Peptide-based vaccines would appear as the ideal alternative to conventional (e.g., inactivated whole-virus) vaccines, because they are safe (no infectious agent involved), versatile (readily adaptable to emergent outbreaks) and cost-effective (reliable, reproducible production and scale-up by chemical synthesis; simple storage and transport). These advantages are however offset by problems such as the difficulty in definition and chemical reproduction of epitopes, the usually low immunogenicity of peptides, or the often intricate relation between host-pathogen interaction and immune response, all of which partly explains why only a handful of peptide vaccines have attained therapeutic status.
Among the different pathogens targeted by peptide vaccines, foot-and-mouth disease virus (FMDV), arguably the economically most devastating animal disease worldwide, has received considerable attention. We have recently described vaccine candidates, generically known as BnT, consisting of a T-cell epitope branching out via a Lys tree into multiple (n= 2, 4) copies of a B-cell epitope.1,2 This particular arrangement of B and T epitopes on a single molecular platform is shown to confer full protection against FMDV challenge in both swine and cattle.3 Our presentation will illustrate various important aspects in the development of this synthetic vaccine, particularly issues such as epitope orientation and multiplicity,4 chemical ligation methods5 or adjuvanticity as well as provide insights on the uptake of the peptide by immune cells and on its in vivo localization.