SCREENING OF EPITOPES MIMICKING FEMALE SCHISTOSOMA JAPONICUM ANTIGEN AND THEIR PROTECTIVE IMMUNITY

Objective To obtain peptide mimicking epitopes of female Schistosoma japonicum (Sj) worm through screening of a phage peptide library and to explore their immune protection against Sj in mice. Methods A 12-mers random peptide library was immunoscreened with purified IgG from rabbits' sera immunized with soluble female Sj antigen. After three rounds of biopanning,the pooled phages were used to immunize mice for three times at week 0,2,4. Two weeks after last immunization each mouse was challenged by 40 cercaria, then all mice were perfused after 42 days and the worms and eggs were counted. 18 randomly picked clones were detected by Dot-ELISA,of which 4 positive clones were sequenced. Results The specific phages binding to IgG were enriched 200 folds after three rounds of biopanning. 17 of the 18 randomly picked clones were shown to be antigenic and the 4 sequences of the positive clones showed no homology with other sequences in the GenBank. Compared with control group,a significant reduction in adult worms (26.57%) and a high egg reduction (65.34%) were achieved following immunization. Conclusion The specific peptides simulating antigenic epitopes of female Sj can be obtained by immunoscreening phage random peptide library and a protective immunity against Sj can be induced by these epitopes in mice.