Molecular and serological characteristics of the glutathione S-transferases of Schistosoma japonicum and Schistosoma mansoni.

When aqueous extracts of Schistosoma japonicum and S. mansoni adult worms are passed over columns of glutathione-conjugated agarose, two molecular species of Mr 26,000 and Mr 28,000 are detected in eluates as analysed by SDS-PAGE, these eluates having glutathione S-transferase (GST) activity. The molecules, termed Sj26 and Sj28 from S. japonicum and Sm26 and Sm28 from S. mansoni, can be immunogenic in rabbits or mice and appear not to be linked together as subunits of GST heterodimers. The elution profile of SjGST (Sj26+Sj28) from glutathione columns resembles that of SmGST (Sm26+Sm28) and, by peptide mapping, radioiodinated Sj26 and Sm26 are related as are the two Mr 28,000 molecules. Similarities between radioiodinated Sj28 and Sm28 are also obvious on two-dimensional gel electrophoresis with some differences being observed between Sj26 and Sm26. The Mr 28,000 molecules are more prominent than the Mr 26,000 molecules and, although Sj28 and Sm28 is a poor immunogen in mice, immunological cross-reactivity between Sj28 and Sm28 is generally more readily detected than that between Sj26 and Sm26. Whether experimental vaccination against schistosomiasis japonica and schistosomiasis mansoni reported with cloned GSTs can be improved by incorporation of both Mr 28,000 and Mr 26,000 species into the vaccine remains to be determined. On this point, the present data suggest that vaccination of mice with Sj26 plus Sm28 should be a useful means of increasing antibody responses to the GSTs of S. japonicum.