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A Simple Screening Method for Detecting Bindings between Oligopeptides and HLA‐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 protein. The antigen tested was the merozoite surface glycoprotein 1 (MSP1) of Plasmodium falciparum, a vaccine candidate targeting the asexual erythrocytic stage. Bindings between synthetic oligopeptides and HLA‐DR molecules were tested. Such bindings were not non‐specific, and a known helper T‐cell epitope 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 seemed to show the highest frequency in the positive binding; on the other hand, 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 bulk T‐cell lines, and association between the two parameters was statistically significant (P < 0.001). For more detailed information for vaccine development, peptides with both IgG‐ and HLA‐DR binding activities were mapped in block #17 of MSP1. Together with these results, we demonstrate that our simple screening system seems to provide essential information for vaccine development through uncovering locations of putative epitopes for human helper T cells.