The protective immunity of a DNA vaccine encoding Schistosoma japonicum Chinese strain triose-phosphate isomerase in infected BALB/C mice.

The development of a DNA vaccine for schistosomiasis japonica and testing the protective efficacy after challenge in BALB/c mice were performed. Thirty-nine female BALB/c mice were divided into three groups. Each mouse of the control group was injected intramuscularly with 100 microg of pcDNA3.1 DNA. In the TPI group, each mouse was injected with 100 microg of pcDNA3.1-SjCTPI DNA. The TPI+IL-12 group was injected with 100 microg of pcDNA3.1-SjCTPI DNA and 100 microg of the mixture of pcDNA3.1-P35 and pcDNA3.1-P40 DNA. Each mouse was immunized three times at two-week intervals and challenged with 45 cercariae of Schistosoma japonicum Chinese strain four weeks post-immunization. Then the mice were sacrificed and perfused at 45 days after challenge; the recovered worms and hepatic eggs were counted. Cytotoxic T lymphocyte (CTL) activity mediated by SjCTPI was detected with the 51Cr release assay. ELISA was performed for the detection of anti-rTPI antibodies. Anti-rTPI antibody detection with ELISA after immunization showed ten serum samples from the control group were negative, five of ten serum samples from the TPI group were weakly positive, six of ten from the TPI+IL-12 group were also weakly positive. The CTL activity of the control group was 9.1%, while CTL activities of the TPI group and the TPI+IL-12 group were 27.6% and 54.4%, respectively. The worm and egg reduction rates of TPI group and the TPI+IL-12 group were 30.2%, 52.9%, 32.7%, and 47.0%, respectively in comparison with the control group. This study further proved the possibility of the SjCTPI DNA vaccine as a potential DNA vaccine for schistosomiasis.

Protective immunity induced with 23 kDa membrane protein dna vaccine of Schistosoma japonicum Chinese strain in infected C57BL/6 mice.

A 23 kDa membrane protein DNA vaccine for Schistosoma japonicum Chinese strain was developed and tested for its protective efficacy and immune responses in infected C57BL/6 mice. The cDNA encoding SjC23 amplified from pUC19-SjC23 were subcloned into an eukaryotic expression vector (pcDNA3.1). Forty-eight female C57BL/6 mice were divided into three groups. Each mouse of group A (control group) was immunized intramuscularly (i.m.) with 100 microg of pcDNA3.1; of group B (SjC23 group) was immunized (i.m.) with 100 microg of pcDNA3.1-SjC23; of group C (SjC23+IL-12) was immunized (i.m.) with a mixture of 100 microg of pcDNA3.1-SjC23, 100 microg of pcDNA3.1-p35 and 100 microg of pcDNA-p40. These were followed by two boosts of the same DNA once every two weeks. All mice were challenged with 45 cercariae of Schistosoma japonicum Chinese strain at week 8, and were killed and perfused at week 14. The numbers of recovered worms and hepatic eggs were counted. The expression of SjC23 and p35, p40 in muscle tissue was determined by immunohistochemical method. By culture of spleen cells, the production of IL-2, IL-4, IL-10 and IFN-gamma with the stimulation of specific antigen of the recombinant hydrophilic domain of SjC23 (rSjC23-HD) was determined after the last immunization (before challenge). Sera were collected from each group before immunization and two weeks before and after challenge. Anti-SjC23 antibodies were tested by Western blot. The results showed that SjC23 and p35, p40 of mouse IL-12 were expressed on the membrane and in the plasma of the muscle cells of immunized C57BL/6 mice. A rise of IL-2 and IFN-gamma in the SjC23 group and SjC23+IL-12 group was observed; No changes were found in IL-4 and IL-10. Detection of anti-SjC23 antibody with Western blot showed that after the third immunization (before challenge) all the serum samples from the control group were negative; 8 of 10 sera from the SjC23 group and 9 of 10 sera from the SjC23+IL-12 group were positive. The worm reduction rates in the SjC23 group and SjC23+IL-12 group were 26.9% and 35.4% respectively; the liver eggs reduction rates were 22.2% and 28.4%, respectively in comparison to the control group. This indicates that the pcDNA3.1-SjC23 DNA vaccine can induce partial protection against Schistosoma japonicum infection in C57BL/6 mice.