[Studies on mechanism of protective immunity against infection of Schistosoma japonicum induced by Sj26 gene transfected dendritic cell].

OBJECTIVE

To explore the mechanism of protective immunity against Schistosoma japonicum infection induced by Sj26 gene transfected dendritic cell (DC).

METHODS

48 BALB/c mice were divided randomly into 4 groups with 12 each. The mice were injected through auricle for three times with Sj26 gene transfected DC (Group A), pcDNA3 transfected DC (Group B), untreated DC (Group C) and RPMI-1640 (Group D) respectively, and challenged with 40+/-2 cercariae of S. japonicum per mouse 2 weeks after the last immunization. Sera from mice were examined for IgG antibody, IFN-gamma and IL-4 by ELISA. Western blot was used for detecting specific anti-Sj26 IgG antibody. The production of IFN-gamma and IL-4 in the supernatant of spleen cells stimulated with soluble egg antigen (SEA) and ConA was quantified by sandwich ABC-ELISA. The proliferation of spleen cells were measured with MTT method.

RESULTS

IgG antibody increased significantly in the mice of group A at 2 weeks after the last immunization (absorbency A491=0.117), higher than that of group B (A491=0.061) and group C (A491=0.058) (P<0.05). The Mr 26000 antigen of S. japonicum was strongly recognized by sera from group A by Western blot. The level of IL-4 in mice of each group showed no significant difference before and after immunization. The level of IFN-gamma in group A (101.4+/-4.9 pg/ml) was significantly higher than that before immunization (15.0+/-1.9 pg/ml) and that of group B (40.1+/-3.1 pg/ml) and group C (35.6+/-1.2 pg/ml) (P<0.01). The level of IFN-gamma in spleen cells from group A in response to ConA and SEA (171.2 and 70.8 pg/ml, respectively) was higher than that of group D (91 and 49.7 pg/ml, respectively) (P<0.01). The level of IL-4 in spleen cells from group A in response to ConA and SEA (79.7 and 50.7 pg/ml, respectively) was lower than that of group D (125.2 and 70.5 pg/ml, respectively) (P<0.01). The stimulating index of spleen cells from group A was 4.1 and 2.82 in response to ConA and SEA respectively, higher than that of other groups (compared with group D, P<0.05).

CONCLUSION

Sj26 gene transfected dendritic cell induces predominant Th1 type immune response which might play a role in protection against S. japonicum infection.