Variable linking region immunogenicity using malarial peptide carrier protein conjugates of defined composition.

Thirty-five overlapping peptides from both conserved and variable parts of the N-terminal region of a malarial merozoite surface antigen (MSA2) were synthesised using solid phase chemistry. All peptides were synthesised with an added N-terminal cysteine and purified by reverse-phase HPLC to facilitate coupling to a carrier protein diphtheria toxoid (DT) using the hetero-bifunctional reagent maleimidocaproloxysuccinimide (MCS). Mice were immunised with these peptide-DT conjugates using Freund's complete adjuvant (FCA). The immune response of these mice was tested against peptide hapten, carrier protein (DT) and the linking region itself, using enzyme-linked immunoassay (ELISA). Although there was great variation in the immune response to each part of the immunogen construct, no significant correlation could be seen between each set of responses.