IMMUNOGENICITY OF GENETICALLY-ENGINEERED GLUTATHIONE-S-TRANSFERASE FUSION PROTEINS CONTAINING A T-CELL EPITOPE FROM DIPHTHERIA-TOXIN

Glutathione S-transferase (GST) has been shown to induce a marginal an tibody response in experimental animals as well as partial protection against a number of parasitic worms, including Schistosoma and Fasciol a species, The objective of our study was to increase the immunogenici ty of GST by adding heterologous T-cell epitopes at the carboxy termin us of the protein. We generated recombinant GST proteins by attaching one or three tandem repeats of a T-cell epitope of CRM(197), a nontoxi c variant of diphtheria toxin, This T-cell epitope encoding the region of amino acids 366 to 383 of CRM(197), when contained in a GST fusion protein and/or after purification as a recombinant peptide, retained the ability to induce a CRM(197)-specific T-cell response, The fusion protein containing a single T-cell epitope induced a strong T-cell pro liferative response to GST and also enhanced anti-GST antibody product ion in mice. The addition of three repeats of the epitope did not augm ent the responses when compared with the responses of GST itself, The results suggest that the addition of a single T-cell epitope to a larg er protein like GST increases the immunogenicity of the protein,