A Modular Self-Assembling and Self-Adjuvanting Multiepitope Peptide Nanoparticle Vaccine Platform to Improve the Efficacy and Immunogenicity of BCG

After more than a century since its initial development, Bacille Calmette-Guérin (BCG) remains the only licensed vaccine against tuberculosis (TB). Subunit boosters are considered a viable strategy to enhance BCG efficacy, which often wanes in adolescence. While many studies on booster subunit vaccines have concentrated on recombinant proteins, here we developed a novel modular peptide-based subunit vaccine platform that is flexible, cold-chain independent and customizable to diverse circumstances and populations. Each individual peptide building block consists of a linear arrangement comprising a 15-leucine self-assembly inducer moiety, a Mycobacterium tuberculosis (Mtb) target epitope and an human leukocyte antigen E (HLA-E) binding moiety, with each moiety separated by a triple lysine spacer. The building blocks, in any combination, are able to form a multiepitope nanoparticle. Six Mtb epitopes were selected to produce the self-assembling and self-adjuvating peptide-based TB nano-vaccine candidate PNx6. In vivo vaccination-challenge experiments demonstrated that subcutaneous boost of parenteral BCG immunization with PNx6 significantly enhanced its immunogenicity and improved its protective efficacy in a murine model of TB by more than 5-fold. This study presents evidence that purely amphiphilic peptides self-assemble into self-adjuvating nanoparticles with appropriate size and morphology for TB vaccination with great potential for a multitude of other diseases.