To determine the possibility whether DNA vaccines pcDNA3/SjSDISP of Schistosoma japonicum to induce autoimmunity and immune tolerance in the vaccinated mice, the titer of the specific antibodies against SjSDISP and the production of the autoimmune antibodies, such as presence of anti-nuclear and anti-dsDNA antibodies in the vaccinated mice were detected by ELISA assay and the toxicity of the plasmid DNA was studied through the observation of the change in body weight and the pathological examination of the major organs in mice. It was found that the titer of the specific antibody against SjSDISP was 1∶400 as determined by ELISA, but no autoimmune antibody could detected. The difference of the body weight of mice between the experimental and the control groups was not significant. No abnormal results of histopathological examination were obtained in both groups. From these observations, it is clear that there is no evidence to show that DNA vaccine pcDNA3/SjSDISP can induce auto-immunity and immune tolerance in mice.

A 1 270 bp full-length cDNA fragment was obtained from the Schistosoma japonicum (Chinese strain) adult cDNA library after the 3′ and 5′ ends of the incomplete expression sequence tag (EST) of hypoxanthine-guanine phosphoribosyltransferase of Schistosoma japonicum (SjHGPRT) were amplified by the anchored PCR with 2 pairs of primer that were designed according to the published incomplete SjHGPRT EST and the sequence of multiclone sites of library ?gt11 vector. Sequence analysis indicated that this fragment, with an identity of 82% to hypoxanthine-guanine phosphoribosyltransferase of Schistosoma mansoni (SmHGPRT), contained a complete open reading frame(ORF). The deduced amino acid sequence showed 83% identity to that of SmHGPRT. This fragment was cloned into the prokaryotic expression vector pQE30, and subsequently sequenced and expressed in Escherichia coli. SDS-PAGE revealed that M of the recombinant protein was about 28 ku. Western-blot analysis showed that the recombinant protein was recognized by the polyclonal antisera from rabbits immunized with Schistosoma japonicum adult worm antigen. Mice vaccinated with recombinant protein revealed significant worm burden, liver eggs per gram (LEPG), fecal eggs per gram (FEPG) and intrauterine eggs of the female worms reduction percentage, compared with the controls. Taken together, the SjHGPRT full-length cDNA can be cloned and expressed in E.coli as a recombinant protein that elicited immunity against the challenge infection with Schistosoma japonicum, indicating its potential as a partial protection vaccine candidate.

A 1 270 bp full-length cDNA fragment was obtained from the Schistosoma japonicum (Chinese strain) adult cDNA library after the '3' and 5' ends of the incomplete expression sequence tag (EST) of hypoxanthine-guanine phosphoribosyltransferase of Schistosoma japonicum (SjHGPRT) were amplified by the anchored PCR with 2 pairs of primer that were designed according to the published incomplete SjHGPRT EST and the sequence of multiclone sites of library λgt1 1 vector. Sequence analysis indicated that this fragment, with an identity of 82% to hypoxanthine-guanine phosphoribosyltransferase ofSchistosoma mansoni (SmHGPRT), contained a complete open reading frame(ORF). The deduced amino acid sequence showed 83% identity to that of SmHGPRT. This fragment was cloned into the prokaryotic expression vector pQE30, and subsequently sequenced and expressed in Escherichia coli. SDS-PAGE revealed that M of the recombinant protein was about 28 ku. Western-blot analysis showed that the recombinant protein was recognized by the polyclonal antisera from rabbits immunized with Schistosoma japonicum adult worm antigen. Mice vaccinated with recombinant protein revealed significant worm burden, liver eggs per gram (LEPG), fecal eggs per gram (FEPG) and intrauterine eggs of the female worms reduction percentage, compared with the controls. Taken together, the SjHGPRT full-length cDNA can be cloned and expressed in E. coli as a recombinant protein that elicited immunity against the challenge infection with Schistosoma japonicum, indicating its potential as a partia1 protection vaccine candidate.