Mr 26,000 antigen of Schistosoma japonicum recognized by resistant WEHI 129/J mice is a parasite glutathione S-transferase.

Mice of the inbred strain 129/J bred at this Institute (WEHI 129/J) are relatively resistant to chronic infection with the parasitic helminth Schistosoma japonicum. In contrast to more permissive mouse strains such as BALB/c, the WEHI 129/J mice are high responders to a Mr 26,000 adult worm antigen designated Sj26. Cloned cDNAs corresponding to Sj26 have been identified in a S. japonicum phage lambda gt11 amp3 expression library, and their nucleotide sequences have been deduced. The predicted amino acid sequence of the antigen specified by these cDNAs shows striking homology with class mu isozymes of mammalian glutathione S-transferases (RX:glutathione R-transferase, EC 2.5.1.18). Extracts of adult worms contain glutathione S-transferase activity, and affinity chromatography of enzyme activity on glutathione columns leads to the purification of a Mr 26,000 molecule that comigrates with Sj26. Although vaccination studies in mice with a beta-galactosidase-Sj26 fusion protein from Escherichia coli are encouraging, more immunogenic preparations of the antigen are likely to be required to establish the utility of Sj26 as a model vaccine.