Synthesis of multiple antigenic peptides (MAPs)-strategies and limitations

Dendrimeric platforms such as MAPs can be synthesized either entirely by solid-phase methods (SPPS, direct approach) or by conjugation in solution of preformed, SPPS-made building blocks (indirect approach). Although MAPs and MAP-like constructs have been extensively and successfully used for various biological (mainly immunological) applications, experimental reports are most often lacking in chemical detail about their preparation and characterization. Here, we provide complete accounts of the synthesis and analytical documentation of MAPs and similar dendrimers by either all-SPPS (direct) or chemoselective thioether ligation (indirect) methods. We have chosen as model epitopes a 24-residue sequence of the ectodomain of protein M2 from influenza virus (M2e), which is found to be a rather challenging peptide epitope, and a far more manageable, shortened (12-residue) version of the same peptide. The advantages and shortcomings of both direct and indirect methods are discussed.