Improvement of the T-cell response to a non-immunogenic peptide by its tandem association with a highly efficient T-helper peptide

The 45–69 peptide, an helper T-cell epitope derived from HIV nef protein, is strongly immunogenic. A T-cell proliferative response was observed following immunization of Lou/M rats with 45–69 peptide administered in low dose and without any adjuvant. It is already known that the T-cell response to the 115–131 peptide of Sm28GST antigen, a protein of the parasite Schistosoma mansoni, requires the presence of a carrier or the use of peptidic constructs. We demonstrate here that a T-cell response against the 115–131 peptide can be obtained in the absence of adjuvant using peptidic constructs (115-45 and 45–115 peptides) resulting from tandem synthesis of 115–131 and 45–69 peptides. A covalent association of both peptides is necessary, since the co-injection of 45–69 and 115–131 peptides is not sufficient to induce a detectable anti-115–131 T-cell response. The mutual orientation between the respective tandem peptides (45–115 and 115-45) is critical for the T-cell response. These peptidic constructs possess distinct properties of antigenicity and immunogenicity but both allowed to reveal the existence of a 115–131 specific T-cell response normally undetectable using 115–131 peptide alone. This immunopharmacological approach should be useful in the rational design and construction of vaccines.