CLONING, MOLECULAR CHARACTERIZATION, AND FUNCTIONAL-ACTIVITY OF SCHISTOSOMA-JAPONICUM GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE, A PUTATIVE VACCINE CANDIDATE AGAINST SCHISTOSOMIASIS-JAPONICA

We report the cloning, molecular characterization, and purification of functionally active recombinant glyceraldehyde-3-phosphate dehydrogen ase (GAPDH) from the human bloodfluke Schistosoma japonicum. The GAPDH homolog from the related species Schistosoma mansoni has shown correl ation of antibody titer to resistance to reinfection. A 1,164-bp cDNA (C1) was isolated from an S. japonicum lambdaZapII cDNA expression lib rary immunoscreened with hyperimmune rabbit serum raised against solub le adult S. japonicum proteins. The open reading frame of C1 encodes a protein of 338 amino acids exhibiting 90% identity to the amino acid sequence of S. mansoni GAPDH. The inferred molecular mass of the prote in is 36,589 daltons, and in vitro translation of the cDNA With [S-35] methionine produced a radiolabelled band of the predicted size. Antibo dies to C1 selected from hyperimmune rabbit serum by affinity purifica tion recognized an S. japonicum protein doublet of 37 kDa but did not cross-react with a corresponding protein in S. mansoni extracts. The S . japonicum GAPDH appears to be translated from a single mRNA encoded by a single-copy gene. After subcloning in the QIAexpress vector pQE-1 0 and subsequent expression, the recombinant protein was purified unde r nondenaturing conditions and shown to exhibit functional GAPDH enzym atic activity.