Synthesis of a diepitope multiple antigen peptide containing sequences from two malaria antigens using Fmoc chemistry

Abstract

Multiple antigen peptides (MAP) consist of lysine residue cores with branching peptide arms and have been demonstrated to be efficient immunogens as well as useful antigens for ELISA. Synthesis of diepitope MAPs with two different branching peptides has previously been described using combined Boc and Fmoc chemistry. Here, the synthesis of a tetrameric diepitope MAP based on Fmoc chemistry is described. A lysine core was synthesized with N alpha- and N epsilon-amino groups othogonally protected by Fmoc and a recently described protection group, Dde, respectively. On the N alpha-amino groups, a sequence from the Plasmodium falciparum antigen Pf332 was synthesized with a capped N-terminus. After removal of Dde, a sequence from the P. falciparum circumsporozoite protein was synthesized on the core. Amino acid analysis of the MAP displayed equimolar amounts of the two peptide sequences, indicating the reliability of the protection group Dde. In ELISA, antibodies specific for either of the two malarial sequences reacted with the MAP. The major advantages of this approach for synthesis of diepitope MAPs are that only a panel of Fmoc-amino acid derivatives is required and that the more complicated cleavage procedure for Boc chemistry can be avoided.