Epitopic characterization and vaccinal potential of peptides derived from a major antigen of Schistosoma mansoni (Sm28 GST).
The P28 antigen of Schistosoma mansoni has been shown to induce protective immunity against schistomiasis in rodents and primates. The analysis of the primary structure of the P28 molecule using various predictive algorithms led to the synthesis of seven peptides which were used to localize the major T cell epitopes of the P28. Two of these synthetic peptides (amino acids 24-43 and 115-131) were found to contain major T cell sites of the P28 antigen. Indeed, both 24-43 and 115-131 peptides stimulate T lymphocytes from Fischer rats and Balb/c mice immunized with the recombinant P28. Moreover, these localized moieties are exposed to the host's immune system during natural S. mansoni infection since they activate T cell populations of infected rats, mice and chronically infected Kenyan children. A multiple antigen peptide containing eight copies of peptide (MAP 115-131) has been prepared and used as immunogen in rats, mice and baboons. In all these models, the MAP 115-131 induces both humoral and cellular responses towards the P28. Preimmunization with the MAP 115-131 before a challenge with the whole P28 molecule increases T cell proliferation and antibody production. The active immunization of rats with the MAP 115-131 before a challenge with the whole P28 molecule increases the T cell proliferation and the antibody production. The active immunization of rats with the MAP 115-131 before challenge infection with the parasite achieved significant protection.