Immunogenicity of polyepitope libraries assembled by epitope shuffling: an approach to the development of chimeric gene vaccination against malaria.
Developing a polyepitope vaccine which contains diverse antigenic types is a promising strategy to cope with the problem of malaria variation and diversity. However, arranging the peptides to produce the most effective immunogenicity remains a hurdle. In an attempt to develop an effective complex antigenic gene vaccine, we constructed a polyepitope library by randomly assembling epitopes using the epitope shuffling technique. The polyepitope library, which contains epitopes from different antigens of Plasmodium falciparum, was divided into five sub-libraries based on the size of chimeric genes. Here we report that higher antibody titers were observed in mice with immunized with sub-libraries containing genes >1200 bp, using enzyme-linked immunosorbent assay (ELISA) and indirect immunofluorescence (IFAT) assay to determine both individual epitope peptides and the natural parasites at the erythrocyte stage. Different levels of IgG subtypes and cytokines were elicited by different sub-library and administration times. In a rodent malaria model, some groups of immunized mice were partially cross-protected against a lethal challenge from Plasmodium yoelii. These results suggest that the immunogenicity of a polyepitope chimeric antigen is essentially conformation- and length-dependent, and demonstrates that the promising advantage of epitope shuffling technology is that it allows us to randomly assemble many polyepitope molecules in tandem format. This finding also indicates that polyepitope library vaccination is a suitable approach for screening optimized chimeric gene vaccines against malaria and other diseases.