[Screening and evaluation of Schistosoma japonicum SjRibosomal_L18a protein and its B cell epitopes].

OBJECTIVE: To screen a ribosomal protein (SjRibosomal_L18a) of Schistosoma japonicum and predict its B cell epitopes, and evaluate the potential diagnostic value of the recombinant protein and the synthetic B cell epitopes. METHOD: S. japonicum protein sequences were screened and analyzed by using B-cell epitope prediction softwares. The immunogenic protein was selected based on the predicted score and the quantity of epitopes. The epitopes with higher score (P1 and P2) were synthesized. The relative molecular mass (M(r)), isoelectric point, grand average of hydropathicity, signal peptide, and transmembrane domain were predicted by bioinformatics tools. RT-PCR was used to analyze the transcription level of the different development stages. The encoding sequence was amplified by PCR, and cloned into pET28a vector. The recombinant plasmid was transformed into in E. coli BL21 (DE3) cells and induced with IPTG. The recombinant SjRibosomal_L18a protein was purified with Ni-NTA resin. ELISA was used to evaluate the potential diagnostic value of the recombined protein and the synthetic B cell epitopes. RESULTS: SjRibosomal_L18a protein was obtained, its B cell epitopes and physicochemical properties were predicted. The open reading frame of SjRibosomal_L18a was composed of 531 bp, and encoded a 176-amino-acid protein with M(r) 20 741, pI 11.12. RT-PCR result showed that this gene was transcribed at high level in each developmental stage. The recombinant plasmid SjRibosomal_L18a/pET-28a was constructed and the protein was expressed as inclusion bodies (M(r) 26069). The sensitivity and specificity of recombined protein, P1 and P2 were 53.3% (8/15) and 100% (15/15), 60% (9/15) and 100% (15/15), 73.3% (11/15) and 100% (15/15), respectively. CONCLUSION: The recombinant protein (SjRibosomal_L18a) and its epitopes with higher immunogenicity are obtained. The sensitivity of the two epitopes (P1 and P2) was higher than that of SjRibosomal_L18a protein.