[Preliminary studies on protective immunity induced by recombinant protein of Schistosoma japonicum P14 gene and its mechanism against schistosome infection in mice].

OBJECTIVE

To explore the immune protective effect of the basic calponin-like protein (SjP14) in mice response to the infection of Schistosoma japonicum.

METHODS

The recombinant plasmid pET28a(+)-SjP14 was built, and transferred into E. coli BL21 cell line. After induced, by isopropyl-beta-D-thiogalactoside (IPTG), the target protein was purified, and then analyzed by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting, respectively. Thirty female BALB/c mice (six-week age) were randomly divided into three groups (n = 10 for each), including A group (rSjP14 experimental), B group (adjuvant control), and C group (saline control). The mice in the A group were subcutaneously injected with 100 microg rSjP14 vaccine for three times at 2-week interval. After the final immunization, the mice were infected by cercariae of S. japonicum. The B or C groups experienced subcutaneous injections of adjuvant or saline, respectively, except for cercaria infection. The levels of sera IgG, IL-4 and IFN-gamma were detected by ELISA before immunizing, 6 weeks after immunizing, and 6 weeks after the infection, respectively. The reduction rates of worms or eggs were also calculated at the 6th week after the infection.

RESULTS

The SjP14 protein was about 38 kDa and was recognized successfully by polyclonal antibody of SjP14. The level of serum IgG in the A group at the 6th week after the infection of cercariae was significant increased [ (25.52 +/- 1.91) microg/ml] compared with that in the B [ (18.65 +/- 3.16) microg/ml] and C [(22.44 +/- 2.83) mcirog/ml] groups (P < 0.05); the level of serum IFN-gamma [(171.30 +/- 70.12) ng/L] was also increased, compared with that in the B [(136.89 +/- 37.62) ng/L] and C [(153.64 +/- 43.44) ng/L] groups (P < 0.05). However, the level of serum IL-4 [(112.05 +/- 15.02) ng/L] in A group was significant decreased at the 6th week after the infection, compared with that in the C group [(102.82 +/- 27.46) ng/L] (P < 0.05). The reduction rates of worms and eggs in the A group were 29.2% and 41.3%, respectively, after the infection, which had statistically significant differences compared with those of the C group (P < 0.05).

CONCLUSION

SjP14 has a protective immunity against S. japonicum infection in mice.