Persistence of cellular and humoral response to synthetic peptides from definedPlasmodium falciparumantigens

The cellular and humoral immune responses to synthetic peptides reproducing the repeat sequences of two major vaccine candidates (circumsporozoite protein and Pfl55/RESA) were investigated in two groups of African subjects according to the length of their stay outside endemic areas. The relation between the lymphoproliferative response and the antibody levels to these antigens was studied. The results confirm the existence of T-cell epitopes within the repeat sequences of the CS protein and the Pfl55/RESA capable of inducing lymphocyte proliferation. Cellular response to all studied peptides was more frequently observed in individuals living in France for less than one year than in individuals living in France for a longer time. T-cell proliferation in the presence of the tetrapeptide and of the octapeptide from the C-terminus repeat of Pfl55/RESA was related, with an immunodominance of the tetrapeptide over the octapeptide. Cellular responses to the CS protein repeat and to the 11-amino-acid peptide from the Pfl55/RESA N-terminus were the longest lasting after termination of exposure. In a given individual, cellular and humoral responses were not related for any peptide studied.