Abstract:

Objective To enhance the immunogenicity of the recombinant pVIVO2-IL12-Sj23 vaccine of Schistosoma japonicum by using mixed vegetal polysaccharides as adjuvant. Methods The plasmid pVIVO2-IL12-Sj23 was constructed. 3 groups of BALB/C mice were injected intramuscularly with normal saline (Group A）, pVIVO2-IL12-Sj23 plasmid DNA (B）, and pVIVO2-IL12-Sj23 plus mixed vegetal polysaccharides (C） respectively, and challenged with S.japonicum cercariae on the 4th week after immunization. Mice were killed to calculate the worm reduction rate and egg reduction rate in liver tissue on the 6th week after infection. Before and 4 weeks after immunization blood samples were collected. Results The worm reduction rate and egg reduction rate were 64.3% and 79.9%, respectively in group C, 45.5% and 58.4%, respectively in group B, showing a remarkable difference between them（P<0.05）. ELISA analysis showed a significantly higher level of IgG specific for Sj23 4 weeks after vaccination in groups B and C（P<0.05）. However, there was no significant difference in IgG level between groups C and B （P＞0.05）. Conclusion When mixed vegetal polysaccharides are used as adjuvant, the effect of the vaccine pVIVO2-IL12-Sj23 can be considerably enhanced.

Key words: Schistosoma japonicum, pVIVO2-IL12-Sj23 vaccine, Tea polysaccharide, Lentinan, Adjuvant