research and development of vaccine against schistosomiasis would be the best way to prevent this disease.Many studies have confirmed that, the high levels of protective immunity are induced by a variety of animals immunized with attenuated cercariae at appropriate doses of radiation (including ultraviolet, X-ray and other ray). In the radiation-attenuated cercariae vaccine model, the antigens may be released from schistosomula in lungs and could induce a high level of Thl type CD4+ cell-mediated effects, then memory cell group would keep host from reinfection. Several antigens are identified by the conventional immunological triage techniques, although identification of protective antigens are still under investigation. This is may be because the antigens released in RA model are too many and complicated to be detected. Identification of protective antigens are needed to accelerate vaccine development. In recent years, with the development of theory and technology of schistosome functional genomics, the researchers have provided us a lot of data on schistosoma genome, transcriptome and proteome. Whether the information on protective antigens in RA protection model could be minned from schistosoma functional genomics data metioned above is worthy of being explored as a hot topic in research of schistosome vaccine. Therefore, this study used data mining, reverse vaccinology and other technologies to screening candidate molecules which can simulate the candidate molecules in radiation-attenuated cercariae vaccine model to induce Thl CD4+ cell-mediated immune response in host, and provided foundation for further study on screening out the new protective antigens or epitopes against Schistosoma japonicum.Based on immunologic mechanism of radiation-attenuated vaccine, candidated sequences were selected by BLASTP searching normal Schistosoma japonicum schistosomula's or adult worms'transcriptome and proteome sequences being homologous with the sequences from characteristic transcriptome (Schistosoma mansoni) and proteome (Schistosoma japonicum) of schistosomula transformed from irradiated cercaria; then annotation and analysis of candidated sequences were carried out by using online softwares, databases and scientific documents.131 sequences of Schistosoma japonicum were obtained, which were homologous or consistent with molecular sequences of schistosomula transformed from irradiated cercaria; the analysis of scientific documents indicated that, among the 131 predicated sequences,52 molecules could be designated as candidate antigens for Schistosoma japonicum vaccine, they are of similar sequence features to that of some antigen molecules located in schistosome tegument, or play important roles in the schistosome' s growth, development, migration, and other functions. These results could provide valuble information for the further validation of the potential molecules.Structural protein SJCHGC01894 was selected as further T cell epitope prediction and identification from the 52 vaccine candidates. In this study, the imunoinformatics and other related technologies were also applied. Three servers based on three different methods were chosen to predict Th cell epitope, subsequently, the binding peptides to MHCâ…¡ molecules was further optimized by using docking simulation sever of receptor and ligand based on molecular dynamic algorithm which was designed by ClusPro server. Bias of a single server or algorithm was excluded. The final sequence epitope was NH-MEAFKTFDREGQGFI-COOH [resource sequence:AAW26398.1; similarity to myosin light chain]. In order to identify the epitope, The mice were vaccinated with candidated epitopes which were synthesized artificially (coupled with the poly-lysine skeleton), intracellular cytokines were measuried by 3 colour flow cytometry. Flow cytometry results showed that both groups immunized with predicted epitope and positive epitope peptide demonstrated different differentiation potency before and after stimulation with the same epitopes in vitro. After stimulated with epitope peptide, the ratio of CD4+ cells differentiated to Thl and Th2 cells increased and the proportion of Thl cells was higher than that of Th2 cells, suggesting that CD4+ T cell differentiation caused by epitope peptide immunization was Thl profile.Taken together, a array of protective immune-related vaccine candidate moleculs in schistosome RA protection model were screened by analysis of data on schistosome transcriptome and proteome, and the predicted epitope NH-MEAFKTFDREGQGFI-COOH [Source serial number: AAW26398.1; similarity to myosin light chain] were indentified by combined immunoinformatics theoretical prediction with in vitro experimental validation technology. In this study we explored a novel method for rapid discovery of protective antigens or epitops against schistosomiasis by data-mining based on schistosome functional genomics and reverse vaccinology, and provide basis for further identifying protective antigens or epitopes being in the RA immunization model.