Orthogonal solid-phase synthesis of tetramannosylated peptide constructs carrying three independent branched epitopes

The development of peptide-based drugs requires the chemical synthesis of s ystems as complex as they appear in nature. Most bioactive peptides have to be associated with co-activators and delivery or targeting domains, the sy nthesis of such complexes is far from trivial. In efforts to develop a prot otype for a new generation of peptide vaccines, a peptide construct was pre pared, using an alternating lysine and glycine backbone. A 24-mer major ant igen corresponding to the M2 protein of influenza virus, and two shorter T- cell epitopes derived from the hemagglutinin were co-synthesized onto the s ide chains of the first three lysines. To help the delivery of the construc ts inside the antigen presenting cells via the multimeric cell surface mann ose receptor, three additional lysines were decorated with four mannosylate d serine residues. The synthesis difficulty increased upon addition of the glycoamino acids and alternating the peptide and glycoamino acid branches. The successful solid-phase synthesis of the constructs proceeded with the u se of a combination of three quasi-orthogonally removable amino protecting groups and a robust activation strategy. These multi-glycosylated construct s represent some of the most complex synthetic peptides to date, and will b e used to study the entire process of antigen delivery, presentation and im munogenicity. (C) 2001 Elsevier Science Ltd. All rights reserved.