A simple screening method for detecting bindings between oligopeptides andHLA-DR molecules on filter papers: Possible application for mapping of putative helper T-cell epitopes on MSP1 of Plasmodium falciparum

Binding capacities of synthetic peptides to HLA-DR molecules were tested on filter papers to identify putative helper T-cell epitopes on a malarial pr otein. The antigen tested was the merozoite surface glycoprotein 1 (MSP1) o f Plasmodium falciparum, a vaccine candidate targeting the asexual erythroc ytic stage. Bindings between synthetic oligopeptides and HLA-DR molecules w ere tested. Such bindings were not nonspecific, and a known helper T-cell e pitope peptide showed positive binding to the restricting HLA-DR molecule. By using this screening system, we observed the unequal distribution of HLA -DR-binding peptides in 10 out of 17 MSP1 blocks tested. Block #6 of MSP1 s eemed to show the highest frequency in the positive binding; on the other h and, blocks #1 and #17, both of which were thought to be vaccine candidate regions, contained fewer HLA-DR binding peptides, This was not inconsistent with the results that block #17 was less stimulatory to peripheral T cells than block #6, The peptides with positive binding to HLA-DR showed actual epitope activities when we tested peptide-driven proliferation of human bul k T-cell lines, and association between the two parameters was statisticall y significant (P<0.001). For more detailed information for vaccine developm ent, peptides with both IgG- and HLA-DR binding activities were mapped in b lock #17 of MSP1. Together with these results, we demonstrate that our simp le screening system seems to provide essential information for vaccine deve lopment through uncovering locations of putative epitopes for human helper T cells.