Objective: To investigate the protective immunity of the recombinant thioredoxin of Schistosoma japonicum(reSjcTrx)in mice.
Methods: Thirty 6-week old female C57BL/6 mice were randomly divided into 3 groups with 10 each: reSjcTrx with Montanide ISA720 adjuvant, adjuvant control, and infection control. Mice were vaccinated subcutaneously at week 0, 2, 4 with reSjcTrx emulsified in Montanide ISA720 adjuvant. The mice in adjuvant group was injected three times with Montanide ISA720 and saline only. Mice in infection control group were given no injection. Three weeks after final injection, each mouse was challenged with 30 +/- 1 cercariae of S. japonicum (Chinese strain). At the week six after challenge, all mice were sacrificed and perfused. The number of recovered worms and eggs from liver tissue of mice were counted. Sera were collected from mice before immunization, before challenge and before killing. The anti-SjcTrx antibodies in sera were detected with ELISA.
Results: ELISA showed a high level of specific IgG antibodies in mice immunized with the reSjcTrx. The worm reduction rate and egg reduction rate of reSjcTrx immunization group were 22.8% and 29.5% respectively, significantly higher than those of the control groups (P < 0.05). SDS-PAGE and Western blotting revealed that the molecular weight of expressed protein was around Mr 14 000 and could be recognized by sera from rabbit infected with S. japonicum and from mice immunized with reSjcTrx.
Conclusion: The reSjcTrx induces certain protective immunity against schistosomiasis japonica in mice.