Optimisation of peptide-based cytotoxic T-cell determinants using non-natural amino acids

Abstract

In this brief review we describe the methods that our group and others have developed in incorporating non-natural amino acids into peptide antigens, principally to increase protease resistance, for potential use in peptide-based vaccines. Peptide-based vaccination has the potential to generate protective immunity without the need forin situ antigen synthesis or further proteolytic processing of the antigen. The ability to deliver minimal T cell epitopes to the effector cells of the immune system also minimises unwanted side effects and simplifies clinical monitoring. The major hurdle in designing successful peptide-based vaccines resides in issues surrounding the delivery and stability of the peptide immunogen, as it is the form in which the epitope is delivered that will determine how it will be processed by the immune system and ultimately whether it will be capable of inducing an appropriate immune response. Thus, one of the confounding issues with peptide-based vaccines is their poor bioavailability, which is predominantly due to proteolysis and oxidative damage of the ‘naked’ peptide. Strategies that stabilise peptide epitopes promise to overcome the current problems and make peptide-based immunogens more applicable in vaccine design.