Application and limitations of the multiple antigen peptide (MAP) system in the production and evaluation of anti-peptide and anti-protein antibodies.

The multiple antigen peptide (MAP) system has been proposed as a novel and valuable approach for eliciting antibodies to peptides and developing synthetic vaccines. The MAP system consists of a small immunogenically inert core matrix of lysine residues with alpha- and epsilon-amino groups for anchoring multiple copies of the same or different synthetic peptides. Several MAP systems, each containing eight copies of 6-15 residue-long peptides derived from the terminal and central regions of various proteins were analyzed in this study. The immunogenicity of MAPs was compared to that of the same peptides linked to carrier protein by means of conventional conjugation procedures. The various peptide antisera were tested in ELISA with homologous peptides conjugated to a carrier protein via their C terminal (as in the MAP system) or their N terminal end, or with their parent proteins. The antigenic properties of MAPs were studied with anti-peptide sera obtained by classical methods and with anti-protein sera. The results showed that the MAP system was an efficient antigen in ELISA except when the peptide corresponded to a C terminal epitope. However, the value of MAPs for raising anti-peptide antibodies cross-reactive with the cognate protein appeared much more limited. In the case of one N terminal peptide, the MAP construction was not immunogenic while the conventionally conjugated peptide induced antibodies that reacted strongly with the corresponding protein. In the case of the two C terminal peptides tested, the antibodies raised against MAP constructs reacted well with homologous MAPs but did not cross-react with the whole protein. Only in the case of a peptide from an internal domain of histone H2A did immunization with a MAP generate antibodies that cross-reacted with the protein.