Identification of novel antigens within the Schistosoma japonicum tetraspanin family based on molecular characterization

Tetraspanins (TSPs) are proteins found on the surface of the parasite Schistosoma mansoni that have been regarded as potential protective antigens. However, divergent evolution may occur among the species of S. mansoni and Schistosoma japonicum under different environmental pressure. Thus, it was essential to characterize the S. japonicum TSP family members before selecting potential candidate TSP antigens. In this study, we used bioinformatics and experimental validation to investigate 29 TSP members from S. japonicum, including all known genes, Sj23, TE736, Sj25, and Sj-TSP-2. Five TSP members were found to be variable, and two others (Sj-tsp genes) were alternatively spliced. The phylogenetic analysis showed that schistosome TSPs were highly divergent from those of other phyla. Quantitative RT-PCR revealed that the Sj-tsp genes were differentially transcribed in the developmental stages of cercariae, schistosomula, adult worms, and eggs. Six Sj-tsp genes were significantly up-regulated during the transformation from cercariae to schistosomula. Four Sj-tsp genes, including Sj-tsp-1, Sj-tsp-8, Sj-tsp-14, and Sj-tsp-26 were confirmed as potential protective antigens based on the molecular characterization. RNAi was preformed against the conserved Sj-tsp genes which were highly expressed in schistosomula to explore gene functions. These data will promote the identification of candidate antigens within the TSP family for developing novel vaccines against S. japonicum infections.