Comparison of the immune response elicited by a free peptide and a lipopeptide construct.

Among the synthetic peptides derived from the 28-kDa Schistosoma mansoni gluthatione-S-transferase (Sm28GST), the C-terminal peptide, comprising amino acid residues 190 to 211, represents a major T-cell epitope in both infected humans and Sm28GST-immunized mice. The aim of this study was to determine the nature of the immune response induced by the 190-211 peptide coupled to a fatty acid (lipopeptide construction) in comparison to the free form. We explored B- and T-cell responses elicited by these two peptidic constructions in three different mouse strains (BALB/c, CBA/N and C57B1/6). For all strains, the addition of a lipid chain to the 190-211 peptide greatly modified its immunogenicity. The lipopeptide, compared to the free form, induced a greatly reduced antibody response against the peptide, whereas the production of messenger for cytokines was greatly increased after immunization with the lipopeptide. Immunization with peptide led mainly to a Th1-type cytokine profile following antigenic restimulation in vitro, while lipopeptide, in general, induced a mixed profile, and that occurred most significantly with the production of messengers for the protective cytokines IFN-gamma and IL-2, even without antigenic restimulations. This modification of immunogenicity of a peptide by the addition of a lipid chain could be of value in the development of efficient peptide vaccines.