RESUMEN
DNA technology has emerged as a promising route to accelerated manufacture of sequence agnostic vaccines. For activity, DNA vaccines must be protected and delivered to the correct antigen presenting cells. However, the physicochemical properties of the vector must be carefully tuned to enhance interaction with immune cells and generate sufficient immune response for disease protection. In this study, we have engineered a range of polymer-based nanocarriers based on the poly(beta-amino ester) (PBAE) polycation platform to investigate the role that surface poly(ethylene glycol) (PEG) density has on pDNA encapsulation, formulation properties and gene transfectability both in vitro and in vivo. We achieved this by synthesising a non-PEGylated and PEGylated PBAE and produced formulations containing these PBAEs, and mixed polyplexes to tune surface PEG density. All polymers and co-formulations produced small polyplex nanoparticles with almost complete encapsulation of the cargo in all cases. Despite high gene transfection in HEK293T cells, only the fully PEGylated and mixed formulations displayed significantly higher expression of the reporter gene than the negative control in dendritic cells. Further in vivo studies with a bivalent SARS-CoV-2 pDNA vaccine revealed that only the mixed formulation led to strong antigen specific T-cell responses, however this did not translate into the presence of serum antibodies indicating the need for further studies into improving immunisation with polymer delivery systems.
RESUMEN
The concept of a therapeutic cancer vaccine to activate anti-tumour immunity pre-dates innovations in checkpoint blockade immunotherapies. However, vaccination strategies have yet to show the hoped-for successes in patients, and unanswered questions regarding the underlying immunological mechanisms behind cancer vaccines have hampered translation to clinical practice. Recent advances in our understanding of the potential of tumour mutational burden and neo-antigen-reactive T cells for response to immunotherapy have re-ignited enthusiasm for cancer vaccination strategies, coupled with the development of novel mRNA-based vaccines following successes in prevention of COVID-19. Here we summarise current developments in cancer vaccines and discuss how advances in our comprehension of the cellular interplay in immunotherapy-responsive tumours may inform better design of therapeutic cancer vaccines, with a focus on the role of dendritic cells as the orchestrators of anti-tumour immunity. The increasing number of clinical trials and research being funnelled into cancer vaccines has demonstrated the 'proof-of-principle', supporting the hypothesis that therapeutic vaccines have potential as an immuno-oncology agent. For efficacious and safe cancer vaccines to be developed, better understanding of the underpinning immunological mechanisms is paramount.
