Human T cell epitope mapping of the Schistosoma mansoni 14-kDa fatty acid-binding protein using cells from patients living in areas endemic for schistosomiasis

Abstract

he development of a defined anti-schistosomiasis vaccine would contribute to the current control strategy mainly because immunization provides long-lasting immunity to the disease. Sm14, one of the six Schistosoma mansoni antigens selected by WHO as a candidate to compose a subunit vaccine against schistosomiasis, has been associated with resistance to S. mansoni infection in human beings and is able to induce protection in the murine model. To identify human T cell epitopes in Sm14, we used the TEPITOPE algorithm to select peptides that would most likely bind to several HLA-DR molecules. In this study, three Sm14 epitopes were selected and produced as synthetic peptides. Human T cell responses from schistosomiasis patients living in endemic areas in Brazil were determined by proliferation assay and IL-5 and IFN-γ measurements. Differential peptide recognition and cytokine production in response to Sm14 epitopes were observed in individuals resistant to S. mansoni infection versus susceptible individuals. Sm14(32-48) and Sm14(53-69) peptides were preferentially recognized by peripheral blood mononuclear cells (PBMCs) of S. mansoni-resistant individuals, and Sm14(53-69) induced significant production of IFN-γ. Additionally, Sm14(32-48) and Sm14(53-69) were “promiscuous” peptides, since they were able to induce cellular immune responses in individuals carrying 10 and 8, respectively, of the 11 HLA-DR molecules expressed in the studied population. Among Sm14 synthetic peptides tested in this study, we identified Sm14(32-48) and Sm14(53-69) as promising candidates to compose an anti-schistosomiasis vaccine, since they seem to be related to resistance to human schistosomiasis.